Document:

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                                                                     EXHIBIT 4.2
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                                WARRANT AGREEMENT

                                 BY AND BETWEEN

                               KOMAG, INCORPORATED

                                       AND

                               FLEET NATIONAL BANK
                             F/K/A BANKBOSTON, N.A.

                                BANK OF MONTREAL

                            BEAR, STEARNS & CO. INC.

                           COMERICA BANK - CALIFORNIA

                            OLYMPUS SECURITIES, LTD.

                              NELSON PARTNERS LTD.

                             THE BANK OF NOVA SCOTIA

                         UNION BANK OF CALIFORNIA, N.A.

                            LOEB PARTNERS CORPORATION

                        THE DAI-ICHI KANGYO BANK, LIMITED

                      THE INDUSTRIAL BANK OF JAPAN, LIMITED

                  THE MITSUBISHI TRUST AND BANKING CORPORATION

                              SANWA BANK CALIFORNIA

                                 BANK ONE, N.A.

                             THE FUJI BANK, LIMITED

                           THE SUMITOMO BANK, LIMITED

                            DATED AS OF JUNE 1, 2000

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                               TABLE OF CONTENTS*
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SECTION 1.  Warrant Certificates; Issuance of Warrants................................................................1

SECTION 2.  Execution of Warrant Certificates.........................................................................2

SECTION 3.  Registration..............................................................................................2

SECTION 4.  Registration of Transfers and Exchanges...................................................................2

SECTION 5.  Warrants; Exercise of Warrants............................................................................3

SECTION 6.  Payment of Taxes..........................................................................................5

SECTION 7.  Mutilated or Missing Warrant Certificates.................................................................5

SECTION 8.  Reservation of Warrant Shares; Rights.....................................................................5

SECTION 9.  Obtaining Stock Exchange Listings.........................................................................6

SECTION 10.  Adjustment of Exercise Price and Number of Warrant Shares Issuable.......................................6
             (a) Adjustment for Change in Capital Stock...............................................................6
             (b) Adjustment for Rights Issue..........................................................................7
             (c) Adjustment for Other Distributions...................................................................8
             (d) Adjustment for Common Stock Issue....................................................................8
             (e) Adjustment for Convertible Securities Issue.........................................................10
             (f) Current Market Price................................................................................11
                   (1) Current Market Price..........................................................................11
                   (2) Fair Market Value.............................................................................11
                   (3) Independent Expert............................................................................11
             (g) Consideration Received..............................................................................12
             (h) When De Minimis Adjustment May Be Deferred..........................................................12
             (i) When No Adjustment Required.........................................................................12
             (j) Notice of Adjustment................................................................................13
             (k) Voluntary Reduction.................................................................................13
             (l) Reorganization of Company...........................................................................13
             (m) When Issuance or Payment May Be Deferred............................................................14
             (n) Adjustment in Number of Shares......................................................................14
             (o) Form of Warrants....................................................................................15

SECTION 11.  Fractional Interests....................................................................................15
</TABLE>

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* This Table of Contents does not constitute a part of this Agreement or have
  any bearing upon the interpretation of any of its terms or provisions.

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<S>                                                                                                                <C>
SECTION 12.  Representations and Warranties to the Company...........................................................15
             (a) Corporate Organization..............................................................................15
             (b) Authorization.......................................................................................15
             (c) Governmental Consents...............................................................................16
             (d) Validity............................................................................................16
             (e) Not an Investment Company...........................................................................16
             (f) Reports.............................................................................................16
             (g) Authorized Shares...................................................................................17
             (h) Status of the Warrants and the Warrant Shares.......................................................17

SECTION 13.  Purchase for Investment; Authority; Binding Agreement...................................................17

SECTION 14.  Notices to Warrant Holders..............................................................................18

SECTION 15.  Notices to Company and Warrant Holder...................................................................19

SECTION 16.  Supplements and Amendments..............................................................................20

SECTION 17.  Successors..............................................................................................20

SECTION 18.  Governing Law...........................................................................................20

SECTION 19.  Benefits of This Agreement..............................................................................20

SECTION 20.  Counterparts............................................................................................20

SCHEDULE 1.............................................................................................................

EXHIBIT A..............................................................................................................

EXHIBIt B..............................................................................................................
</TABLE>

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               THIS WARRANT AGREEMENT (the "Agreement") is dated as of June 1,
2000, and entered into by and among Komag, Incorporated, a Delaware corporation
(the "Company"), and Fleet National Bank f/k/a BankBoston, N.A., Bank of
Montreal, Bear, Stearns & Co. Inc., Comerica Bank - California, Olympus
Securities, Ltd., Nelson Partners Ltd., The Bank of Nova Scotia, Union Bank of
California, N.A., Loeb Partners Corporation, The Dai-Ichi Kangyo Bank, Limited,
The Industrial Bank of Japan, Limited, The Mitsubishi Trust and Banking
Corporation, Sanwa Bank California, Bank One, N.A., The Fuji Bank, Limited, and
The Sumitomo Bank, Limited (collectively, "Banks").

               WHEREAS, the Banks have made loans and otherwise extended credit
in the aggregate outstanding principal amount of $260,000,000 to the Company
pursuant to certain existing credit facilities;

               WHEREAS, pursuant to a Loan Restructure Agreement dated as of the
date hereof (the "Loan Restructure Agreement"), Banks propose to restructure
such existing credit facilities (as so restructured, the "Credit Facilities");
and

               WHEREAS, to induce Banks to enter into the Loan Restructure
Agreement and to restructure such existing credit facilities, pursuant thereto
the Company proposes to issue to Banks, or their respective designees, Common
Stock Purchase Warrants as hereinafter described (the "Warrants"), to
collectively purchase common stock of the Company, $0.01 par value (the "Common
Stock") equal to, in the aggregate, 3.5% of the issued and outstanding Common
Stock (the Common Stock issuable on exercise of the Warrants being referred to
herein as the "Warrant Shares"), pursuant to this Agreement.

               NOW, THEREFORE, in consideration of the premises and the mutual
agreements herein set forth, the parties hereto agree as follows:

               SECTION 1. Warrant Certificates; Issuance of Warrants. The
certificates evidencing the Warrants (the "Warrant Certificates") to be
delivered to the Banks or their respective designees permitted as assignees
under the Loan Restructure Agreement, in the respective amounts set forth in
Schedule 1 hereto, pursuant to this Agreement shall be in registered form only
and shall be substantially in the respective forms set forth in Exhibits A and B
attached hereto.

               The Warrants shall be issuable as follows:

                   (a) Series A Warrants: The Series A Warrants shall be
exercisable into a number of shares of Common Stock equal to, in the aggregate,
2.5% of the issued and outstanding Common Stock as of the date of issuance of
the Warrants.

                   (b) Series B Warrants: The Series B Warrants shall be
exercisable into a number of shares of Common Stock equal to, in the aggregate,
1.0% of the issued and outstanding Common Stock as of the date of issuance of
the Warrants.

                                       1
<PAGE>   5
               SECTION 2. Execution of Warrant Certificates. Warrant
Certificates shall be signed on behalf of the Company by its Chairman of the
Board of Directors of the Company (the "Board") or its President or a Vice
President and by its Secretary or an Assistant Secretary under its corporate
seal. Each such signature upon the Warrant Certificates may be in the form of a
facsimile signature of the present or any future Chairman of the Board,
President, Vice President, Secretary or Assistant Secretary and may be imprinted
or otherwise reproduced on the Warrant Certificates and for that purpose the
Company may adopt and use the facsimile signature of any person who shall have
been Chairman of the Board, President, Vice President, Secretary or Assistant
Secretary, notwithstanding the fact that, at the time the Warrant Certificates
shall be delivered or disposed of, he shall have ceased to hold such office. The
seal of the Company may be in the form of a facsimile thereof and may be
impressed, affixed, imprinted or otherwise reproduced on the Warrant
Certificates.

               In case any officer of the Company who shall have signed any of
the Warrant Certificates shall cease to be such officer before the Warrant
Certificates so signed shall have been disposed of by the Company, such Warrant
Certificates nevertheless may be delivered or disposed of as though such person
had not ceased to be such officer of the Company; and any Warrant Certificate
may be signed on behalf of the Company by any person who, at the actual date of
the execution of such Warrant Certificate, shall be a proper officer of the
Company to sign such Warrant Certificate, although at the date of the execution
of this Warrant Agreement any such person was not such officer.

               SECTION 3. Registration. The Company shall number and register
the Warrant Certificates in a register as they are issued.

               SECTION 4. Registration of Transfers and Exchanges. The Company
shall from time to time register the transfer of any outstanding Warrant
Certificates in a Warrant register to be maintained by the Company upon
surrender of such Warrant Certificates accompanied by a written instrument or
instruments of transfer in form satisfactory to the Company, duly executed by
the registered holder or holders thereof or by the duly appointed legal
representative thereof or by a duly authorized attorney. Upon any such
registration of transfer, a new Warrant Certificate shall be issued to the
transferee(s) and the surrendered Warrant Certificate shall be canceled and
disposed of by the Company.

               The Warrant holders agree that each certificate representing
Warrant Shares will bear the following legend:

               THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN
               REGISTERED UNDER THE SECURITIES ACT OF 1933 OR THE SECURITIES
               LAWS OF ANY STATE AND MAY NOT BE SOLD OR OTHERWISE DISPOSED OF
               EXCEPT PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT UNDER SUCH
               ACT AND APPLICABLE STATE SECURITIES LAWS OR AN APPLICABLE
               EXEMPTION TO THE REGISTRATION REQUIREMENTS OF SUCH ACT OR SUCH
               LAWS. SUCH

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               SALE OR OTHER DISPOSITION MUST ALSO BE IN COMPLIANCE WITH THE
               RESTRICTIONS ON TRANSFER SET FORTH IN THE WARRANT AGREEMENT DATED
               AS OF JUNE 1 2000, AS MODIFIED OR SUPPLEMENTED FROM TIME TO TIME,
               A COPY OF WHICH MAY BE OBTAINED FROM KOMAG, INCORPORATED AT ITS
               PRINCIPAL EXECUTIVE OFFICE.

               Warrant Certificates may be exchanged at the option of the
holder(s) thereof, when surrendered to the Company at its office for another
Warrant Certificate or other Warrant Certificates of like tenor and representing
in the aggregate a like number of Warrants, and such holder(s) shall pay all
reasonable out-of-pocket expenses actually incurred by Company in connection
with such exchange. Warrant Certificates surrendered for exchange shall be
canceled and disposed of by the Company.

               SECTION 5. Warrants; Exercise of Warrants. Subject to the terms
of this Agreement, each holder of Series A Warrants shall have the right, which
may be exercised commencing as of the date hereof until 5:00 p.m., Los Angeles
time on June 1, 2010, to receive from the Company the number of fully paid and
nonassessable Warrant Shares which the holder may at the time be entitled to
receive on exercise of such Warrants and payment to the Company of the Exercise
Price (as defined below) then in effect for such Warrant Shares. Each Series A
Warrant not exercised prior to 5:00 p.m., Los Angeles time, on June 1, 2010
shall become void and all rights thereunder and all rights in respect thereof
under this Agreement shall cease as of such time. The Company shall notify each
holder of Series A Warrants in writing 90 days prior to the expiration of all
unexercised Series A Warrants, of the upcoming expiration of all such
unexercised Warrants.

               Subject to the terms of this Agreement, each holder of Series B
Warrants shall have the right, which may be exercised commencing at the opening
of business on June 1, 2001 and until 5:00 p.m., Los Angeles time on June 1,
2011, to receive from the Company the number of fully paid and nonassessable
Warrant Shares which the holder may at the time be entitled to receive on
exercise of such Warrants and payment to the Company of the Exercise Price then
in effect for such Warrant Shares. Each Series B Warrant not exercised prior to
5:00 p.m., Los Angeles time on June 1, 2011, shall become void and all rights
thereunder and all rights in respect thereof under this Agreement shall cease as
of such time. The Company shall notify each holder of Series B Warrants in
writing 90 days prior to the expiration of all unexercised Series B Warrants, of
the upcoming expiration of all such unexercised Warrants. Notwithstanding
anything to the contrary in this Agreement, the Series B Warrants shall become
void and all rights thereunder and all rights in respect thereof under this
Agreement shall cease if the unpaid loan balances on the notes issued pursuant
to the Credit Facilities, in the aggregate, does not exceed $160,000,000.

A Warrant may be exercised upon surrender to the Company at its office
designated for such purpose (the address of which is set forth in Section 14
hereof) of the certificate or certificates evidencing the Warrants to be
exercised with the form of election to purchase duly filled in and signed, which
signature shall be guaranteed by a bank or trust company having an

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office or correspondent in the United States or a broker or dealer which is a
member of a registered securities exchange or the National Association of
Securities Dealers, Inc., and upon payment to the Company of the exercise price
(the "Exercise Price") which is set forth in the applicable form of Warrant
Certificate attached here as Exhibit A or B, respectively, subject to adjustment
pursuant to Section 10, for the number of Warrant Shares in respect of which
such Warrants are then exercised. For Warrants exercised within two years of
their date of issuance, payment of the aggregate Exercise Price shall be made,
in lieu of any cash payment, by surrendering such Warrants in exchange for a
number of Warrant Shares equal to the product of (x) the number of Warrant
Shares issuable upon exercise of the Warrants being surrendered multiplied by
(y) a fraction, the numerator of which is the Current Market Price (determined
in accordance with Section 10(f) hereof) of the Warrant Shares less the Exercise
Price, and the denominator of which is such Current Market Price (the surrender
of Warrants in lieu of any cash payment is hereinafter referred to as a
"Cashless Exercise"). For Warrants exercised after two years from their date of
issuance, payment of the aggregate Exercise Price shall be made (i) in cash or
by immediately available funds payable to the order of the Company or (ii) by a
Cashless Exercise.

               Upon such surrender of Warrants and payment of the Exercise
Price, the Company shall, at its sole cost and expense, issue and cause to be
delivered with all reasonable dispatch to or upon the written order of the
holder and in such name or names as the Warrant holder may designate, a
certificate or certificates for the number of full Warrant Shares issuable upon
the exercise of such Warrants together with cash as provided in Section 11;
provided, however, that if any reclassifications, consolidation, merger or lease
or sale of assets is proposed to be effected by the Company as described in
subsection (1) of Section 10 hereof, or a tender offer or an exchange offer for
shares of Common Stock of the Company shall be made, upon such surrender of
Warrants and payment of the Exercise Price as aforesaid, the Company shall, as
soon as possible, but in any event not later than five business days thereafter,
issue and cause to be delivered the full number of Warrant Shares issuable upon
the exercise of such Warrants in the manner described in this sentence together
with cash as provided in Section 11. Such certificate or certificates shall be
deemed to have been issued and any person so designated to be named therein
shall be deemed to have become a holder of record of such Warrant Shares as of
the date of the surrender of such Warrants and payment of the Exercise Price.

               The Warrants shall be exercisable, at the election of the holders
thereof, either in full or from time to time in part; provided, however, that no
partial exercise shall be for an amount less than 2,000 Warrant Shares or, if
less, the total number of Warrant Shares purchasable by the exercising holder.
In the event that a certificate evidencing Warrants is exercised in respect of
fewer than all of the Warrant Shares issuable on such exercise at any time prior
to the date of expiration of the Warrants, a new certificate evidencing the
remaining Warrant or Warrants will be issued and delivered pursuant to the
provisions of this Section and Section 2 hereof.

