# mdadm.conf

## NAME



           mdadm.conf - configuration for management of Software RAID with
           mdadm
    


## SYNOPSIS



           /etc/mdadm.conf
    


## DESCRIPTION



           _mdadm_ is a tool for creating, managing, and monitoring RAID
           devices using the **md** driver in Linux.
    
           Some common tasks, such as assembling all arrays, can be
           simplified by describing the devices and arrays in this
           configuration file.
    
       **SYNTAX**
           The file should be seen as a collection of words separated by
           white space (space, tab, or newline).  Any word that beings with a
           hash sign (#) starts a comment and that word together with the
           remainder of the line is ignored.
    
           Spaces can be included in a word using quotation characters.
           Either single quotes (**'**) or double quotes (**"**) may be used.  All
           the characters from one quotation character to next identical
           character are protected and will not be used to separate words to
           start new quoted strings.  To include a single quote it must be
           between double quotes.  To include a double quote it must be
           between single quotes.
    
           Any line that starts with white space (space or tab) is treated as
           though it were a continuation of the previous line.
    
           Empty lines are ignored, but otherwise each (non continuation)
           line must start with a keyword as listed below.  The keywords are
           case insensitive and can be abbreviated to 3 characters.
    
           The keywords are:
    
           **DEVICE** A **device** line lists the devices (whole devices or
                  partitions) that might contain a component of an MD array.
                  When looking for the components of an array, _mdadm_ will
                  scan these devices (or any devices listed on the command
                  line).
    
                  The **device** line may contain a number of different devices
                  (separated by spaces) and each device name can contain wild
                  cards as defined by glob(7).
    
                  Also, there may be several device lines present in the
                  file.
    
                  Alternatively, a **device** line can contain either or both of
                  the  words **containers** and **partitions**.  The word **containers**
                  will cause _mdadm_ to look for assembled CONTAINER arrays and
                  included them as a source for assembling further arrays.
    
                  The word _partitions_ will cause _mdadm_ to read
                  _/proc/partitions_ and include all devices and partitions
                  found therein.  _mdadm_ does not use the names from
                  _/proc/partitions_ but only the major and minor device
                  numbers.  It scans _/dev_ to find the name that matches the
                  numbers.
    
                  If no DEVICE line is present in any config file, then
                  "DEVICE partitions containers" is assumed.
    
                  For example:
    
                  DEVICE /dev/hda* /dev/hdc*
                  DEV    /dev/sd*
                  DEVICE /dev/disk/by-path/pci*
                  DEVICE partitions
    
           **ARRAY** The ARRAY lines identify actual arrays.  The second word on
                  the line may be the name of the device where the array is
                  normally assembled, such as **/dev/md1** or **/dev/md/backup**.  If
                  the name does not start with a slash ('**/** '), it is treated
                  as being in **/dev/md/**.  Alternately the word **< ignore>**
                  (complete with angle brackets) can be given in which case
                  any array which matches the rest of the line will never be
                  automatically assembled.  If no device name is given, _mdadm_
                  will use various heuristics to determine an appropriate
                  name.
    
                  Subsequent words identify the array, or identify the array
                  as a member of a group. If multiple identities are given,
                  then a component device must match ALL identities to be
                  considered a match.  Each identity word has a tag, and
                  equals sign, and some value.  The tags are:
    
               **uuid=** The value should be a 128 bit uuid in hexadecimal, with
                      punctuation interspersed if desired.  This must match
                      the uuid stored in the superblock.
    
               **super-minor=**
                      The value is an integer which indicates the minor
                      number that was stored in the superblock when the array
                      was created. When an array is created as /dev/mdX, then
                      the minor number X is stored.
    
               **devices=**
                      The value is a comma separated list of device names or
                      device name patterns.  Only devices with names which
                      match one entry in the list will be used to assemble
                      the array.  Note that the devices listed there must
                      also be listed on a DEVICE line.
    
               **level=** The value is a RAID level.  This is not normally used
                      to identify an array, but is supported so that the
                      output of
    
                      **mdadm --examine --scan**
    
                      can be use directly in the configuration file.
    
               **num-devices=**
                      The value is the number of devices in a complete active
                      array.  As with **level=** this is mainly for compatibility
                      with the output of
    
                      **mdadm --examine --scan**.
    
               **spares=**
                      The value is a number of spare devices to expect the
                      array to have.  The sole use of this keyword and value
                      is as follows: **mdadm --monitor** will report an array if
                      it is found to have fewer than this number of spares
                      when **--monitor** starts or when **--oneshot** is used.
    
