From: paul@hal.COM (Paul Sander)
Newsgroups: comp.unix.aux
Subject: Re: Restoring root partition dumps
Date: 9 Jan 93 05:03:02 GMT
Organization: HaL Computer Systems, Inc.
NNTP-Posting-Host: parlo.hal.com

In article <1362@jagubox.gsfc.nasa.gov> jim@jagubox.gsfc.nasa.gov (Jim
Jagielski) writes:
>paul@hal.COM (Paul Sander) writes:
>
>>In article <1359@jagubox.gsfc.nasa.gov> jim@jagubox.gsfc.nasa.gov (Jim
>>Jagielski) writes:
>
>>>I think to do this right, you'd need to make the "backup" partition as a
>>>/usr-type file system (using 'dp')... When you need to boot up with it,
>>>use A/UX Startup's 'dp' to change it to 'Root&Usr' file system and change
>>>your "real" Root file system to something else (/usr-type)...
>>>
>>>A/UX Startup should bootup from the backup partition.
>
>>Or, you can use Apple's HD setup to create more than one root partition
>>and select the proper one from the A/UX Startup's Preferences menu.
>
>I doubt it... HD Setup will create the two file systems and give both of
>them a slice # of 0... Thus, there would be no way for A/UX Startup
>to know which slice0 to use. That's the reason for keeping the backup
>and something like Free User (slice 3) and then resetting it to Root
>(slice 0) only when needed.

Jim is correct, and I was in error when I claimed that Apple's HD setup
program would create two root partitions.  It does not permit that.  However,
I do believe that using dp and giving two partitions a name of "UNIX Root
slice 0" and type "Apple_UNIX_SVR2" will work.  The A/UX startup program
requires a slice (partition) number, so this is how it decides which slice0
to use.  The boot and in_use flags have to be set properly, by the way.

As an aside:  I really do have two root partitions, but they are on two
different disks.  I remember having major hassles with getting a small
disaster recover partition built, but that turned out to be an HFS partition.
I was able to get two of them to work; I created the two HFS partitions with
the software provided with my disk, then using Apples software to create the
A/UX partitions.  Now I have two bootable HFS partitions on one drive, and I
can launch A/UX from either one.  And both can be mounted on the desktop
under A/UX.

For the curious, this is how my backup root partition is configured:

DPM Index: 4
Name: "UNIX Root slice 0", Type: "Apple_UNIX_SVR2"
Physical: 40000 @ 200128, Logical: 40000 @ 0
Status:
        valid   alloc   in_use  not boot
        read    write
Slice 0 (clustered)
Regular UNIX File System (1)
Cluster:   0    Type: RFS       Inode: 1
Made: [0] Wed Dec 31 16:00:00 1969
Mount: [0] Wed Dec 31 16:00:00 1969
Umount: [0] Wed Dec 31 16:00:00 1969
No mount point
No AltBlk map

And this is my normal boot root:

DPM Index: 3
Name: "A/UX_Root", Type: "Apple_UNIX_SVR2"
Physical: 307462 @ 101077, Logical: 307462 @ 0
Status:
        valid   alloc   not in_use      not boot
        read    write
Slice 0 (clustered)
Regular UNIX File System (1)
Cluster:   0    Type: RFS       Inode: 1
Made: [0] Wed Dec 31 16:00:00 1969
Mount: [0] Wed Dec 31 16:00:00 1969
Umount: [0] Wed Dec 31 16:00:00 1969
No mount point
No AltBlk map


Yeah, it looks strange; the real root partition that is mounted has the
"no in_use" indicator.  This is the output of dp as invoked on slice 31
on my disks.  Both of these partitions boot, by the way.
-- 
Paul M. Sander  (408) 379-7000  |  "If everything were easy, where would be
HaL Computer Systems, Inc.      |   the challenge?"
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