All Warrant Certificates surrendered upon exercise of Warrants shall be canceled
and disposed of by the Company. The Company shall keep copies of this Agreement
and any notices given or received hereunder available for inspection by the
holders during normal business hours

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at its office or such other place as the Company may from time to time designate
by written notice to the holders.

               SECTION 6. Payment of Taxes. The Company will pay all stamp,
documentary, transfer or similar taxes attributable to the initial issuance of
the Warrants and the Warrant Shares upon the exercise of Warrants.

               SECTION 7. Mutilated or Missing Warrant Certificates. In case any
of the Warrant Certificates shall be mutilated lost, stolen or destroyed, the
Company shall issue, in exchange and substitution for and upon cancellation of
the mutilated Warrant Certificate, or in lieu of and substitution for the
Warrant Certificate lost, stolen or destroyed, a new Warrant Certificate of like
tenor and representing an equivalent number of Warrants, but only upon receipt
of evidence reasonably satisfactory to the Company of such loss, theft or
destruction of such Warrant Certificate and indemnity also reasonably
satisfactory to it. Applicants for such substitute Warrant Certificates shall
also comply with such other reasonable regulations as the Company may prescribe
and shall pay all reasonable out of pocket expenses actually incurred by Company
in connection with any such exchange and substitution described in this Section
7.

               SECTION 8. Reservation of Warrant Shares; Rights. The Company
will at all times reserve and keep available free from preemptive rights, out of
the aggregate of its authorized but unissued Common Stock or its authorized and
issued Common Stock held in its treasury, for the purpose of enabling it to
satisfy any obligation to issue Warrant Shares upon exercise of Warrants, the
maximum number of shares of Common Stock which may then be deliverable upon the
exercise of all outstanding Warrants.

               The Company shall issue, together with each Warrant Share issued
upon exercise of a Warrant, any rights issued to holders of Common Stock in
addition thereto or in replacement therefor, whether or not such rights shall be
exercisable at such time, but only if such rights are issued and outstanding and
held by other holders of Common Stock at such time and have not expired.

               The Company or, if appointed, the transfer agent for the Common
Stock (the "Transfer Agent") and every subsequent transfer agent for any shares
of the Company's capital stock issuable upon the exercise of any of the rights
of purchase aforesaid will be irrevocably authorized and directed at all times
to reserve such number of authorized shares as shall be required for such
purpose. The Company will keep a copy of this Agreement on file with the
Transfer Agent and with every subsequent transfer agent for any shares of the
Company's capital stock issuable upon the exercise of the rights of purchase
represented by the Warrants. The Company will furnish such Transfer Agent a copy
of all notices of adjustments and certificates related thereto, transmitted to
each holder pursuant to Section 14 hereof.

Before taking any action which would cause an adjustment pursuant to Section 10
hereof to reduce the Exercise Price below the then par value (if any) of the
Warrant Shares, the Company will take any corporate action which may, in the
opinion of its counsel, be necessary in

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order that the Company may validly and legally issue fully paid and
nonassessable Warrant Shares at the Exercise Price as so adjusted.

               SECTION 9. Obtaining Stock Exchange Listings. The Company will
from time to time take all action which may be necessary so that the Warrant
Shares, immediately upon their issuance upon the exercise of Warrants, will be
listed or quoted on the principal securities exchanges and markets within the
United States of America, if any, on which other shares of Common Stock are then
listed.

               SECTION 10. Adjustment of Exercise Price and Number of Warrant
Shares Issuable. The Exercise Price and the number of Warrant Shares issuable
upon the exercise of each Warrant are subject to adjustment from time to time
upon the occurrence of the events enumerated in this Section 10. For purposes of
this Section 10, "Common Stock" means shares now or hereafter authorized of any
class of common stock of the Company and any other stock of the Company, however
designated, that has the right (subject to any prior rights of any class or
series of preferred stock) to participate in any distribution of the assets or
earnings of the Company without limit as to per share amount.

               (a) Adjustment for Change in Capital Stock.

                   If the Company:

                   (1) pays a dividend or makes a distribution on its Common
               Stock in shares of its Common Stock;

                   (2) subdivides its outstanding shares of Common Stock into a
               greater number of shares; or

                   (3) combines its outstanding shares of Common Stock into a
               smaller number of shares;

then the Exercise Price in effect immediately prior to such action shall then be
adjusted in accordance with the formula:

                                            O
                                 E' = E x  ----
                                            A
where:
                      E' =          the adjusted Exercise Price

                      E =           the current Exercise Price

                      O =           the number of Shares of Common Stock
                                    outstanding prior to such action

                      A =           the number of shares of Common Stock
                                    outstanding immediately after such action

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<PAGE>   10
               In the case of a dividend or distribution, the adjustment shall
become effective immediately after the record date for determination of holders
of shares of Common Stock entitled to receive such dividend or distribution, and
in the case of a subdivision or combination, the adjustment shall become
effective immediately after the effective date of such corporate action.

               If after an adjustment a holder of a Warrant upon exercise of it
may receive shares of two or more classes of capital stock of the Company, the
Company shall determine the allocation of the adjusted Exercise Price between
the classes of capital stock. After such allocation, the exercise privilege, the
number of shares issuable upon such exercise, and the Exercise Price of each
class of capital stock shall thereafter be subject to adjustment on terms
comparable to those applicable to Common Stock in this Section 10.

               Such adjustment shall be made successively whenever any event
listed above shall occur in accordance with this Section 10(a).

          (b)  Adjustment for Rights Issue.

               If the Company distributes any rights, options or warrants to any
holder of its Common Stock entitling such holder at any time after the record
date mentioned below to purchase shares of Common Stock at a price per share
less than the current market price per share on that record date, the Exercise
Price shall be adjusted in accordance with the formula:

                                     O  +  N x P
                                           -----
                     E' = E    x             M
                                   ---------------
                                        O + N
where:
                      E' =    the adjusted Exercise Price.

                      E =     the current Exercise Price.

                      O =     the number of Shares of Common Stock outstanding
                              on the record date.

                      N =     the number of additional shares of Common Stock
                              issuable upon exercise of the rights, options or
                              warrants offered.

                      P =     the exercise price per share of the additional
                              shares issuable upon exercise of the rights,
                              options or warrants.

                      M =     the current market price per share of Common
                              Stock on the record date.

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<PAGE>   11
               The adjustment shall be made successively whenever any such
rights, options or warrants are issued and shall become effective immediately
after the record date for the determination of stockholders entitled to receive
the rights, options or warrants. If at the end of the period during which such
rights, options or warrants are exercisable, not all rights, options or warrants
shall have been exercised, the Exercise Price shall be immediately readjusted to
what it would have been if "N" in the above formula had been the number of
shares actually issued.

          (c)  Adjustment for Other Distributions.

               If the Company distributes to any holder of its Common Stock any
of its assets (including but not limited to securities and cash), debt
securities, capital stock, or any rights or warrants to purchase assets, debt
securities, capital stock, or other securities of the Company, the Exercise
Price shall be adjusted in accordance with the formula:

                                         M  -  F
                               E' = E x  -------
                                           M

where:

                      E' =    the adjusted Exercise Price.

                      E  =    the current Exercise Price.

                      M  =    the current market price per share of Common
                              Stock on the record date mentioned below.

                      F  =    the Fair Market Value (as defined in Section
                              10(f)) on the record date of the assets, debt
                              securities, capital stock, rights or warrants or
                              other securities applicable to one share of Common
                              Stock.

               The adjustment shall be made successively whenever any such
distribution is made and shall become effective immediately after the record
date for the determination of stockholders entitled to receive the distribution.

               This subsection does not apply to (i) dividends, distributions,
subdivisions, or combinations referred to in subsection (a) of this Section 10,
(ii) rights, options or warrants referred to in subsection (b) of this Section
10, or (iii) ordinary course quarterly cash dividends distributed to all holders
of Common Stock.

            (d) Adjustment for Common Stock Issue.

               If the Company issues shares of Common Stock for a consideration
per share less than the current market price per share of Common Stock on the
date the Company fixes the offering price of such additional shares, the
Exercise Price shall be adjusted in accordance with the formula:

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<PAGE>   12
                                           P
                                       O + --
                                           M
                       E' =  E  x   ---------------
                                           A

where:

                      E' =    the adjusted Exercise Price.

                      E  =    the current Exercise Price.

                      O  =    the number of shares outstanding immediately
                              prior to the issuance of such additional shares.

                      P  =    the aggregate consideration received for issuance
                              of such additional shares.

                      M  =    the current market price per share of Common
                              Stock on the date of issuance of such additional
                              shares.

                      A  =    the number of shares outstanding immediately
                              after the issuance of such additional shares.

               The adjustment shall be made successively whenever any such
issuance is made, and shall become effective immediately after such issuance.

               This subsection (d) does not apply to:

               (1) rights, options, warrants or other distributions referred to
           in subsections (b), (c) or (e) of this Section 10,

               (2) Common Stock issued to the Company's directors, employees and
           non-employee service providers under bona fide benefit plans, if such
           Common Stock would otherwise be covered by this subsection (d), or

               (3) Common Stock issued in a bona fide underwritten public
           offering.

           (e)  Adjustment for Convertible Securities Issue.

                If the Company issues any securities convertible into or
exchangeable for Common Stock (other than securities issued in transactions
described in subsections (b) and (c) of this Section 10) for a consideration per
share of Common Stock initially deliverable upon conversion or exchange of such
securities less than the current market price per share of Common Stock on the
date of issuance of such securities, the Exercise Price shall be adjusted in
accordance with this formula:

                                       9
<PAGE>   13
                                            P
                                     O  +  --
                                            M
                       E' =  E  x    -------------
                                     O  +   D

where:

                      E' =    the adjusted Exercise Price.

                      E  =    the then current Exercise Price.

                      O  =    the number of shares outstanding immediately
                              prior to the issuance of such additional shares.

                      P  =    the aggregate consideration received for
                              issuance of such securities.

                      M  =    the current market price per share of Common
                              Stock on the date of issuance of such securities.

                      D  =    the maximum number of shares deliverable upon
                              conversion or in exchange for such securities at
                              the initial conversion or exchange rate.

               The adjustment shall be made successively whenever any such
issuance is made, and shall become effective immediately after such issuance.

               If all of the Common Stock deliverable upon conversion or
exchange of such securities have not been issued when such securities are no
longer outstanding, then the Exercise Price shall promptly be readjusted to the
Exercise Price which would then be in effect had the adjustment upon the
issuance of such securities been made on the basis of the actual number of
shares of Common Stock issued upon conversion or exchange of such securities.

          (f)  Current Market Price.

               (1) Current Market Price. In subsections (b), (c), (d) and (e) of
          this Section 10, the current market price per share of Common Stock on
          any date is:

                   (i) if the Common Stock is not registered under the
          Securities Exchange Act of 1934, as amended (the "Exchange Act"), then
          the Fair Market Value of the Common Stock based upon the Fair Market
          Value of 100% of the Company if sold as a going concern and without
          regard to any discount for the lack of liquidity or on the basis that
          the relevant shares of the Common Stock do not constitute a majority
          or controlling interest in the Company; or

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<PAGE>   14
                   (ii) if the Common Stock is registered under the Exchange
          Act, the average of the Quoted Prices of the Common Stock for no fewer
          than 10 consecutive trading days during a period of no more than 20
          consecutive trading days ending on the date in question. The "Quoted
          Price" of the Common Stock is the last reported sales price of the
          Common Stock as reported by NASDAQ National Market, or if the Common
          Stock is listed on a national securities exchange, the last reported
          sales price of the Common Stock on such exchange (which shall be for
          consolidated trading if applicable to such exchange), or if neither so
          reported or listed, the last reported bid price of the Common Stock.
          In the absence of one or more such quotations, the current market
          price of the Common Stock shall be determined as if the Common Stock
          was not registered under the Exchange Act.

               (2) Fair Market Value. Fair Market Value means the value
          obtainable upon a sale in an arm's-length transaction to a third party
          under usual and normal circumstances, with neither the buyer nor the
          seller under any compulsion to act, with equity to both, as determined
          by the Board in good faith; provided, however, that if the holder of a
          Warrant shall dispute the Fair Market Value as determined by the
          Board, such holder may undertake to have it and the Company retain an
          Independent Expert. The determination of Fair Market Value by the
          Independent Expert shall be final, binding and conclusive on the
          Company and such holder. All costs and expenses of the Independent
          Expert shall be borne by such holder unless the Fair Market Value as
          determined by the Independent Expert exceeds the Fair Market Value as
          determined by the Board by 5% but less than 10%, in which case the
          cost of the Independent Expert shall be shared equally by such holder
          and the Company, and unless the Fair Market Value as determined by the
          Independent Expert exceeds the Fair Market Value as determined by the
          Board by 10% or more, in which case the cost of the Independent Expert
          shall be borne solely by the Company.

               (3) Independent Expert. Independent Expert means a nationally
          recognized investment banking firm reasonably acceptable to the
          Company and the holder of this Warrant who does not (and whose
          affiliates do not) have a financial interest in the Company, any
          holder or any of their affiliates. For purposes of this Section
          10(f)(3), an "affiliate" shall mean any such firm in which the Company
          or any holder owns or controls, directly or indirectly, a voting
          interest greater than 10% of the outstanding voting securities of such
          firm, or a firm which owns or controls, directly or indirectly, a
          voting interest greater than 10% of the outstanding voting securities
          of the Company or any holder.

          (g)  Consideration Received.

               For purposes of any computations respecting consideration
received pursuant to subsections (d) and (e) of this Section 10, the following
shall apply:

                                       11
<PAGE>   15
               (1) in the case of the issuance of shares of Common Stock for
          cash, the consideration shall be the amount of such cash, provided
          that in no case shall any deduction be made for any commissions,
          discounts or other expenses incurred by the Company for any
          underwriting of the issue or otherwise in connection therewith;

               (2) in the case of the issuance of shares of Common Stock for a
          consideration in whole or in part other than cash, the consideration
          other than cash shall be deemed to be the fair market value thereof as
          determined in good faith by the Board (irrespective of the accounting
          treatment thereof), whose determination shall be conclusive, and
          described in a Board resolution; and

               (3) in the case of the issuance of securities convertible into or
          exchangeable for Common Stock, the aggregate consideration received
          therefore shall be deemed to be the consideration received by the
          Company for the issuance of such securities plus the additional
          minimum cash consideration, if any, to be received by the Company upon
          the conversion or exchange thereof (the consideration in each case to
          be determined in the same manner as provided in clauses (1) and (2) of
          this subsection).

          (h)   When De Minimis Adjustment May Be Deferred.

               No adjustment in the Exercise Price need be made unless the
adjustment would require an increase or decrease of at least 1% in the Exercise
Price. Any adjustments that are not made shall be carried forward and taken into
account in any subsequent adjustment.

               All calculations under this Section shall be made to the nearest
cent or to the nearest 1/100th of a share, as the case may be.

           (i) When No Adjustment Required.

               No adjustment need be made for rights to purchase Common Stock
pursuant to a Company plan for reinvestment of dividends or interest.

               No adjustment need be made for a change in the par value or no
par value of the Common Stock.

               To the extent Warrants become convertible into cash, no
adjustment need be made thereafter as to the cash. Interest will not accrue on
the cash.