               **spare-group=**
                      The value is a textual name for a group of arrays.  All
                      arrays with the same **spare-group** name are considered to
                      be part of the same group.  The significance of a group
                      of arrays is that _mdadm_ will, when monitoring the
                      arrays, move a spare drive from one array in a group to
                      another array in that group if the first array had a
                      failed or missing drive but no spare.
    
               **bitmap=**
                      The option specifies a file in which a write-intent
                      bitmap should be found.  When assembling the array,
                      _mdadm_ will provide this file to the **md** driver as the
                      bitmap file.  This has the same function as the
                      **--bitmap-file** option to **--assemble**.
    
               **metadata=**
                      Specify the metadata format that the array has.  This
                      is mainly recognised for comparability with the output
                      of **mdadm -Es**.
    
               **container=**
                      Specify that this array is a member array of some
                      container.  The value given can be either a path name
                      in /dev, or a UUID of the container array.
    
               **member=**
                      Specify that this array is a member array of some
                      container.  Each type of container has some way to
                      enumerate member arrays, often a simple sequence
                      number.  The value identifies which member of a
                      container the array is.  It will usually accompany a
                      "container=" word.
    
           **MAILADDR**
                  The **mailaddr** line gives an E-mail address that alerts
                  should be sent to when _mdadm_ is running in **--monitor** mode
                  (and was given the **--scan** option).  There should only be
                  one **MAILADDR** line and it should have only one address.  Any
                  subsequent addresses are silently ignored.
    
           **MAILFROM**
                  The **mailfrom** line (which can only be abbreviated to at
                  least 5 characters) gives an address to appear in the
                  "From" address for alert mails.  This can be useful if you
                  want to explicitly set a domain, as the default from
                  address is "root" with no domain.  All words on this line
                  are catenated with spaces to form the address.
    
                  Note that this value cannot be set via the _mdadm_
                  commandline.  It is only settable via the config file.
                  There should only be one **MAILADDR** line and it should have
                  only one address.  Any subsequent addresses are silently
                  ignored.
    
           **PROGRAM**
                  The **program** line gives the name of a program to be run when
                  **mdadm --monitor** detects potentially interesting events on
                  any of the arrays that it is monitoring.  This program gets
                  run with two or three arguments, they being the Event, the
                  md device, and possibly the related component device.
    
                  There should only be one **program** line and it should be
                  given only one program.  Any subsequent programs are
                  silently ignored.
    
           **CREATE** The **create** line gives default values to be used when
                  creating arrays, new members of arrays, and device entries
                  for arrays.
    
                  There should only be one **create** line.  Any subsequent lines
                  will override the previous settings.
    
                  Keywords used in the _CREATE_ line and supported values are:
    
               **owner=**
    
               **group=** These can give user/group ids or names to use instead
                      of system defaults (root/wheel or root/disk).
    
               **mode=** An octal file mode such as 0660 can be given to
                      override the default of 0600.
    
               **metadata=**
                      The name of the metadata format to use if none is
                      explicitly given.  This can be useful to impose a
                      system-wide default of version-1 superblocks.
    
               **names=yes**
                      It has been possible to create **md** devices with a name
                      like **md_home** rather than just a number, like **md3**.
                      _mdadm_ will use the numeric alternative by default as
                      other tools that interact with md arrays may expect
                      only numbers.  If **names=yes** is given in _mdadm.conf_ then
                      _mdadm_ will use a name when appropriate.  If **names=no** is
                      given, then non-numeric _md_ device names will not be
                      used even if the default changes in a future release of
                      _mdadm_.
    
               **bbl=no** By default, _mdadm_ will reserve space for a bad block
                      list (bbl) on all devices included in or added to any
                      array that supports them.  Setting **bbl=no** will prevent
                      this, so newly added devices will not have a bad block
                      log.
    
           **HOMEHOST**
                  The **homehost** line gives a default value for the **--homehost=**
                  option to mdadm.  There should normally be only one other
                  word on the line.  It should either be a host name, or one
                  of the special words **< system>, <none> **and **< ignore>**.  If
                  **< system> **is given, then the **gethostname**(**2**) systemcall is
                  used to get the host name.  This is the default.
    
                  If **< ignore> **is given, then a flag is set so that when
                  arrays are being auto-assembled the checking of the
                  recorded _homehost_ is disabled.  If **< ignore> **is given it is
                  also possible to give an explicit name which will be used
                  when creating arrays.  This is the only case when there can
                  be more that one other word on the **HOMEHOST** line.  If there
                  are other words, or other **HOMEHOST** lines, they are silently
                  ignored.
    
                  If **< none> **is given, then the default of using
                  **gethostname**(**2**) is over-ridden and no homehost name is
                  assumed.
    
                  When arrays are created, this host name will be stored in
                  the metadata.  When arrays are assembled using auto-
                  assembly, arrays which do not record the correct homehost
                  name in their metadata will be assembled using a "foreign"
                  name.  A "foreign" name alway ends with a digit string
                  preceded by an underscore to differentiate it from any
                  possible local name. e.g.  **/dev/md/1_1** or **/dev/md/home_0**.
    
           **HOMECLUSTER**
                  The **homcluster** line gives a default value for the
                  **--homecluster=** option to mdadm.  It specifies  the  cluster
                  name for the md device.  The md device can be assembled
                  only on the cluster which matches the name specified. If
                  **homcluster** is not provided, mdadm tries to detect the
                  cluster name automatically.
    
                  There should only be one **homecluster** line.  Any subsequent
                  lines will be silently ignored.
    
           **AUTO** A list of names of metadata format can be given, each
                  preceded by a plus or minus sign.  Also the word _homehost_
                  is allowed as is _all_ preceded by plus or minus sign.  _all_
                  is usually last.
    
                  When _mdadm_ is auto-assembling an array, either via
                  _--assemble_ or _--incremental_ and it finds metadata of a
                  given type, it checks that metadata type against those
                  listed in this line.  The first match wins, where _all_
                  matches anything.  If a match is found that was preceded by
                  a plus sign, the auto assembly is allowed.  If the match
                  was preceded by a minus sign, the auto assembly is
                  disallowed.  If no match is found, the auto assembly is
                  allowed.
    
                  If the metadata indicates that the array was created for
                  _this_ host, and the word _homehost_ appears before any other
                  match, then the array is treated as a valid candidate for
                  auto-assembly.
    
                  This can be used to disable all auto-assembly (so that only
                  arrays explicitly listed in mdadm.conf or on the command
                  line are assembled), or to disable assembly of certain
                  metadata types which might be handled by other software.
                  It can also be used to disable assembly of all foreign
                  arrays - normally such arrays are assembled but given a
                  non-deterministic name in **/dev/md/**.
    
                  The known metadata types are **0.90** , **1.x** , **ddf** , **imsm**.
    
                  **AUTO** should be given at most once.  Subsequent lines are
                  silently ignored.  Thus a later config file in a config
                  directory will not overwrite the setting in an earlier
                  config file.
    
           **POLICY** This is used to specify what automatic behavior is allowed
                  on devices newly appearing in the system and provides a way
                  of marking spares that can be moved to other arrays as well
                  as the migration domains.  _Domain_ can be defined through
                  _policy_ line by specifying a domain name for a number of
                  paths from **/dev/disk/by-path/**.  A device may belong to
                  several domains. The domain of an array is a union of
                  domains of all devices in that array.  A spare can be
                  automatically moved from one array to another if the set of
                  the destination array's _domains_ contains all the _domains_ of
                  the new disk or if both arrays have the same _spare-group_.
    
                  To update hot plug configuration it is necessary to execute
                  **mdadm --udev-rules= <path_to_file> **e.g.
                  **/etc/udev/rules.d/65-md-bare.rules** command after changing
                  the config file. And also run **udevadm control --reload**
                  otherwise, a reboot is needed.
    
                  Keywords used in the _POLICY_ line and supported values are:
    
               **domain=**
                      any arbitrary string
    
               **metadata=**
                      0.9 1.x ddf or imsm
    
               **path=** file glob matching anything from **/dev/disk/by-path**
    
               **type=** either **disk** or **part**.
    
               **action=**
                      include, re-add, spare, spare-same-slot, or force-spare
    
               **auto=** yes, no, or homehost.
    
               The _action_ item determines the automatic behavior allowed for
               devices matching the _path_ and _type_ in the same line.  If a
               device matches several lines with different _actions_ then the
               most permissive will apply. The ordering of policy lines is
               irrelevant to the end result.
    
               **include**
                      allows adding a disk to an array if metadata on that
                      disk matches that array
    
               **re-add** will include the device in the array if it appears to
                      be a current member or a member that was recently
                      removed and the array has a write-intent-bitmap to
                      allow the **re-add** functionality.
    
               **spare** as above and additionally: if the device is bare it can
                      become a spare if there is any array that it is a
                      candidate for based on domains and metadata.
    
               **spare-same-slot**
                      as above and additionally if given slot was used by an
                      array that went degraded recently and the device
                      plugged in has no metadata then it will be
                      automatically added to that array (or it's container)
    
               **force-spare**
                      as above and the disk will become a spare in remaining
                      cases
    
           **PART-POLICY**
                  This is similar to **POLICY** and accepts the same keyword
                  assignments.  It allows a consistent set of policies to
                  applied to each of the partitions of a device.
    