           (j) Notice of Adjustment.

               Whenever the Exercise Price is adjusted, the Company shall
provide the notices required by Section 14 hereof.

                                       12
<PAGE>   16
           (k) Voluntary Reduction.

               The Company from time to time may reduce the Exercise Price by
any amount for any period of time if the period is at least 20 days and if the
reduction is irrevocable during the period; provided, however, that in no event
may the Exercise Price be less than the par value of a share of Common Stock.

               Whenever the Exercise Price is reduced, the Company shall mail to
Warrant holders a notice of the reduction. The Company shall mail the notice at
least 15 days before the date the reduced Exercise Price takes effect. The
notice shall state the reduced Exercise Price and the period it will be in
effect.

               A reduction of the Exercise Price does not change or adjust the
Exercise Price otherwise in effect for purposes of subsections (a), (b), (c),
(d) and (e) of this Section 10.

          (l)  Reorganization of Company.

               If any reclassification of the Common Stock of the Company or any
consolidation or merger of the Company with another entity, or the sale or lease
of all or substantially all of the Company's assets to another entity shall be
effected in such a way that holders of the Common Stock of the Company shall be
entitled to receive stock, securities or assets with respect to or in exchange
for such Common Stock, then, as a condition precedent to such reclassification,
consolidation, merger, sale or lease, lawful and adequate provisions shall be
made whereby the Warrant holder shall thereafter have the right to purchase and
receive upon the basis and the terms and conditions specified in this Agreement
and in lieu of the shares of Common Stock immediately theretofore purchasable
and receivable upon the exercise of the rights represented hereby, such shares
of stock, securities or assets as may be issued or payable in such
reclassification, consolidation, merger, sale or lease with respect to or in
exchange for the number of shares of Common Stock purchasable and receivable
upon the exercise of the rights represented hereby had such rights been
exercised immediately prior thereto, and in any such case appropriate provision
shall be made with respect to the rights and interests of the holders of the
Warrants to the end that the provisions hereof (including without limitation
provisions for adjustments of the Exercise Price and of the number of shares of
Common Stock purchasable and receivable upon the exercise of the Warrant) shall
thereafter be applicable, as nearly as may be, in relation to any shares of
stock, securities or assets thereafter deliverable upon the exercise hereof. The
Company will not effect any such reclassification, consolidation, merger, sale
or lease, unless prior to the consummation thereof the successor corporation (if
other than the Company) resulting from such reclassification, consolidation or
merger or the corporation purchasing or leasing such assets shall assume by a
supplemental Warrant Agreement, executed and mailed or delivered to the holders
of the Warrants at the last address thereof appearing on the books of Company,
the obligation to deliver to such holders such shares of stock, securities or
assets as, in accordance with the foregoing provisions, such holders may be
entitled to purchase.

                                       13
<PAGE>   17
               If the issuer of securities deliverable upon exercise of Warrants
under the supplemental Warrant Agreement is an affiliate of the formed,
surviving, transferee or lessee corporation, that issuer shall join in the
supplemental Warrant Agreement.

               If this subsection (1) applies, subsections (a), (b), (c), (d)
       and (e) of this Section 10 do not apply.

           (m) When Issuance or Payment May Be Deferred.

               In any case in which this Section 10 shall require that an
adjustment in the Exercise Price be made effective as of a record date for a
specified event, the Company may elect to defer until the occurrence of such
event (i) issuing to the holder of any Warrant exercised after such record date
the Warrant Shares and other capital stock of the Company, if any, issuable upon
such exercise over and above the Warrant Shares and other capital stock of the
Company, if any, issuable upon such exercise on the basis of the Exercise Price
and (ii) paying to such holder any amount in cash in lieu of a fractional share
pursuant to Section 11; provided, however, that the Company shall deliver to
such holder a due bill or other appropriate instrument evidencing such holder's
right to receive such additional Warrant Shares, other capital stock and cash
upon the occurrence of the event requiring such adjustment.

            (n) Adjustment in Number of Shares.

               Upon each adjustment of the Exercise Price pursuant to this
Section 10, each Warrant outstanding prior to the making of the adjustment in
the Exercise Price shall thereafter evidence the right to receive upon payment
of the adjusted Exercise Price that number of shares of Common Stock (calculated
to the nearest hundredth) obtained from the following formula:

                                       E
                        N'  =  N  x   --
                                       E'
where:

                      N'=     the adjusted number of Warrant Shares issuable
                              upon exercise of a Warrant by payment of the
                              adjusted Exercise Price.

                      N=      the number of Warrant Shares previously issuable
                              upon exercise of a Warrant by payment of the
                              adjusted Exercise Price.

                      E'=     the adjusted Exercise Price.

                      E=      the Exercise Price prior to adjustment.

                                       14
<PAGE>   18
           (o) Form of Warrants.

               Irrespective of any adjustments in the Exercise Price or the
number or kind of shares purchasable upon the exercise of the Warrants, Warrants
theretofore or thereafter issued may continue to express the same price and
number and kind of shares as are stated in the Warrants initially issuable
pursuant to this Agreement.

               SECTION 11. Fractional Interests. The Company shall not be
required to issue fractional Warrant Shares on the exercise of Warrants. If more
than one Warrant shall be presented for exercise in full at the same time by the
same holder, the number of full Warrant Shares which shall be issuable upon the
exercise thereof shall be computed on the basis of the aggregate number of
Warrant Shares purchasable on exercise of the Warrants so presented. If any
fraction of a Warrant Share would, except for the provisions of this Section 11,
be issuable on the exercise of any Warrants (or specified portion thereof), the
number of Warrant Shares which shall be issued by the Company on exercise of
such Warrants shall be rounded (i) to the last previous whole number if the
fraction is less than 0.5 of a Warrant Share or (ii) to the next higher whole
number if the fraction is greater than or equal to 0.5 of a Warrant Share.

               SECTION 12. Representations and Warranties of the Company. The
Company represents and warrants to each of the Banks, as of the date hereof, as
follows:

           (a) Corporate Organization.

               The Company is duly organized, validly existing and in good
standing under the laws of the state of its formation. The Company is also duly
authorized, qualified and licensed in all applicable jurisdictions, and under
all applicable laws, regulations, ordinances or orders of public authorities, to
carry on its business in the locations and in the manner presently conducted, to
the extent that the failure to do so would not reasonably be expected to
materially adversely affect the consolidated financial condition or operations
of the Company and could not reasonably be expected to have a material adverse
effect on the Company's ability to perform its obligations under the Restructure
Loan Documents (as defined in the Loan Restructure Agreement), having regard for
its other financial obligations.

            (b) Authorization.

               The execution, delivery and performance by the Company of this
Agreement and the Registration Rights Agreement of even date hereof between the
parties hereto (the "Registration Rights Agreement," and, together with this
Agreement, the "Warrant Documents"), and the issuance by the Company of the
Warrants, are within the Company's corporate powers, have been duly authorized
by all necessary corporate action and do not contravene (i) the Company's
certificate of incorporation, bylaws or other organizational documents or (ii)
any law or regulation or any contractual restriction binding on or affecting the
Company.

                                       15
<PAGE>   19
           (c) Governmental Consents.

               No authorization or approval or other action by, and no notice to
or filing with, any governmental authority or regulatory body (except routine
reports required pursuant to the Securities Exchange Act of 1934, as amended (if
such act is applicable to the Company), which reports will be made in the
ordinary course of business) is required for the due execution, delivery and
performance by the Company of the Warrant Documents or for the issuance by the
Company of the Warrants or the Warrant Shares.

           (d) Validity.

               The Warrant Documents are the binding obligations of the Company,
enforceable in accordance with their respective terms and when executed and
delivered by the Company in accordance with the terms hereof, the Warrants will
constitute a legally valid and binding obligation of the Company; except in each
case as such enforceability may be limited by bankruptcy, insolvency,
reorganization, liquidation, moratorium or other similar laws of general
application and equitable principles relating to or affecting creditors' rights.

          (e) Not an Investment Company.

               The Company is not an "investment company" within the meaning of
the Investment Company Act of 1940, as amended.

          (f) Reports.

               The Company has filed all required forms, reports and documents
with the Securities and Exchange Commission (the "SEC") since January 1, 1997
(collectively, the "SEC Reports"), all of which have complied in all material
respects with all applicable requirements of the Securities Act of 1933, as
amended (the "Securities Act") and the Exchange Act. Except as set forth in
subsequent filings with the SEC, none of the SEC Reports, including without
limitation any financial statements or schedules including therein, contained
any untrue statement of a material fact or omitted to state a material fact
required to be stated therein or necessary in order to make the statements
therein not misleading. Each of the balance sheets (including the related notes)
included in the SEC Reports fairly presents the consolidated financial position
of the Company and its consolidated subsidiaries as of the respective dates
thereof, and the other related statements (including the related notes) included
therein fairly present the results of operations and the changes in financial
position of the Company and its consolidated subsidiaries for the respective
fiscal years, except, in the case of interim financial statements, for year-end
audit adjustments, consisting only of normal recurring accruals. Each of the
financial statements (including the related notes) included in the SEC Reports
has been prepared in accordance with generally accepted accounting principles
consistently applied during the periods involved, except as otherwise noted
therein.

                                       16
<PAGE>   20
           (g) Authorized Shares.

               As of May 10, 2000, (i) the Company has 151,000,000 authorized
shares of capital stock, of which 66,054,041 shares of Common Stock and no
shares of Preferred Stock are issued and outstanding, (ii) the Company has
83,945,959 authorized but unissued shares of Common Stock which will be required
to be issued to satisfy conversions or exercises of the Warrants, (iii) the
Series A Warrants are exercisable into a number of shares of Common Stock equal
to, in the aggregate, 2.5% of the issued and outstanding Common Stock, and (iv)
the Series B Warrants are exercisable into a number of shares of Common Stock
equal to, in the aggregate, 1% of the issued and outstanding Common Stock.

          (h) Status of the Warrants and the Warrant Shares.

               Upon issuance hereunder, the Warrants will be validly issued and
outstanding, fully paid and nonassessable, and the issuance thereof is not
subject to preemptive rights of any other stockholder of the Company. The
Warrant Shares will be duly authorized by all necessary corporate action on the
part of the Company (no consent or approval of stockholders being required by
law, the corporate documents of the Company, the qualification criteria of any
securities exchange or market or otherwise), and upon issuance in accordance
with the terms of this Agreement, will be validly issued and outstanding, fully
paid and nonassessable, and the issuance thereof is not subject to preemptive
rights of any other stockholder of the Company. The Warrant Shares have been
validly reserved for issuance upon the exercise of the Warrants.

               SECTION 13. Purchase for Investment; Authority; Binding
Agreement. Each of the Banks represents and warrants to the Company that:

               (a) such Bank is an Accredited Investor within the meaning of
Rule 501(a) under the Securities Act and the Warrants to be acquired by it
pursuant to this Agreement are being acquired for its own account for investment
and without intent to resell, and such Bank will not offer, sell, transfer,
pledge, hypothecate or otherwise dispose of any of such Warrants, unless
pursuant to a transaction either registered under, or exempt from registration
under, the Securities Act;

               (b) the execution, delivery and performance of each of the
Warrant Documents and the receipt of the Warrants pursuant hereto are within
such Bank's corporate powers and has been duly and validly authorized by all
requisite corporate action;

               (c) each of the Warrant Documents has been duly executed and
delivered by such Bank;

               (d) each of the Warrant Documents constitutes a legally valid and
binding agreement of such Bank; and

                                       17
<PAGE>   21
               (e) such Bank has knowledge and experience in financial and
business matters so as to be capable of evaluating the merits and risks of its
investments in the Warrants and such Bank is capable of bearing the economic
risks of such investments.

               SECTION 14. Notices to Warrant Holders. Upon any adjustment of
the Exercise Price pursuant to Section 10, the Company shall promptly thereafter
(i) cause the Company's Chief Financial Officer to execute a certificate setting
forth the Exercise Price after such adjustment and setting forth in reasonable
detail the method of calculation and the facts upon which such calculations are
based and setting forth the number of Warrant Shares (or portion thereof)
issuable after such adjustment in the Exercise Price, upon exercise of a Warrant
and payment of the adjusted Exercise Price, and (ii) cause to be given to each
of the registered holders of the Warrant Certificates at his address appearing
on the Warrant register written notice of such adjustments by first-class mail,
postage prepaid. Where appropriate, such notice may be given in advance and
included as a part of the notice required to be mailed under the other
provisions of this Section 14.

          In case:

               (a) the Company shall authorize the issuance to all holders of
shares of Common Stock of rights, options or warrants to subscribe for or
purchase shares off Common Stock or of any other subscription rights or
warrants; or

               (b) the Company shall authorize the distribution to all holders
of shares of Common Stock of evidences of its indebtedness or assets (other than
cash dividends or cash distributions payable out of earnings or earned surplus
or dividends or distributions payable in shares of Common Stock); or

               (c) of any consolidation or merger to which the Company is a
party and for which approval of any shareholders of the Company is required, or
of the conveyance or transfer of all or substantially all of the properties and
assets of the Company, or of any reclassification or change of Common Stock
issuable upon exercise of the Warrants (other than a change in par value, or
from par value to no par value, or from no par value to par value, or as a
result of a subdivision or combination), or a tender offer or exchange offer for
shares of Common Stock; or

               (d) of the voluntary or involuntary dissolution, liquidation or
winding up of the Company; or

               (e) the Company proposes to take any action that would require an
adjustment in the Exercise Price pursuant to subsections (a), (b), (c), (d) or
(e) of Section 10, or if the Company takes any action that would require a
supplemental Warrant Agreement pursuant to subsection (1) of Section 10.

then the Company shall cause to be given to each of the registered holders of
the Warrant Certificates at his address appearing on the Warrant register, at
least 20 days (or 10 days in any case specified in clauses (a), (b) or (c)
above) prior to the applicable record date hereinafter

                                       18
<PAGE>   22
specified, or promptly in the case of events for which there is no record date,
by first-class mail, postage prepaid, a written notice stating (i) the date as
of which the holders of record of shares of Common Stock to be entitled to
receive any such rights, options, warrants or distribution are to be determined,
or (ii) the initial expiration date set forth in any tender offer or exchange
offer for shares of Common Stock, or (iii) the date on which any such
consolidation, merger, conveyance, transfer, dissolution, liquidation or winding
up is expected to become effective or consummated, and the date as of which it
is expected that holders of record of shares of Common Stock shall be entitled
to exchange such shares for securities or other property, if any, deliverable
upon such reclassification, consolidation, merger, conveyance, transfer,
dissolution, liquidation or winding up. The failure to give the notice required
by this Section 14 or any defect therein shall not affect the legality or
validity of any distribution, right, option, warrant, consolidation, merger,
conveyance, transfer, dissolution, liquidation or winding up, or the vote upon
any action.

               Nothing contained in this Agreement or in any of the Warrants
shall be construed as conferring upon the holders thereof the right to vote or
to consent or to receive notice as shareholders in respect of the meetings of
shareholders or the election of Directors of the Company or any other matter, or
any rights whatsoever as shareholders of the Company.

               SECTION 15. Notices to Company and Warrant Holder. Any notice or
demand authorized by this Agreement to be given or made by the registered holder
of any Warrant Certificate to or on the Company shall be sufficiently given or
made when and if deposited in the mail, first class or registered, postage
prepaid, addressed to the office of the Company expressly designated by the
Company at its office for purposes of this Agreement (until the Warrant holders
are otherwise notified in accordance with this Section by the Company), as
follows:

                       Komag, Incorporated
                       1710 Automation Parkway
                       San Jose, California 95131-1873
                       Facsimile:  408-944-9234
                       Attn:  Chief Financial Officer

               Any notice pursuant to this Agreement to be given by the Company
to the registered holder(s) of any Warrant Certificate shall be sufficiently
given when and if deposited in the mail, first-class or registered, postage
prepaid, addressed (until the Company is otherwise notified in accordance with
this Section by such holder) to such holder at the address appearing on the
Warrant register of the Company.

               SECTION 16. Supplements and Amendments. The Company may not
supplement or amend this Agreement without the prior written approval of the
holders of Warrants representing at least 51% of the aggregate outstanding
Warrants affected by such supplement or amendment; provided however, that
without the written approval of the holders of all Warrants affected by such
supplement or amendment, no supplement or amendment shall do any of the
following:

               (a) reduce the number of Warrant Shares for which the Warrants
may be exercised;

                                       19
<PAGE>   23
               (b) amend the provisions of Section 10 of this Agreement;

               (c) except as expressly provided in Section 10(a)(3) of this
Agreement, increase the Exercise Price applicable to the Warrants;

               (d) reduce the duration of the Warrants;

               (e) extend the issuance date of the Series B Warrants; or

               (f) amend the provisions of this Section 16.

               SECTION 17. Successors. All the covenants and provisions of this
Agreement by or for the benefit of the Company shall bind and inure to the
benefit of its respective successors and assigns hereunder.

               SECTION 18. Governing Law. This Agreement and each Warrant
Certificate issued hereunder shall be deemed to be a contract made under the
laws of the State of California and for all purposes shall be construed in
accordance with the internal laws of said State.

               SECTION 19. Benefits of This Agreement. Nothing in this Agreement
shall be construed to give to any person or corporation other than the Company
and the registered holders of the Warrant Certificates any legal or equitable
right, remedy or claim under this Agreement; but this Agreement shall be for the
sole and exclusive benefit of the Company and the registered holders of the
Warrant Certificates.

               SECTION 20. Counterparts. This Agreement may be executed in any
number of counterparts and each of such counterparts shall for all purposes be
deemed to be an original, and all such counterparts shall together constitute
but one and the same instrument.

                            [Signature Pages Follow]

                                       20
<PAGE>   24
               IN WITNESS WHEREOF, the parties hereto have caused this Agreement
to be duly executed, as of the day and year first above written.

KOMAG, INCORPORATED

By:
   ----------------------------
Title:
      -------------------------

Address:
1710 Automation Parkway
San Jose, California 95131-1873
Facsimile: (408) 944-9234
Attention:  Chief Financial Officer

FLEET NATIONAL BANK f/k/a BANKBOSTON, N.A.,
as Restructure Agent and as a Restructure Lender

By:
   ----------------------------
Title:
      -------------------------

Address:
100 Federal Street,
Mail Stop 01-06-01
Boston, MA 02110
Facsimile:  (617) 434-4775
Attention:  Donald Sheehan

BANK OF MONTREAL,
as a Restructure Lender

By:
   ----------------------------
Title:
      -------------------------

                                      S-1
<PAGE>   25
Address:
115 S. LaSalle Street, 12 West
Chicago, IL 60603
Facsimile:  (312) 750-6057
Attention:  Jack J. Kane

BEAR, STEARNS & CO. INC.,
as a Restructure Lender

By:
   ----------------------------
Title:
      -------------------------

Address:
245 Park Avenue
New York, New York  10167
Facsimile:  (212) 272-8102
Attention:

COMERICA BANK - CALIFORNIA,
as a Restructure Lender

By:
   ----------------------------
Title:
      -------------------------

Address:
55 Almaden Boulevard
Mail Code: 4041
San Jose, California  95113
Facsimile: (408) 556-5855
Attention:  Carol A. Palestro

OLYMPUS SECURITIES, LTD.,
as a Restructure Lender

By:
   ----------------------------
Title:
      -------------------------

Address:
c/o Citadel Investment Group, LLC

                                      S-2
<PAGE>   26
225 West Washington Street, 9th Floor
Chicago, Illinois  60606
Facsimile:  (312) 368-4650
Attention:  Bradford Couri

                                      S-3
<PAGE>   27
NELSON PARTNERS LTD.,
as a Restructure Lender

By:
   ----------------------------
Title:
      -------------------------

Address:
c/o Citadel Investment Group, LLC
225 West Washington Street, 9th Floor
Chicago, Illinois  60606
Facsimile:  (312) 368-4650
Attention:  Bradford Couri

THE BANK OF NOVA SCOTIA,
as a Restructure Lender

By:
   ----------------------------
Title:
      -------------------------

Address:
One Liberty Plaza
New York, New York 10006
Facsimile:  (212) 225-5205
Attention:  Norm Gillespie

UNION BANK OF CALIFORNIA, N.A.,
as a Restructure Lender

By:
   ----------------------------
Title:
      -------------------------

Address:
350 California Street, 7th Floor
San Francisco, California  94104
Facsimile:  (415) 705-7390
Attention:  Christiana Creekpaum

                                      S-4
<PAGE>   28
LOEB PARTNERS CORPORATION,
as a Restructure Lender

By:
   ----------------------------
Title:
      -------------------------

Address:
61 Broadway, 24th Floor
New York, New York  10006
Facsimile:  (212) 574-2003
Attention:  Robert Grubin

THE DAI-ICHI KANGYO BANK, LIMITED,
as a Restructure Lender

By:
   ----------------------------
Title:
      -------------------------

Address:
Corporate Finance Department I
One World Trade Center, Suite 4911
New York, NY 10048
Facsimile:  (212) 912-1879
Attention:  Nelson Chang

THE INDUSTRIAL BANK OF JAPAN, LIMITED,
as a Restructure Lender

By:
   ----------------------------
Title:
      -------------------------

Address:
One Market Street
Spear Tower, Suite 1610
San Francisco, California  94105
Facsimile:  (415) 982-1917
Attention:  Joseph A. Endoso

                                      S-5
<PAGE>   29
THE MITSUBISHI TRUST AND BANKING CORPORATION,
as a Restructure Lender

By:
   ----------------------------
Title:
      -------------------------

Address:
520 Madison Avenue, 26th Floor
New York, New York  10022
Facsimile:  (212) 644-6825
Attention:  Daniel Chang

SANWA BANK CALIFORNIA,
as a Restructure Lender

By:
   ----------------------------
Title:
      -------------------------

Address:
444 Market Street, 22nd Floor
San Francisco, CA 94111
Facsimile:  (415) 597-5491
Attention:  George Vetek

BANK ONE, N.A.,
as a Restructure Lender

By:
   ----------------------------
Title:
      -------------------------

Address:
Bank One, N.A.
Western Region Managed Assets
AZ1-1283
201 N. Central Avenue
Phoenix, AZ 85004-2267
Facsimile:  (602) 221-1737
Attention:  Dennis B. Warren

                                      S-6
<PAGE>   30
THE FUJI BANK, LIMITED,
as a Restructure Lender

By:
   ----------------------------
Title:
      -------------------------

Address:
333 South Hope Street, 39th Floor
Los Angeles, CA 90071
Facsimile:  (213) 253-4178
Attention:

THE SUMITOMO BANK, LIMITED,
as a Restructure Lender

By:
   ----------------------------
Title:
      -------------------------

Address:
555 California Street, Suite 3350
San Francisco, California  94104
Facsimile:  (415) 362-6527
Attention:  Azar Shakeri

                                      S-7
<PAGE>   31
                                   SCHEDULE 1
<TABLE>
<CAPTION>
BANK                                            WARRANT SHARES        WARRANT SHARES
----                                            --------------        --------------
                                                SERIES A              SERIES B
                                                --------              --------
<S>                                              <C>                  <C>
Fleet National Bank f/k/a/ BankBoston, N.A       214,131              85,652
Bank of Montreal                                  54,440              21,776
Bear, Stearns & Co. Inc.                          22,230               8,892
Comerica Bank - California                        90,734              36,293
Olympus Securities, Ltd.                          53,987              21,595
Nelson Partners Ltd.                              35,386              14,154
The Bank of Nova Scotia                           72,587              29,035
Loeb Partners Corporation                         19,054               7,622
Union Bank of California, N.A                     72,587              29,035
The Dai-Ichi Kangyo Bank, Limited                222,297              88,919
The Industrial Bank of Japan, Limited             95,270              38,108
The Mitsubishi Trust and Banking Corporation      63,514              25,405
Sanwa Bank California                             63,513              25,405
Bank One, N.A                                     95,270              38,108
The Industrial Bank of Japan, Limited            158,784              63,514
The Mitsubishi Trust and Banking Corporation     127,027              50,811
The Fuji Bank, Limited                            95,270              38,108
The Sumitomo Bank, Limited                        95,270              38,108
                                              ----------            --------
                                               1,651,351             660,540
</TABLE>

                                   Schedule-1
<PAGE>   32
                                                                       EXHIBIT A

                          [Form of Warrant Certificate]

THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN REGISTERED UNDER
THE SECURITIES ACT OF 1933 OR THE SECURITIES LAWS OF ANY STATE AND MAY NOT BE
SOLD OR OTHERWISE DISPOSED OF EXCEPT PURSUANT TO AN EFFECTIVE REGISTRATION
STATEMENT UNDER SUCH ACT AND APPLICABLE STATE SECURITIES LAWS OR AN APPLICABLE
EXEMPTION TO THE REGISTRATION REQUIREMENT OF SUCH ACT OR SUCH LAWS. SUCH SALE OR
OTHER DISPOSITION MUST ALSO BE IN COMPLIANCE WITH THE RESTRICTIONS ON TRANSFER
SET FORTH IN THE WARRANT AGREEMENT DATED AS OF JUNE 1, 2000, A COPY OF WHICH MAY
BE OBTAINED FROM KOMAG, INCORPORATED AT ITS PRINCIPAL EXECUTIVE OFFICE.

                     EXERCISABLE ON OR AFTER THE DATE HEREOF
                          AND ON OR BEFORE JUNE 1, 2010

No.                                                       ___ Series A Warrants
                          Series A Warrant Certificate

                               KOMAG, INCORPORATED

               This Warrant Certificate certifies that _________________, or
registered assigns, is the registered holder of ___ Series A Warrants expiring
June 1, 2010 (the "Warrants") to purchase Common Stock, $0.01 par value (the
"Common Stock"), of Komag, Incorporated, a Delaware corporation (the "Company").
Each Series A Warrant entitles the holder upon exercise on or after the date
hereof to receive from the Company on or before 5:00 p.m., Los Angeles time, on
June 1, 2010, one fully paid and nonassessable share of Common Stock (a "Warrant
Share") at the initial exercise price (the "Exercise Price") of $_______ payable
as otherwise provided in the Warrant Agreement referred to below, upon surrender
of this Warrant Certificate and payment of the Exercise Price at the office of
the Company designated for such purpose, but only subject to the conditions set
forth herein and in the Warrant Agreement. The Exercise Price and number of
Warrant Shares issuable upon exercise of the Warrants are subject to adjustment
upon the occurrence of certain events set forth in the Warrant Agreement.

               No Warrant may be exercised after 5:00 p.m., Los Angeles time, on
June 1, 2010, and to the extent not exercised by such time such Warrants shall
become void.

               The Series A Warrants evidenced by this Warrant Certificate are
part of a duly authorized issue of Warrants expiring June 1, 2010 entitling the
holder on exercise to receive shares of Common Stock of the Company, and are
issued pursuant to a Warrant Agreement dated as of the date hereof (the "Warrant
Agreement"), duly executed and delivered by the Company, which Warrant Agreement
is hereby incorporated by reference in and made a part of this instrument and is
hereby referred to for a description of the rights, limitation of rights,
obligations, duties and immunities thereunder of the Company and the holders
(the words "holders" or "holder"

                                      A-1
<PAGE>   33
meaning the registered holders or registered holder) of the Warrants. A copy of
the Warrant Agreement may be obtained by the holder hereof upon written request
to the Company.

               Warrants may be exercised at any time on or before June 1, 2010.
The holder of Warrants evidenced by this Warrant Certificate may exercise them
by surrendering this Warrant Certificate, with the form of election to purchase
set forth hereon properly completed and executed, together with payment of the
Exercise Price at the office of the Company designated for such purpose. In the
event that upon any exercise of Warrants evidenced hereby the number of Warrants
exercised shall be less than the total number of Warrants evidenced hereby,
there shall be issued to the holder hereof or his assignee a new Warrant
Certificate evidencing the number of Warrants not exercised. No adjustment shall
be made for any dividends on any Common Stock issuable upon exercise of this
Warrant.

               The Warrant Agreement provides that upon the occurrence of
certain events the Exercise Price set forth on the face hereof may, subject to
certain conditions, be adjusted. If the Exercise Price is adjusted, the Warrant
Agreement provides that the number of shares of Common Stock issuable upon the
exercise of each Warrant shall be adjusted. No fractions of a share of Common
Stock will be issued upon the exercise of any Warrant, but the Company will pay
the cash value thereof determined as provided in the Warrant Agreement.

               The holders of the Warrants are entitled to certain registration
rights with respect to the Common Stock purchasable upon exercise thereof. Said
registration rights are set forth in full in the Registration Rights Agreement
dated as of the date hereof, between the Company and the Banks identified in the
Warrant Agreement. A copy of the Registration Rights Agreement may be obtained
by the holder hereof upon written request to the Company.

               Warrant Certificates, when surrendered at the office of the
Company by the registered holder thereof in person or by legal representative or
attorney duly authorized in writing, may be exchanged, in the manner and subject
to the limitations provided in the Warrant Agreement, but without payment of any
service charge, for another Warrant Certificate or Warrant Certificates of like
tenor evidencing in the aggregate a like number of Warrants.

               Upon due presentation for registration of transfer of this
Warrant Certificate at the office of the Company, a new Warrant Certificate or
Warrant Certificates of like tenor and evidencing in the aggregate a like number
of Warrants shall be issued to the transferee(s) in exchange for this Warrant
Certificate, subject to the limitations provided in the Warrant Agreement,
without charge except for any tax or other governmental charge imposed in
connection therewith.

               The Company may deem to treat the registered holder(s) thereof as
the absolute owner(s) of this Warrant Certificate (notwithstanding any notation
of ownership or other writing hereon made by anyone), for the purpose of any
exercise hereof, of any distribution to the holder(s) hereof, and for all other
purposes, and the Company shall not be affected by any notice to the contrary.
Neither the Warrants nor this Warrant Certificate entitles any holder hereof to
any rights of a stockholder of the Company.

                                      A-2

<PAGE>   34

               This Warrant Certificate shall not be valid unless countersigned
by the Company, as such term is used in the Warrant Agreement.

               IN WITNESS WHEREOF, the Company has caused this Warrant
certificate to be signed by its President and by its Secretary and has caused
its corporate seal to be affixed hereunto or imprinted hereon.