                  A **PART-POLICY** line should set _type=disk_ and identify the
                  path to one or more disk devices.  Each partition on these
                  disks will be treated according to the _action=_ setting
                  from this line.  If a _domain_ is set in the line, then the
                  domain associated with each patition will be based on the
                  domain, but with "**-part** N" appended, when N is the partition
                  number for the partition that was found.
    
           **SYSFS** The **SYSFS** line lists custom values of MD device's sysfs
                  attributes which will be stored in sysfs after the array is
                  assembled. Multiple lines are allowed and each line has to
                  contain the uuid or the name of the device to which it
                  relates.  Lines are applied in reverse order.
    
               **uuid=** hexadecimal identifier of MD device. This has to match
                      the uuid stored in the superblock.
    
               **name=** name of the MD device as was given to _mdadm_ when the
                      array was created. It will be ignored if **uuid** is not
                      empty.
    
           **MONITORDELAY**
                  The **monitordelay** line gives a delay in seconds _mdadm_ shall
                  wait before pooling md arrays when _mdadm_ is running in
                  **--monitor** mode.  **-d/--delay** command line argument takes
                  precedence over the config file.
    
                  If multiple **MINITORDELAY** lines are provided, only first
                  non-zero value is considered.
    
           **ENCRYPTION_NO_VERIFY**
                  The **ENCRYPTION_NO_VERIFY** disables encryption verification
                  for devices with particular encryption support detected.
                  Currently, only verification of SATA OPAL encryption can be
                  disabled.  It does not disable ATA security encryption
                  verification.  Currently effective only for _IMSM_ metadata.
                  Available parameter _sata_opal ._
    


## FILES



       **/etc/mdadm.conf**
           The default config file location, used when _mdadm_ is running
           without --config option.
    
       **/etc/mdadm.conf.d**
           The default directory with config files. Used when _mdadm_ is
           running without --config option, after successful reading of the
           **/etc/mdadm.conf** default config file. Files in that directory are
           read in lexical order.
    
       **/etc/mdadm/mdadm.conf**
           Alternative config file that is read, when _mdadm_ is running
           without --config option and the **/etc/mdadm.conf** default config
           file was not opened successfully.
    
       **/etc/mdadm/mdadm.conf.d**
           The alternative directory with config files. Used when _mdadm_ is
           runninng without --config option, after reading the
           **/etc/mdadm/mdadm.conf** alternative config file whether it was
           successful or not. Files in that directory are read in lexical
           order.
    


## EXAMPLE



           DEVICE /dev/sd[bcdjkl]1
           DEVICE /dev/hda1 /dev/hdb1
    
           # /dev/md0 is known by its UUID.
           ARRAY /dev/md0 UUID=3aaa0122:29827cfa:5331ad66:ca767371
           # /dev/md1 contains all devices with a minor number of
           #   1 in the superblock.
           ARRAY /dev/md1 superminor=1
           # /dev/md2 is made from precisely these two devices
           ARRAY /dev/md2 devices=/dev/hda1,/dev/hdb1
    
           # /dev/md4 and /dev/md5 are a spare-group and spares
           #  can be moved between them
           ARRAY /dev/md4 uuid=b23f3c6d:aec43a9f:fd65db85:369432df
                      spare-group=group1
           ARRAY /dev/md5 uuid=19464854:03f71b1b:e0df2edd:246cc977
                      spare-group=group1
           # /dev/md/home is created if need to be a partitionable md array
           # any spare device number is allocated.
           ARRAY /dev/md/home UUID=9187a482:5dde19d9:eea3cc4a:d646ab8b
                      auto=part
           # One domain comprising of devices attached to specified paths is
           defined.
           # Bare device matching first path will be made an imsm spare on
           hot plug.
           # If more than one array is created on devices belonging to
           domain1 and
           # one of them becomes degraded, then any imsm spare matching any
           path for
           # given domain name can be migrated.
           POLICY domain=domain1 metadata=imsm path=pci-0000:00:1f.2-scsi-*
                      action=spare
           POLICY domain=domain1 metadata=imsm
           path=pci-0000:04:00.0-scsi-[01]*
                      action=include
           MAILADDR root@mydomain.tld
           PROGRAM /usr/sbin/handle-mdadm-events
           CREATE group=system mode=0640 auto=part-8
           HOMEHOST <system>
           AUTO +1.x homehost -all
           SYSFS name=/dev/md/raid5 group_thread_cnt=4 sync_speed_max=1000000
           SYSFS uuid=bead5eb6:31c17a27:da120ba2:7dfda40d group_thread_cnt=4
           sync_speed_max=1000000
           MONITORDELAY 60
           ENCRYPTION_NO_VERIFY sata_opal
    


* * *