                                      KOMAG, INCORPORATED,
                                      a Delaware corporation

                                      By:
                                         ---------------------------------------
                                      Name:   Thian Hoo Tan
                                      Title:  President

                                      By:
                                         ---------------------------------------
                                      Name:  Edward H. Siegler
                                      Title:  Secretary

                                      A-3
<PAGE>   35
                               [Form of Election]

                    (To Be Executed Upon Exercise of Warrant)

               The undersigned hereby irrevocably elects to exercise the right,
represented by this Warrant Certificate, to receive _________ shares of Common
Stock and herewith tenders payment for such shares to the order of Komag,
Incorporated in the amount of $________ as follows: (check applicable box)

               [ ]    in the form of cash or in immediately available funds
                      payable to the order of the Company

              *[ ]    in lieu of cash, net shares of Common Stock calculated
                      as follows:

               Current Market Price - Exercise Price
               -------------------------------------- x Warrant Shares Exercised
                        Current Market Price

               The undersigned requests that a certificate for such shares be
registered in the name of ________________, whose address is
____________________________ and that such shares be delivered to
________________ whose address is ________________________. If said number of
shares is less than all of the shares of Common Stock purchasable hereunder, the
undersigned requests that a new Warrant Certificate representing the remaining
balance of such shares be registered in the name of _____________, whose address
is ___________________________, and that such Warrant Certificate be delivered
to _________________, whose address is _____________________.

                                     Signature:
                                               ---------------------------------

Date:

                                     Signature Guaranteed:
                                                          ----------------------

* Please note that this is the only form of payment available if this Warrant
Certificate is to be exercised within two years of its issuance.

                                      A-4
<PAGE>   36
                              [Form of Assignment]

                   (To Be Executed Upon Assignment of Warrant)

               If you, the holder, want to assign this Warrant, fill in the form
below and have your signature guaranteed:

               For value received, I or we assign and transfer this Warrant to:

--------------------------------------------------------------------------------
                      (INSERT ASSIGNEE'S SOCIAL SECURITY OR
                           TAX IDENTIFICATION NUMBER)

          -----------------------------------------------------------

          -----------------------------------------------------------

--------------------------------------------------------------------------------

--------------------------------------------------------------------------------

--------------------------------------------------------------------------------
              (Print or type assignee's name, address and zip code)

and appoints ______________________________________ agent to transfer this
security on the books of the Company. The agent may substitute another to act
for him.

               In connection with the transfer of this Warrant, the undersigned
certifies that:

               (Check one)

                 [ ] This Warrant is being transferred to Komag, Incorporated.

                 [ ] This Warrant is being transferred to a person or entity
                     other than Komag, Incorporated, in connection with which
                     the Company has received an opinion of counsel
                     (satisfactory to it in form and substance) to the effect
                     that the transfer is being made pursuant to an exemption
                     from, or in a transaction not subject to, the registration
                     requirements of the Securities Act.

Date:
     ---------------------------------------------------------------------------

Your signature:
               -----------------------------------------------------------------
               (Sign exactly as your name appears on this Warrant)

Signature Guaranteed by *:
                          ------------------------------------------------------

* Signature must be guaranteed by an eligible guarantor institution within the
meaning of Securities and Exchange Commission Rule 17Ad-15 (including banks,
stock brokers, savings and loan associations, national securities exchanges,
registered securities associations, clearing agencies and credit unions) with
membership or participation in the Securities Transfer Agents Medallion Program
("STAMP") or such other signature guarantee medallion program as may be approved
by the Registrar in addition to, or substitution for, STAMP, if this Security is
to be delivered other than to and in the name of the registered holder.

IF NONE OF THE FOREGOING BOXES IS CHECKED, THE TRUSTEE SHALL NOT BE OBLIGATED TO
REGISTER THE TRANSFER OF THIS SECURITY UNLESS AND UNTIL THE CONDITIONS TO ANY
SUCH TRANSFER OF REGISTRATION SET FORTH HEREIN, ON THE FACE HEREOF AND IN THE
WARRANT AGREEMENT SHALL HAVE BEEN SATISFIED.

                                      A-5
<PAGE>   37
                                                                       EXHIBIT B

                          [Form of Warrant Certificate]

THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN REGISTERED UNDER
THE SECURITIES ACT OF 1933 OR THE SECURITIES LAWS OF ANY STATE AND MAY NOT BE
SOLD OR OTHERWISE DISPOSED OF EXCEPT PURSUANT TO AN EFFECTIVE REGISTRATION
STATEMENT UNDER SUCH ACT AND APPLICABLE STATE SECURITIES LAWS OR AN APPLICABLE
EXEMPTION TO THE REGISTRATION REQUIREMENT OF SUCH ACT OR SUCH LAWS. SUCH SALE OR
OTHER DISPOSITION MUST ALSO BE IN COMPLIANCE WITH THE RESTRICTIONS ON TRANSFER
SET FORTH IN THE WARRANT AGREEMENT DATED AS OF JUNE 1, 2000, A COPY OF WHICH MAY
BE OBTAINED FROM KOMAG, INCORPORATED AT ITS PRINCIPAL EXECUTIVE OFFICE.

                      EXERCISABLE ON OR AFTER JUNE 1, 2001
                          AND ON OR BEFORE JUNE 1, 2011

No.                                                        ___ Series B Warrants
                          Series B Warrant Certificate

                               KOMAG, INCORPORATED

               This Warrant Certificate certifies that _________________, or
registered assigns, is the registered holder of ___ Series B Warrants expiring
not later than June 1, 2011 (the "Warrants") to purchase Common Stock, $0.01 par
value (the "Common Stock"), of Komag, Incorporated, a Delaware corporation (the
"Company"). Each Series B Warrant entitles the holder upon exercise on or after
June 1, 2001 to receive from the Company on or before 5:00 p.m., Los Angeles
time, on June 1, 2011, unless earlier terminated, one fully paid and
nonassessable share of Common Stock (a "Warrant Share") at the initial exercise
price (the "Exercise Price") of $_______ payable as otherwise provided in the
Warrant Agreement referred to below, upon surrender of this Warrant Certificate
and payment of the Exercise Price at the office of the Company designated for
such purpose, but only subject to the conditions set forth herein and in the
Warrant Agreement. The Exercise Price and number of Warrant Shares issuable upon
exercise of the Warrants are subject to adjustment upon the occurrence of
certain events set forth in the Warrant Agreement.

               Notwithstanding anything to the contrary in this Warrant
Certificate, the Series B Warrants shall become void and all rights thereunder
and all rights in respect thereof under this Warrant Certificate shall cease if
the unpaid loan balances on the notes issued pursuant to the Credit Facilities,
in the aggregate, does not exceed $160 million.

               No Warrant may be exercised after 5:00 p.m., Los Angeles time, on
June 1, 2011, and to the extent not exercised by such time such Warrants shall
become void.

               The Series B Warrants evidenced by this Warrant Certificate are
part of a duly authorized issue of Warrants expiring June 1, 2011 entitling the
holder on exercise to receive shares of Common Stock, $0.01 par value, of the
Company (the "Common Stock"), and are issued

                                      B-1
<PAGE>   38
pursuant to a Warrant Agreement dated as of the date hereof (the "Warrant
Agreement"), duly executed and delivered by the Company, which Warrant Agreement
is hereby incorporated by reference in and made a part of this instrument and is
hereby referred to for a description of the rights, limitation of rights,
obligations, duties and immunities thereunder of the Company and the holders
(the words "holders" or "holder" meaning the registered holders or registered
holder) of the Warrants. A copy of the Warrant Agreement may be obtained by the
holder hereof upon written request to the Company.

               Warrants may be exercised at any time on or after June 1, 2001
and on or before June 1, 2011. The holder of Warrants evidenced by this Warrant
Certificate may exercise them by surrendering this Warrant Certificate, with the
form of election to purchase set forth hereon properly completed and executed,
together with payment of the Exercise Price at the office of the Company
designated for such purpose. In the event that upon any exercise of Warrants
evidenced hereby the number of Warrants exercised shall be less than the total
number of Warrants evidenced hereby, there shall be issued to the holder hereof
or his assignee a new Warrant Certificate evidencing the number of Warrants not
exercised. No adjustment shall be made for any dividends on any Common Stock
issuable upon exercise of this Warrant.

               The Warrant Agreement provides that upon the occurrence of
certain events the Exercise Price set forth on the face hereof may, subject to
certain conditions, be adjusted. If the Exercise Price is adjusted, the Warrant
Agreement provides that the number of shares of Common Stock issuable upon the
exercise of each Warrant shall be adjusted. No fractions of a share of Common
Stock will be issued upon the exercise of any Warrant, but the Company will pay
the cash value thereof determined as provided in the Warrant Agreement.

               The holders of the Warrants are entitled to certain registration
rights with respect to the Common Stock purchasable upon exercise thereof. Said
registration rights are set forth in full in the Registration Rights Agreement
dated as of the date hereof, between the Company and the Banks identified in the
Warrant Agreement. A copy of the Registration Rights Agreement may be obtained
by the holder hereof upon written request to the Company.

               Warrant Certificates, when surrendered at the office of the
Company by the registered holder thereof in person or by legal representative or
attorney duly authorized in writing, may be exchanged, in the manner and subject
to the limitations provided in the Warrant Agreement, but without payment of any
service charge, for another Warrant Certificate or Warrant Certificates of like
tenor evidencing in the aggregate a like number of Warrants.

               Upon due presentation for registration of transfer of this
Warrant Certificate at the office of the Company, a new Warrant Certificate or
Warrant Certificates of like tenor and evidencing in the aggregate a like number
of Warrants shall be issued to the transferee(s) in exchange for this Warrant
Certificate, subject to the limitations provided in the Warrant Agreement,
without charge except for any tax or other governmental charge imposed in
connection therewith.

The Company may deem to treat the registered holder(s) thereof as the absolute
owner(s) of this Warrant Certificate (notwithstanding any notation of ownership
or other writing hereon made by anyone), for the purpose of any exercise hereof,
of any distribution to the holder(s)

                                      B-2
<PAGE>   39
hereof, and for all other purposes, and the Company shall not be affected by any
notice to the contrary. Neither the Warrants nor this Warrant Certificate
entitles any holder hereof to any rights of a stockholder of the Company.

               This Warrant Certificate shall not be valid unless countersigned
by the Company, as such term is used in the Warrant Agreement.

               IN WITNESS WHEREOF, the Company has caused this Warrant
certificate to be signed by its President and by its Secretary and has caused
its corporate seal to be affixed hereunto or imprinted hereon.

                                       KOMAG, INCORPORATED,
                                       a Delaware corporation

                                       By:
                                          --------------------------------------
                                       Name:   Thian Hoo Tan
                                       Title:  President

                                       By:
                                          --------------------------------------
                                       Name:  Edward H. Siegler
                                       Title:  Secretary

                                      B-3
<PAGE>   40
                               [Form of Election]

                    (To Be Executed Upon Exercise of Warrant)

               The undersigned hereby irrevocably elects to exercise the right,
represented by this Warrant Certificate, to receive _________ shares of Common
Stock and herewith tenders payment for such shares to the order of Komag,
Incorporated in the amount of $________ as follows: (check applicable box)

               [ ]  in the form of cash or in immediately available funds
                    payable to the order of the Company

              *[ ]  in lieu of cash, net shares of Common Stock calculated as
                    follows:

                Current Market Price - Exercise Price
                -------------------------------------x  Warrant Shares Exercised
                        Current Market Price

               The undersigned requests that a certificate for such shares be
registered in the name of ________________, whose address is
____________________________ and that such shares be delivered to
________________ whose address is ________________________. If said number of
shares is less than all of the shares of Common Stock purchasable hereunder, the
undersigned requests that a new Warrant Certificate representing the remaining
balance of such shares be registered in the name of _____________, whose address
is ___________________________, and that such Warrant Certificate be delivered
to _________________, whose address is _____________________.

                                     Signature:
                                               ---------------------------------

Date:

                                     Signature Guaranteed:
                                                          ----------------------

* Please note that this is the only form of payment available if this Warrant
Certificate is to be exercised within two years of its issuance.

                                      B-4
<PAGE>   41
                              [Form of Assignment]

                   (To Be Executed Upon Assignment of Warrant)

               If you, the holder, want to assign this Warrant, fill in the form
below and have your signature guaranteed:

               For value received, I or we assign and transfer this Warrant to:

--------------------------------------------------------------------------------
                      (INSERT ASSIGNEE'S SOCIAL SECURITY OR
                           TAX IDENTIFICATION NUMBER)

       ----------------------------------------------------------------

       ----------------------------------------------------------------

--------------------------------------------------------------------------------

--------------------------------------------------------------------------------

--------------------------------------------------------------------------------
              (Print or type assignee's name, address and zip code)

and appoints __________________________________________ agent to transfer this
security on the books of the Company. The agent may substitute another to act
for him.

               In connection with the transfer of this Warrant, the undersigned
certifies that:

               (Check one)

                    [ ] This Warrant is being transferred to Komag,
                        Incorporated.

                    [ ] This Warrant is being transferred to a person or
                        entity other than Komag, Incorporated, in connection
                        with which the Company has received an opinion of
                        counsel (satisfactory to it in form and substance) to
                        the effect that the transfer is being made pursuant to
                        an exemption from, or in a transaction not subject to,
                        the registration requirements of the Securities Act.

Date:
     ---------------------------------------------------------------------------

Your signature:
               -----------------------------------------------------------------
               (Sign exactly as your name appears on this Warrant)

Signature Guaranteed by *:
                          ------------------------------------------------------

* Signature must be guaranteed by an eligible guarantor institution within the
meaning of Securities and Exchange Commission Rule 17Ad-15 (including banks,
stock brokers, savings and loan associations, national securities exchanges,
registered securities associations, clearing agencies and credit unions) with
membership or participation in the Securities Transfer Agents Medallion Program
("STAMP") or such other signature guarantee medallion program as may be approved
by the Registrar in addition to, or substitution for, STAMP, if this Security is
to be delivered other than to and in the name of the registered holder.

IF NONE OF THE FOREGOING BOXES IS CHECKED, THE TRUSTEE SHALL NOT BE OBLIGATED TO
REGISTER THE TRANSFER OF THIS SECURITY UNLESS AND UNTIL THE CONDITIONS TO ANY
SUCH TRANSFER OF REGISTRATION SET FORTH HEREIN, ON THE FACE HEREOF AND IN THE
WARRANT AGREEMENT SHALL HAVE BEEN SATISFIED.

                                      B-5<PAGE>   1

                                                                  EXECUTION COPY
                                                                     EXHIBIT 4.3
--------------------------------------------------------------------------------

                          REGISTRATION RIGHTS AGREEMENT

                                 BY AND BETWEEN

                               KOMAG, INCORPORATED

                                       AND

                               FLEET NATIONAL BANK
                             F/K/A BANKBOSTON, N.A.

                                BANK OF MONTREAL

                            BEAR, STEARNS & CO. INC.

                           COMERICA BANK - CALIFORNIA

                            OLYMPUS SECURITIES, LTD.

                               NELSON PARTNERS LTD

                             THE BANK OF NOVA SCOTIA

                         UNION BANK OF CALIFORNIA, N.A.

                            LOEB PARTNERS CORPORATION

                        THE DAI-ICHI KANGYO BANK, LIMITED

                      THE INDUSTRIAL BANK OF JAPAN, LIMITED

                  THE MITSUBISHI TRUST AND BANKING CORPORATION

                              SANWA BANK CALIFORNIA

                                 BANK ONE, N.A.

                             THE FUJI BANK, LIMITED

                           THE SUMITOMO BANK, LIMITED

                            DATED AS OF JUNE 1, 2000

--------------------------------------------------------------------------------

<PAGE>   2
                                TABLE OF CONTENTS
<TABLE>
<CAPTION>
<S>                                                                                                                        <C>
SECTION 1. Definitions......................................................................................................1

SECTION 2. Securities Subject to this Agreement.............................................................................2

                             (a) Registrable Securities.....................................................................2
                             (b) Holders of Registrable Securities..........................................................2

SECTION 3. Piggyback Registrations..........................................................................................3

                             (a) Piggyback Registration.....................................................................3
                             (b) Demand Registrations.......................................................................4

SECTION 4. Registration Procedures..........................................................................................5

SECTION 5. Registration Expenses............................................................................................9

SECTION 6. Indemnification.................................................................................................11

                             (a) Indemnification by Company................................................................11
                             (b) Indemnification by Holder of Registrable Securities.......................................12
                             (c) Contribution..............................................................................12

SECTION 7. Rule 144........................................................................................................13

SECTION 8. Participation in Underwritten Registrations.....................................................................13

SECTION 9. Miscellaneous...................................................................................................14

                             (a) Termination...............................................................................14
                             (b) No Inconsistent Agreements................................................................14
                             (c) Adjustments Affecting Registrable Securities..............................................14
                             (d) Amendments and Waivers....................................................................14
                             (e) Notices...................................................................................14
                             (f) Successors and Assigns....................................................................15
                             (g) Counterparts..............................................................................15
                             (h) Headings..................................................................................15
                             (i) Governing Law.............................................................................16
                             (j) Severability..............................................................................16
                             (k) Entire Agreement..........................................................................16
</TABLE>

-----------------------
               This Table of Contents does not constitute a part of this
Agreement or have any bearing upon the interpretation of any of its terms or
provisions.

                                       i
<PAGE>   3

               THIS REGISTRATION RIGHTS AGREEMENT (the "Agreement") is dated as
of June 1, 2000, and entered into by and between Komag, Incorporated, a Delaware
corporation (the "Company"), and Fleet National Bank f/k/a BankBoston, N.A.,
Bank of Montreal, Bear Stearns & Co., Inc., Comerica Bank - California, Olympus
Securities, Ltd., Nelson Partners, Ltd., The Bank of Nova Scotia, Union Bank of
California, N.A., Loeb Partners Corporation, The Dai-Ichi Kangyo Bank, Limited,
The Industrial Bank of Japan, Limited, The Mitsubishi Trust and Banking
Corporation, Sanwa Bank California, Bank One, N.A., The Fuji Bank, Limited, and
The Sumitomo Bank, Limited (collectively, "Banks").

               This Agreement is made pursuant to the Warrant Agreement dated as
of the date hereof, between the Company and Banks (the "Warrant Agreement"). To
induce Banks to enter into the Warrant Agreement, the Company has agreed to
provide the registration rights set forth in this Agreement.

               The parties hereby agree as follows:

               SECTION 1.  Definitions.

               As used in this Agreement, the following capitalized terms shall
have the following meanings:

               Agent: Any Person authorized to act and who acts on behalf of a
Bank with respect to the transactions contemplated by this Agreement.

               Common Stock: The common stock, $0.01 par value per share, of the
Company.

               Exchange Act: The Securities Exchange Act of 1934, as amended
from time to time.

               NASD: National Association of Securities Dealers, Inc.

               Person: An individual, partnership, corporation, limited
liability company, trust or unincorporated organization, or other business
entity, or a government or agency or political subdivision thereof.

               Prospectus: The prospectus included in any Registration
Statement, as amended or supplemented by any prospectus supplement with respect
to the terms of the offering of any portion of the Registrable Securities
covered by the Registration Statement and by all other amendments and
supplements to the prospectus, including post-effective amendments and all
material incorporated by reference in such prospectus.

               Registrable Securities: The Warrant Shares. Registrable
Securities shall also include any securities which may be issued or distributed
with respect to, or in exchange for, such Registrable Securities pursuant to a
stock dividend, stock split or other distribution, merger, consolidation,
recapitalization or reclassification or similar transaction; provided, however,
that any such Registrable Securities shall cease to be Registrable Securities to
the extent (i) a Registration Statement with respect to the sale of such
Registrable Securities has been declared effective under the Securities Act and
such Registrable Securities have been disposed of in

                                       1
<PAGE>   4
accordance with the plan of distribution set forth in such Registration
Statement, (ii) such Registrable Securities are distributed pursuant to Rule 144
(or any similar provision then in force) under the Securities Act, or (iii) such
Registrable Securities shall have been otherwise transferred, new certificates
for them not bearing a legend restricting transfer under the Securities Act
shall have been delivered by the Company and they may be publicly resold without
subsequent registration under the Securities Act or in compliance with Rule 144
thereunder; provided, further, however, that any securities that have ceased to
be Registrable Securities cannot thereafter become Registrable Securities, and
any securities that are issued or distributed in respect of securities that have
ceased to be Registrable Securities are not Registrable Securities.

               Registration: A Piggyback Registration (as defined in Section
3(a)) or Demand Registration (as defined in Section 3(b)) of the Company's
securities for sale to the public under a Registration Statement.

               Registration Expenses:  See Section 6 hereof.

               Registration Statement: Any registration statement of the Company
filed with the Securities and Exchange Commission under the rules and
regulations promulgated under the Securities Act, including the Prospectus,
amendments and supplements to such Registration Statement, including
post-effective amendments, and all exhibits and all material incorporated by
reference in such Registration Statement.

               Securities Act: The Securities Act of 1933, as amended from time
to time.

               SEC:  The Securities and Exchange Commission.

               Underwritten Registration or Underwritten Offering: A
Registration in which securities of the Company are sold to an underwriter for
reoffering to the public.

               Warrants: The Series A Common Stock Purchase Warrants and the
Series B Common Stock Purchase Warrants both to purchase shares of Common Stock,
issued and sold pursuant to the Warrant Agreement.

               Warrant Shares: Any shares of Common Stock issued or issuable
upon exercise of any of the Warrants.

               SECTION 2.  Securities Subject to this Agreement.

                  (a)  Registrable Securities. The securities entitled to the
                       benefits of this Agreement are the Registrable
                       Securities.

                  (b)  Holders of Registrable Securities. Subject to Section
                       10(f), a Person is deemed to be a holder of Registrable
                       Securities whenever such Person owns Registrable
                       Securities or the Warrants.

                                       2
<PAGE>   5
               SECTION 3.  Registrations.

                  (a)  Piggyback Registrations.

               (1) Participation. Subject to Section 3(a)(2) hereof, if at any
time from and after the date hereof the Company proposes to file a Registration
Statement under the Securities Act with respect to any offering of any of its
securities of the same class as the Registrable Securities, whether or not by
the Company for its own account (other than (i) a registration on Form S-4 or
S-8 or any successor form to such Forms, or (ii) any registration of securities
as it relates to an offering and sale by any employee stock plan or other
employee benefit plan arrangement), then, as promptly as practicable, the
Company shall give written notice of such proposed filing to each holder of
Registrable Securities and such notice shall offer the holders of Registrable
Securities the opportunity to register such number of Registrable Securities as
each such holder may request (a "Piggyback Registration"). Subject to Section
3(b), the Company shall include in such Registration Statement all Registrable
Securities requested within 30 days after the receipt of any such notice (which
request shall specify the Registrable Securities intended to be disposed of by
such holder) to be included in the Registration for such offering pursuant to a
Piggyback Registration. Each holder of Registrable Securities shall be permitted
to withdraw all or part of such holder's Registrable Securities from a Piggyback
Registration at any time prior to the earlier of the effective date or any
request for the acceleration of the effective date thereof. The Company shall
keep any Registration Statement filed pursuant to this Section 3(a)(1) current
and effective for a period expiring on the earlier of six months from the
effective date of such Registration Statement or until all of the Registrable
Securities registered pursuant to this Section 3(a) have been sold.
Notwithstanding the foregoing, in the event that, in the good faith judgment of
the Company's Board of Directors, it is advisable to suspend use of the
Prospectus due to impending corporate developments, public filings with the SEC
or similar events, the Company shall deliver promptly a written certificate to
each holder of Registrable Securities and the managing underwriters, if any, to
the effect that the use of the Prospectus is to be suspended until the Company
shall deliver a written notice that the use of the Prospectus may be resumed.
Thereafter, the use of the Prospectus shall be suspended, and the Company shall
not be required to maintain the effectiveness of, or amend or update the
Registration Statement, or amend or supplement the Prospectus; provided,
however, that the Company shall only be permitted to suspend the use of the
Prospectus for a period not to exceed 45 days in any six-month period or two
periods not to exceed an aggregate of 90 days in any 12-month period. The
Company will use its best efforts to ensure that the use of the Prospectus may
be resumed as soon as, in the good faith judgment of the Company's Board of
Directors, disclosure of the material relating to such pending development,
filing or event would not have a materially adverse effect on the Company. If
the Company shall give any suspension notice pursuant to this Section 3(a)(1),
the period contemplated by Section 4(b) hereof shall be extended by the number
of days during such period from and including the date of giving notice to and
including the date of giving such notice to and including the date when each
holder of Registrable Securities shall have received notice that the use of the
Prospectus may be resumed.

                                       3
<PAGE>   6
               (2) Underwriter's Cutback. The Company shall use its best efforts
to cause the managing underwriter or underwriters of a proposed Underwritten
Offering to permit the Registrable Securities requested to be included in the
Registration for such offering under Section 3(a)(1) (the "Piggyback
Securities"), to be included on the same terms and conditions as any similar
securities included therein. Notwithstanding the foregoing, if the managing
underwriter of any such proposed Underwritten Offering determines that marketing
factors require a limitation of the number of securities to be underwritten, the
managing underwriter may limit or exclude the amount of Registrable Securities
to be included in the registration and underwriting as follows: the Company will
include in such registration (i) first, all of the securities the Company
proposes to sell and (ii) second, the Piggyback Securities and other securities
sought to be registered, on a pro rata basis, based upon the number of
securities sought to be registered by the holders of the Piggyback Securities
and the holders of the other securities sought to be registered. If the managing
underwriter makes such a determination, the Company shall promptly advise the
holders of the Registrable Securities, in writing, that a limitation or
inclusion of fewer than all of the Piggyback Securities is likely. If a
reduction in the total amount of securities to be included in such offering is
necessary as described in the prior sentence, the Company shall not treat the
holders of the Piggyback Securities less favorably than directors, officers,
controlling stockholders and their affiliates seeking piggyback registration
rights.

               (b) Demand Registrations.

               (1) Obligation to File. At any time following the issuance of
Warrants pursuant to the Warrant Agreement, promptly upon the written request of
holders of a majority of the then outstanding Registrable Securities, the
Company will use its reasonable best efforts to file with the SEC a Registration
Statement under the Securities Act for the offering of all of the Registrable
Securities which such holders request to be registered (the "Demand
Registration"), provided, that the number of Registrable Securities to be
registered (i) are not less than 200,000 or (ii) if less than 200,000,
constitutes all of the remaining Registrable Securities. The Demand Registration
shall be on an appropriate form and the Demand Registration and any form of
prospectus included therein shall reflect such plan of distribution or method of
sale as such holders notify the Company, including the sale of some or all of
the Registrable Securities in a public offering. The Company shall use its
reasonable best efforts to cause the Demand Registration to become effective,
and, upon the request of any of such holders, keep the Demand Registration
effective for up to 60 days, unless the distribution of securities registered
thereunder has been earlier completed. During the period during which the Demand
Registration is effective, the Company shall supplement or make amendments to
the Demand Registration, if required by the Securities Act, including to reflect
any specific plan of distribution or method of sale, and shall use its
reasonable best efforts to have such supplements and amendments declared
effective, if required, as soon as practicable after filing. Notwithstanding the
foregoing, the Company shall have the right to delay any Demand Registration for
a period of not more than 90 days after the date of any request to register the
Registrable Securities pursuant to the Demand Registration, if, at the time of
such request, the Company is preparing, or within ten days thereafter engages an
underwriter, and commences in good faith to prepare,

                                       4
<PAGE>   7
a Registration Statement for a public offering (other than a registration
relating solely to employee benefit plans) which is in fact filed and becomes
effective within 90 days after the date the holders of the Registrable
Securities have provided the written registration request, or is engaged in any
material acquisition or divestiture or other business transaction with a third
party which the Board of Directors of the Company reasonably determines in good
faith would be adversely affected by the Demand Registration to the material
detriment of the Company.

               (2) Number of Demand Registrations. The Company shall be
obligated to effect, under this Section 3(b), (i) not more than two Demand
Registrations during any 12 month period covering Registrable Securities issued
or issuable within the two year period prior to the request for such Demand
Registration, and (ii) not more than one Demand Registration during any 12 month
period covering Registrable Securities issued more than two years before the
request for such Demand Registration in the event that Rule 144 of the
Securities Act does not permit such Registrable Securities to be freely
tradeable by the purchasers thereof, provided, however, that, in any event, the
Company shall not be obligated to effect more than one Demand Registration
during the 12 month period after the Company files a Registration Statement on
which holders of Registrable Securities that so elect are permitted to include
as many Piggyback Securities as such holder desires without any reduction in the
amount of such Piggyback Securities pursuant to paragraph 3(a)(2) hereof. A
Demand Registration shall not be deemed to have been effected, nor shall it be
sufficient to reduce the number of Demand Registrations available to the holders
of Registrable Securities requesting a Demand Registration under this Section
3(b), if such registration cannot be used by holders of Registrable Securities
for more than 120 days as a result of any stop order, injunction or other order
of the SEC or other government authority for any reason other than an act or
omission of such holders and all the Registrable Securities registered
thereunder are not sold.

               (3) Selection of Underwriters. Any and all underwriters or other
agents involved in any sale of Registrable Securities pursuant to a Registration
Statement contemplated by this Section 3(b) shall include such underwriter(s) or
other agent(s) as selected by the holders of a majority of Registrable
Securities being registered and approved of by the Company, which approval shall
not be unreasonably withheld; provided that any affiliate of a holder requesting
a Demand Registration shall in all events be approved by the Company.

               SECTION 4.    Registration Procedures.

               In connection with the Company's registration obligations
pursuant to Section 3 hereof, the Company will use its commercially reasonable
efforts to effect such registration to permit the sale of such Registrable
Securities in accordance with the intended methods or methods of disposition
thereof, and pursuant thereto the Company will as expeditiously as possible:

(a) before filing a Registration Statement or Prospectus or any amendments or
supplements thereto, furnish to the holders of the Registrable Securities
covered by such Registration Statement and the underwriters, if any, copies of
all such documents proposed to be

                                       5
<PAGE>   8
filed, which documents will be subject to the review of such holders and
underwriters, and the Company will not file any Registration Statement or
amendment thereto or any Prospectus or any supplement thereto to which the
holders of a majority of the Registrable Securities covered by such Registration
Statement or the underwriters, if any, shall reasonably object within three days
after such documents are delivered;

               (b) prepare and file with the SEC a Registration Statement or
Registration Statements relating to the applicable Demand Registration or
Piggyback Registration including all exhibits and financial statements required
by the SEC to be filed therewith, and use its commercially reasonable efforts to
cause such Registration Statement to become effective under the Securities Act;
and prepare and file with the SEC such amendments and post-effective amendments
to such Registration Statement, and such supplements to the Prospectus, as may
be required by the rules, regulations or instructions applicable to the
registration form utilized by the Company or by the Securities Act or rules and
regulations otherwise necessary to keep the Registration Statement effective for
a period of not less than 180 days (or such shorter period which will terminate
when all Registrable Securities covered by such Registration Statement have been
sold or withdrawn), or, if such Registration Statement relates to an
Underwritten Offering, such longer period as in the opinion of counsel for the
underwriters a Prospectus is required by law to be delivered in connection with
sales of Registrable Securities by an underwriter or dealer; and cause the
Prospectus as so supplemented to be filed pursuant to Rule 424 under the
Securities Act; and comply with the provisions of the Securities Act and the
Exchange Act with respect to the disposition of all securities covered by such
Registration Statement during the applicable period in accordance with the
intended methods of disposition by the sellers thereof set forth in such
Registration Statement or supplement to the Prospectus;

               (c) notify the selling holders of Registrable Securities and the
managing underwriters, if any, promptly;

                   (1) when the Prospectus or any Prospectus supplement or
posteffective amendment has been filed, and, with respect to the Registration
Statement or any post-effective amendment, when the same has become effective,

                   (2) of any request by the SEC during the period of
effectiveness for amendments or supplements to the Registration Statement or the
Prospectus or for additional information relating to the Registration Statement,

                   (3) of the issuance by the Commission of any stop order
suspending the effectiveness of the Registration Statement or the initiation of
any proceedings for that purpose,

                   (4) if at any time the representations and warranties of the
Company contemplated by paragraph (n) below cease to be true and correct,

                   (5) of the receipt by the Company of any notification with
respect to the suspension of the qualification of the Registrable Securities for
sale in any jurisdiction or the initiation or threatening of any proceeding for
such purpose, and

                                       6
<PAGE>   9
                   (6) of the existence of any fact known which results in the
Registration Statement, the Prospectus or any document incorporated therein by
reference containing an untrue statement of material fact or omitting to state a
material fact required to be stated therein or necessary to make the statements
therein not misleading;

               (d) make every reasonable effort to obtain the withdrawal of any
order suspending the effectiveness of the Registration Statement at the earliest
possible moment;

               (e) if requested by the managing underwriter or underwriters or a
holder of Registrable Securities being sold in connection with an Underwritten
Offering, immediately incorporate in a Prospectus supplement or post-effective
amendment such information as the managing underwriters and the holders of a
majority of the Registrable Securities being sold require to be included therein
relating to the plan of distribution with respect to such Registrable
Securities, including, without limitation, information with respect to the
amount of Registrable Securities being sold to such underwriters, the purchase
price being paid therefor by such underwriters and with respect to any other
terms of the underwritten (or best efforts underwritten) offering of the
Registrable Securities to be sold in such offering; and make all required
filings of such Prospectus supplement or post-effective amendment as soon as
notified of the matters to be incorporated in such Prospectus supplement or
post-effective amendment;

               (f) deliver to each selling holder of Registrable Securities and
the underwriters, if any, without charge, as many copies of the Prospectus
(including each preliminary prospectus) and any amendment or supplement thereto
as such Persons may reasonably request (it being understood that the Company
consents to the use of the Prospectus or any amendment or supplement thereto by
each of the selling holders of Registrable Securities and the underwriters, if
any, in connection with the offering and sale of the Registrable Securities
covered by the Prospectus or any amendment or supplement thereto) and such other
documents as such selling holder and the underwriters, if any, may reasonably
request in order to facilitate the disposition of the Registrable Securities by
such holder and underwriters, if any, but only while the Company shall be
required under the provisions hereof to cause the Registration Statement to
remain current;

               (g) prior to any public offering of Registrable Securities, use
its commercially reasonable efforts to register or qualify or cooperate with the
selling holders of Registrable Securities, the underwriters, if any, and their
respective counsel in connection with the registration or qualification of such
Registrable Securities for offer and sale under the securities or blue sky laws
of such jurisdictions as any selling holder of Registrable Securities or any
underwriter reasonably requests in writing and do any and all other acts or
things reasonably necessary to enable the disposition in such jurisdictions of
the Registrable Securities covered by the Registration Statement; provided that
the Company will not be required to qualify generally to do business in any
jurisdiction where it is not then so qualified or to take any action which would
subject it to general service of process in any such jurisdiction where it is
not then so subject;

               (h) cooperate with the selling holders of Registrable Securities
and the managing underwriters, if any, to facilitate the timely preparation and
delivery of certificates

                                       7
<PAGE>   10
representing Registrable Securities to be sold and not bearing any restrictive
legends; and enable such Registrable Securities to be in such denominations and
registered in such names as the managing underwriters may request at least two
business days prior to any sale of Registrable Securities to the underwriters;

               (i) use its commercially reasonable efforts to cause the
Registrable Securities covered by the applicable Registration Statement to be
registered with or approved by such other governmental agencies or authorities
within the U.S. as may be necessary to enable the seller or sellers thereof or
the underwriters, if any, to consummate the disposition of such Registrable
Securities; provided that the Company will not be required to qualify generally
to do business in any jurisdiction where it is not then so qualified or to take
any action which would subject it to general service of process in any such
jurisdiction where it is not then so subject;

               (j) if any fact contemplated by paragraph (c)(6) above shall
exist, prepare a supplement or post-effective amendment to the Registration
Statement or the related Prospectus or any document incorporated therein by
reference or file any other required document so that, as thereafter delivered
to the purchasers of the Registrable Securities, the Prospectus will not contain
an untrue statement of a material fact or omit to state any material fact
required to be stated therein or necessary to make the statements therein not
misleading, but only while the Company shall be required under the provisions
hereof to cause the Registration Statement to remain current;

               (k) use its commercially reasonable efforts to cause all
Registrable Securities covered by the Registration Statement to be quoted on the
NASDAQ National Market or listed on each securities exchange on which similar
securities issued by the Company are then listed;

               (l) enter into agreements (including underwriting agreements) and
take all other appropriate actions that are reasonable, necessary and in typical
form for such transactions in order to expedite or facilitate the disposition of
such Registrable Securities.

The above shall be done at the effectiveness of such Registration Statement,
each closing under any underwriting or similar agreement as and to the extent
required thereunder and from time to time as may be requested by any selling
holder in connection with the disposition of Registrable Securities pursuant to
such Registration Statement, but only while the Company shall be required under
the provisions hereof to cause the Registration Statement to remain current;

               (m) make available for inspection at reasonable times and upon
reasonable notice by a representative of the holders of a majority of the
Registrable Securities, any underwriter participating in any disposition
pursuant to such Registration Statement, and any attorney or accountant retained
by the sellers or underwriter, all financial and other records, pertinent
corporate documents and properties of the Company, and cause the Company's
officers, directors and employees to supply all information reasonably requested
by any such representative, underwriter, attorney or accountant in connection
with the registration; provided that any records, information or documents that
are designated by the Company in writing as confidential shall be kept
confidential by such Persons unless disclosure of such records, information or
documents is required by court or administrative order; and

                                       8
<PAGE>   11
               (n) otherwise use its commercially reasonable efforts to comply
with all applicable rules and regulations of the SEC, and make generally
available to its security holders, earnings statements satisfying the provisions
of Section 11(a) of the Securities Act, no later than 45 days after the end of
any fiscal quarter (or 90 days after the end of any fiscal year) (1) commencing
at the end of any fiscal quarter in which Registrable Securities are sold to
underwriters in an Underwritten Offering, or, if not sold to underwriters in
such an offering, (2) beginning with the first month of the Company's first
fiscal quarter commencing after the effective date of the Registration
Statement, which statements shall cover said 12-month periods.

               The Company may require each seller of Registrable Securities as
to which any registration is being effected to furnish to the Company such
information regarding itself, the Registrable Securities held by it and the
distribution of such securities as the Company may from time to time reasonably
request in writing, and shall take such commercially reasonable action as may be
reasonably required in order to permit the Company and any underwriters to
comply with all applicable requirements of the SEC and the NASD. Such provision
of information and materials is a condition precedent to the obligations of the
Company pursuant to this Agreement.

               Each holder of Registrable Securities agrees by acquisition of
such Registrable Securities that, upon receipt of any notice from the Company of
the happening of any event of the kind described in Sections 4(c)(3), 4(c)(4),
4(c)(5), 4(c)(6) or 4(j) hereof, such holder will forthwith discontinue
disposition of Registrable Securities until such holder's receipt of the copies
of the supplemented or amended Prospectus contemplate by Sections 4(c)(3),
4(c)(4), 4(c)(5), 4(c)(6) or 4(j) hereof, or until it is advised in writing by
the Company that the use of the Prospectus may be resumed, and has received
copies of any additional or supplemental filings which are incorporated by
reference in the Prospectus, and, if so directed by the Company, such holder
will deliver to the Company (at the Company's expense) all copies, other than
permanent file copies then in such holder's possession, of the Prospectus
covering such Registrable Securities current at the time of receipt of such
notice. In the event the Company shall give any such notice, the time periods
during which such Registration Statement shall be maintained effective shall be
extended by the number of days during the period from and including the date of
the giving of such notice to and including the date when each seller of
Registrable Securities covered by such Registration Statement either receives
the copies of the supplemented or amended prospectus contemplated by Sections
4(c)(3), 4(c)(4), 4(c)(5), 4(c)(6) or 4(j) hereof or is advised in writing by
the Company that the use of the Prospectus may be resumed.

               SECTION 5. Registration Expenses.

                  (a) All expenses incident to the Company's performance of or
compliance with this Agreement will be paid by the Company, regardless of
whether the Registration Statement becomes effective, including without
limitation:

                      (1) all registration and filing fees (including all
       filings required to be made with the SEC and the NASD;

                      (2) fees and expenses of compliance with securities or
       blue sky laws (including fees and disbursements of counsel for the
       underwriters or selling holders in

                                       9
<PAGE>   12
       connection with blue sky qualifications of the Registrable Securities and
       determination of their eligibility for investment under the laws of such
       jurisdictions as the managing underwriters or holders of a majority of
       the Registrable Securities being sold may designate);

                      (3) printing (including expenses of printing certificates
       for the Registrable Securities in a form eligible for deposit with the
       Depository Trust Company and of printing prospectus), messenger,
       telephone and delivery expenses;

                      (4) fees and disbursements of counsel for the (i) Company,
       (ii) the underwriters and (iii) the sellers of the Registrable Securities
       (subject to the provisions of Section 6(b) hereof);

                      (5) fees and disbursements of all independent certified
       public accountants of the Company (including the expenses of any special
       audit and "cold comfort" letters required by or incident to such
       performance);

                      (6) fees and disbursements of underwriters (including, if
       applicable, the fees and expenses of any "qualified independent
       underwriter" (and its counsel) that is required to be retained in
       accordance with the rules and regulations of the NASD, but excluding
       discounts, commissions or fees of underwriters, selling brokers, dealer
       managers or similar securities industry professionals relating to the
       distribution of the Registrable Securities or legal expenses of any
       Person other than the Company, the underwriters and the selling holders);

                      (7) securities acts liability insurance if the Company so
       desires or if the underwriters or selling holders of a majority of the
       Registrable Securities so require; and

                      (8) fees and expenses of other Persons retained by the
       Company,

(all such expenses being herein called "Registration Expenses").

               The Company will, in any event, pay its internal expenses
(including, without limitation, all salaries and expenses of its officers and
employees performing legal or accounting duties), the expense of any annual
audit, the fees and expenses incurred in connection with the listing of the
securities to be registered on each securities exchange on which similar
securities issued by the Company are then listed, rating agency fees and the
fees and expenses of any Person, including special experts, retained by the
Company.

               (b) In connection with each Registration Statement required
hereunder, the Company will reimburse the holders of Registrable Securities
being registered pursuant to such Registration Statement for the reasonable fees
and disbursements of not more than one counsel chosen by the holders of a
majority of such Registrable Securities.

                                       10
<PAGE>   13
               SECTION 6. Indemnification.

                   (a) Indemnification by Company. The Company agrees to
indemnify and hold harmless each holder of Registrable Securities, its officers,
directors, employees and Agents and each Person who controls such holder within
the meaning of either Section 15 of the Securities Act or Section 20 of the
Exchange Act (each such person being sometimes hereinafter referred to as an
"Indemnified Holder") from and against all losses, claims, damages, liabilities
and expenses (including reasonable costs of investigation and legal expenses)
arising out of or based upon any untrue statement or alleged untrue statement of
a material fact contained in any Registration Statement or Prospectus, in any
amendment or supplement thereto or in any preliminary prospectus, or arising out
of or based upon any omission or alleged omission to state therein a material
fact required to be stated therein or necessary to make the statements therein
not misleading, except insofar as such losses, claims, damages, liabilities or
expenses arises out of or are based upon any such untrue statement or omission
or allegation thereof based upon information furnished in writing to the Company
by or on behalf of such holder expressly for use therein; provided, however,
that the Company shall not be liable in any such case to the extent that any
such loss, claim, damage, liability or expense arises out of or is based upon an
untrue statement or alleged untrue statement or omission or alleged omission in
any such Registration Statement or Prospectus or preliminary prospectus, if such
untrue statement or alleged untrue statement, omission or alleged omission is
completely corrected in an amendment or supplement to such Registration
Statement or Prospectus or preliminary prospectus and if, having previously been
furnished by or on behalf of the Company with copies of the Prospectus or
preliminary prospectus as so amended or supplemented, such holder thereafter
fails to deliver such Prospectus or preliminary prospectus as so amended or
supplemented, prior to or concurrently with the sale of a Registrable Security
to the Person asserting such loss, claim, damage, liability or expense who
purchased such Registrable Security which is the subject thereof from such
holder. The indemnity will be in addition to any liability which the Company may
otherwise have. The Company will also indemnify underwriters, selling brokers,
dealer managers and similar securities industry professionals participating in
the distribution, their officers and directors and each Person who controls such
Persons (within the meaning of Section 15 of the Securities Act or Section 20 of
the Exchange Act) to the same extent as provided above with respect to the
indemnification of the Indemnified Holders of Registrable Securities.

                   If any action or proceeding (including any governmental
investigation or inquiry) shall be brought or asserted against an Indemnified
Holder in respect of which indemnity may be sought from the Company, such
Indemnified Holder shall promptly notify the Company in writing, and the Company
shall assume the defense thereof, including the employment of counsel
satisfactory to such Indemnified Holder and the payment of all expenses. Such
Indemnified Holder shall have the right to employ separate counsel in any such
action and to participate in the defense thereof, but the fees and expenses of
such counsel shall be at the expense of such Indemnified Holder unless (a) the
Company has agreed to pay such fees and expenses or (b) the Company shall have
failed to assume the defense of such action or proceeding and has failed to
employ counsel reasonably satisfactory to such Indemnified Holder in any such
action or proceeding (including any impleaded parties) include both such
Indemnified Holder and the Company or (c) such Indemnified Holder shall have
been advised in writing by counsel that there is a conflict of interest between
such

                                       11
<PAGE>   14
Indemnified Holder and the Company or that there are additional defenses or
claims that it may assert that are adverse to or not in the interest of the
Company and separate counsel is required to represent such interests (in which
case, if such Indemnified Holder notifies the Company in writing that it elects
to employ separate counsel at the expense of the Company, the Company shall not
have the right to assume the defense of such action or proceeding on behalf of
such Indemnified Holder, it being understood, however, that the Company shall
not, in connection with any one such action or proceeding or separate but
substantially similar or related actions or proceedings in the same jurisdiction
arising out of the same general allegations or circumstances, be liable for the
reasonable fees and expenses of more than one separate firm of attorneys at any
time for such Indemnified Holder and any other Indemnified Holders, which firm
shall be designated in writing by such Indemnified Holders). The Company shall
not be liable for any settlement of any such action or proceeding effected
without its written consent, but if settled with its written consent, or if
there be a final judgment for the plaintiff in any such action or proceeding for
which the Company received notice hereunder, the Company agrees to indemnify and
hold harmless such Indemnified Holder from and against any loss or liability by
reason of such settlement or judgment.

               (b) Indemnification by Holder of Registrable Securities. Each
holder of Registrable Securities agrees to indemnify and hold harmless the
Company, its directors and officers and each Person, if any, who controls the
Company within the meaning of either Section 15 of the Securities Act or Section
20 of the Exchange Act to the same extent as the foregoing indemnity from the
Company to such holder, but only with respect to information relating to such
holder furnished in writing by such holder expressly for use in any Registration
Statement or Prospectus, or any amendment thereto, or any preliminary
prospectus. In case any action or proceeding shall be brought against the
Company or directors or officers or any such controlling person, in respect of
which indemnity may be sought against a holder of Registrable Securities, such
holder shall have the rights and duties given the Company and the Company or its
directors or officers or such controlling person shall have the rights and
duties given to each holder by the preceding paragraph. In no event shall the
liability of any selling holder of Registrable Securities hereunder be greater
in amount than the gross amount of the proceeds (before expenses and
commissions) from the sale of Registrable Securities by such holder giving rise
to such indemnification obligation.

               The Company and each holder of Registrable Securities shall be
entitled to receive indemnities from underwriters, selling brokers, dealer
managers and similar securities industry professionals participating in the
distribution, to the same extent as provided above with respect to information
so furnished in writing by such Person specifically for inclusion in any
Prospectus or Registration Statement or any amendment or supplement thereto, or
any preliminary prospectus.

               (c) Contribution. If the indemnification provided for in this
Section 7 is unavailable to an indemnified party under Section 7(a) or Section
7(b) hereof (other than by reason of exceptions provided in those Sections) in
respect of any losses, claims, damages, liabilities or expenses referred to
therein, then each applicable indemnifying party, in lieu of indemnifying such
indemnified party, shall contribute to the amount paid or payable by such
indemnified party as a result of such losses, claims, damages, liabilities or
expenses in such proportion as is appropriate to reflect the relative fault of
the Company on the one hand and of the Indemnified Holder on the

                                       12
<PAGE>   15
other in connection with the statements or omissions which resulted in such
losses, claims, damages, liabilities or expenses, as well as any other relevant
equitable considerations. The relative fault of the Company on the one hand and
of the Indemnified Holder on the other shall be determined by reference to,
among other things, whether the untrue or alleged untrue statement of a material
fact or the omission or alleged omission to state a material fact relates to
information supplied by the Company or by the Indemnified Holder and the
parties' relative intent, knowledge, access to information and opportunity to
correct or prevent such statement or omission. The amount paid or payable by a
party as a result of the losses, subject to the limitations set forth in the
second paragraph of Section 7(a), any legal or other fees or expenses reasonably
incurred by such party in connection with investigating or defending any action
or claim.

               The Company and each holder of Registrable Securities agree that
it would not be just and equitable if contribution pursuant to this Section 7(c)
were determined by pro rata allocation or by any other method of allocation
which does not take account of the equitable considerations referred to in the
immediately preceding paragraph. Notwithstanding the provisions of this Section
7(c), an Indemnified Holder shall not be required to contribute any amount in
excess of the amount by which the total price at which the Securities sold by
such Indemnified Holder or its affiliated Indemnified Holders and distributed to
the public were offered to the public exceeds the amount of any damages which
such Indemnified Holder or its affiliated Indemnified Holder, has otherwise been
required to pay by reason of such untrue or alleged untrue statement or omission
or alleged omission. No person guilty of fraudulent misrepresentation (within
the meaning of Section 11(f) of the Act) shall be entitled to contribution from
any person who was not guilty of such fraudulent misrepresentation.

               SECTION 7. Rule 144.

               The Company covenants that it will file the reports required to
be filed by it under the Securities Acts and the Exchange Act and rules and
regulations adopted by the SEC thereunder (or, if the Company is not required to
file such reports, it will, upon the request of any holder of Registrable
Securities made after the first anniversary of the date hereof, make publicly
available such information as necessary to permit sales pursuant to Rule 144
under the Securities Act), and it will take such further action as any holder of
Registrable Securities may reasonably request, all to the extent required from
time to time to enable such holder to sell Registrable Securities without
registration under the Securities Act within the limitation of the exemptions
provided by (a) Rule 144 under the Securities Act, as such Rule may be amended
from time to time, or (b) any similar rule or regulation hereafter adopted by
the SEC. Upon the request of any holder of Registrable Securities, the Company
will deliver to such holder a written statement as to whether it had complied
with such information and requirements.

               SECTION 8. Participation in Underwritten Registrations.

               No Person may participate in any Underwritten Registration
hereunder unless such Person (a) agrees to sell such Person's securities on the
basis provided in any underwriting arrangements approved by the Persons entitled
hereunder to approve such arrangements and (b) completes and executes all
questionnaires, powers of attorney, indemnities, underwriting agreements and
other documents required under the terms of such underwriting arrangements.

                                       13
<PAGE>   16
               SECTION 9. Miscellaneous.

                   (a) Termination. The registration rights set forth in this
Agreement shall terminate (a) at any time, upon mutual agreement in writing of
the Parties hereto or (b) upon such time as all of the Registrable Securities
then held by the parties hereto can be sold by such parties in a three-month
period in accordance with Rule 144 under the Securities Act. Notwithstanding the
foregoing, the obligations of each party to this Agreement pursuant to Section
12 hereof, shall survive the termination of registration rights sets forth in
this Agreement.

                   (b) No Inconsistent Agreements. The Company will not on or
after the date of this Agreement enter into any agreement with respect to its
securities which is inconsistent with the rights granted to the holders of
Registrable Securities in this Agreement or otherwise conflicts with the
provisions hereof.

                   (c) Adjustments Affecting Registrable Securities. The Company
will not take any action, or permit any change to occur, with respect to the
Registrable Securities which would (i) adversely affect the ability of the
holders of Registrable Securities to include such Registrable Securities in a
registration undertaken pursuant to this Agreement or (ii) adversely affect the
marketability of such Registrable Securities in any such registration.

                   (d) Amendments and Waivers. The provisions of this Agreement,
including the provisions of this sentence, may not be amended, modified or
supplemented, and waivers or consents to departures from the provisions hereof
may not be given without the written consent of the Company and holders of at
least a majority of the outstanding Registrable Securities affected by such
amendment. Notwithstanding the foregoing, a waiver or consent to departure from
the provisions hereof that relates exclusively to the rights of holders of
Registrable Securities whose securities are being sold pursuant to a
Registration Statement and that does not directly or indirectly affect the
rights of other holders of Registrable Securities may be given by the holders of
a majority of the Registrable Securities being sold.

                   (e) Notices. All notices and other communications provided
for or permitted hereunder shall be made in writing by hand-delivery, registered
first-class mail, telex, telecopier, or air courier guaranteeing overnight
delivery:

                       (i) if to a holder of Registrable Securities, at the most
            current address given by such holder to the Company in accordance
            with the provisions of this Section 10(e).

                     With a copy to:

                               Stroock & Stroock & Lavan LLP
                               2029 Century Park East, 16th Floor
                               Los Angeles, California 90067
                               Facsimile:  310-556-5959
                               Attention:  Gregory A. Bray, Esq.

                                       14
<PAGE>   17
                        (ii)   if to the Company, initially to:

                               Komag, Incorporated
                               1710 Automation Parkway
                               San Jose, California 95131-1873
                               Facsimile:  408-944-9234
                               Attention: Chief Financial Officer

                        and thereafter at such other address, notice of which is
                        given in accordance with the provisions of this Section
                        10(e),

                        With a copy to:

                                      Wilson Sonsini Goodrich & Rosati
                                      650 Page Mill Road
                                      Palo Alto, California 94304-1050
                                      Facsimile:  650-493-6811
                                      Attn:  Alan K. Austin, Esq.

               All such notices and communications shall be deemed to have been
duly given: at the time delivered by hand, if personally delivered; five
business days after being deposited in the mail, postage prepaid, if mailed;
when answered back, if telexed; when receipt acknowledged, if telecopied; and on
the next business day, if timely delivered to an air courier guaranteeing
overnight delivery.

               (f) Successors and Assigns. This Agreement shall inure to the
benefit of and be binding upon the successors and assigns of each of the
parties, including without limitation and without the need for an express
assignment, subsequent permitted holders of Registrable Securities.

               (g) Counterparts. This Agreement may be executed in any number of
counterparts and by the parties hereto in separate counterparts, each of which
when so executed shall be deemed to be an original and all of which taken
together shall constitute one and the same agreement.

               (h) Headings. The headings in this Agreement are for convenience
of reference only and shall not limit or otherwise affect the meaning hereof.

               (i) Governing Law. This Agreement shall be governed by and
construed in accordance with the laws of the State of California.

               (j) Severability. In the event that any one or more of the
provisions contained herein, or the application thereof in any circumstance, is
held invalid, illegal or unenforceable, the validity, legality and
enforceability of any such provision in every other respect and of the remaining
provisions contained herein shall not be affected or impaired thereby.

                                       15
<PAGE>   18
               (k) Entire Agreement. This Agreement is intended by the parties
as a final expression of their agreement and intended to be a complete and
exclusive statement of the agreement and understanding of the parties hereto in
respect of the subject matter contained herein. There are no restrictions,
promises, warranties or undertakings, other than those set forth or referred to
herein with respect to the registration rights granted by the Company with
respect to the securities sold pursuant to the Purchase Agreement. This
Agreement supersedes all prior agreements and understandings between the parties
with respect to such subject matter.

                           [Signature Pages To Follow]

                                       16
<PAGE>   19
                             IN WITNESS WHEREOF, the parties have executed this
Agreement as of the date first written above.

KOMAG, INCORPORATED

By:
   ----------------------------
Title:
      -------------------------

Address:
1710 Automation Parkway
San Jose, California 95131-1873
Facsimile: (408) 944-9234
Attention:  Chief Financial Officer

FLEET NATIONAL BANK f/k/a BANKBOSTON, N.A.,
as Restructure Agent and as a Restructure Lender

By:
   ----------------------------
Title:
      -------------------------

Address:
100 Federal Street, Mail Stop 01-06-01
Boston, MA 02110
Facsimile:  (617) 434-4775
Attention:  Donald Sheehan

BANK OF MONTREAL, as a Restructure Lender

By:
   ----------------------------
Title:
      -------------------------

Address:
115 S. LaSalle Street, 12 West
Chicago, IL 60603
Facsimile:  (312) 750-6057
Attention:  Jack J. Kane

                                      S-1
<PAGE>   20
BEAR, STEARNS & CO. INC.,
as a Restructure Lender

By:
   ----------------------------
Title:
      -------------------------

Address:
245 Park Avenue
New York, New York  10167
Facsimile:  (212) 272-8102
Attention:
          ---------------------

COMERICA BANK - CALIFORNIA,
as a Restructure Lender

By:
   ----------------------------
Title:
      -------------------------

Address:
55 Almaden Boulevard
Mail Code: 4041
San Jose, California  95113
Facsimile: (408) 556-5855
Attention:  Carol A. Palestro

OLYMPUS SECURITIES, LTD.,
as a Restructure Lender

By:
   ----------------------------
Title:
      -------------------------

Address:
c/o Citadel Investment Group, LLC
225 West Washington Street, 9th Floor
Chicago, Illinois  60606
Facsimile:  (312) 368-4650
Attention:  Bradford Couri

                                      S-2
<PAGE>   21
NELSON PARTNERS LTD.,
as a Restructure Lender

By:
   ----------------------------
Title:
      -------------------------

Address:
c/o Citadel Investment Group, LLC
225 West Washington Street, 9th Floor
Chicago, Illinois  60606
Facsimile:  (312) 368-4650
Attention:  Bradford Couri

THE BANK OF NOVA SCOTIA,
as a Restructure Lender

By:
   ----------------------------
Title:
      -------------------------

Address:
One Liberty Plaza
New York, New York 10006
Facsimile:  (212) 225-5205
Attention:  Norm Gillespie

UNION BANK OF CALIFORNIA, N.A.,
as a Restructure Lender

By:
   ----------------------------
Title:
      -------------------------

Address:
350 California Street, 7th Floor
San Francisco, California  94104
Facsimile:  (415) 705-7390
Attention:  Christiana Creekpaum

                                      S-3
<PAGE>   22
LOEB PARTNERS CORPORATION,
as a Restructure Lender

By:
   ----------------------------
Title:
      -------------------------

Address:
61 Broadway, 24th Floor
New York, New York  10006
Facsimile:  (212) 574-2003
Attention:  Robert Grubin

THE DAI-ICHI KANGYO BANK, LIMITED,
as a Restructure Lender

By:
   ----------------------------
Title:
      -------------------------

Address:
Corporate Finance Department I
One World Trade Center, Suite 4911
New York, NY 10048
Facsimile:  (212) 912-1879
Attention:  Nelson Chang

THE INDUSTRIAL BANK OF JAPAN, LIMITED,
as a Restructure Lender

By:
   ----------------------------
Title:
      -------------------------

Address:
One Market Street
Spear Tower, Suite 1610
San Francisco, California  94105
Facsimile:  (415) 982-1917
Attention:  Joseph A. Endoso

                                      S-4
<PAGE>   23
THE MITSUBISHI TRUST AND BANKING CORPORATION,
as a Restructure Lender

By:
   ----------------------------
Title:
      -------------------------

Address:
520 Madison Avenue, 26th Floor
New York, NY 10022
Facsimile:  (212) 644-6825
Attention:  Daniel Chang

SANWA BANK CALIFORNIA,
as a Restructure Lender

By:
   ----------------------------
Title:
      -------------------------

Address:
444 Market Street, 22nd Floor
San Francisco, CA 94111
Facsimile:  (415) 597-5491
Attention:  George Vetek

BANK ONE, N.A.
as a Restructure Lender

By:
   ----------------------------
Title:
      -------------------------

Address:
Bank One, N.A.
Western Region Managed Assets
AZ1-1283
201 N. Central Avenue
Phoenix, AZ 85004-2267
Facsimile:  (602) 221-1737
Attention:  Dennis B. Warren

                                      S-5
<PAGE>   24
THE FUJI BANK, LIMITED,
as a Restructure Lender

By:
   ----------------------------
Title:
      -------------------------

Address:
333 South Hope Street
Los Angeles, CA  90071
Facsimile:  (213) 253-4178
Attention:
          ---------------------

THE SUMITOMO BANK, LIMITED,
as a Restructure Lender

By:
   ----------------------------
Title:
      -------------------------

Address:
555 California Street, Suite 3350
San Francisco, California  94104
Facsimile: (415) 362-6527
Attention:  Azar Shakeri

                                      S-6

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