how to recover from a damaged system disk?

[Bradley T. Freese]

jdh at bu-pub.bu.edu (Jason Heirtzler) writes:

> Can someone who understands the boot procedure in AIX 3.1 explain
> how you recover from a damaged system disk, or alternatively how
> to restore the whole system from a backup tape?  The procedure of
> actually restoring the files from tape is pretty straight forward,
> but there's some special magic involved in making the system
> partitions.   It looks like bosboot or mkboot can make a bootable
> disk or tape, but what to do beyond that is pretty confusing.

Boot from a set of maintenance diskettes and select the tape as your
installation source.  Put the backup tape in the drive and continue
with the installation.  This will recreate/restore / and /usr.  You
will have to use 'smit' to re-define your devices (printers and
terminals, etc.).

> If you boot from a floppy diskette, does this create a ram disk, or
> does this copy something to the paging area and boot from there, like
> BSDish unixes do?  Also, what's the significance of the logical volume
> named /blv?  Are there any special requirements, like using contigious
> physical partitions there or on the root lv?

The maintenance diskettes create a ram disk; they do not use the hard
disks.  The bootstrap logical volume is /blv.  It contains the system
images that boot the system.  It has to be in the root LV, but does
not require contiguous PPs.

> At the moment, the only choice that I have is to reinstall the entire
> system from the distribution tapes and then restore the user partitions
> and then work back from there.  With more than a Gigabyte or two, it's
> a pretty scary prospect.  Thanks for any light you can shed,

If the user partitions (I assume you mean LVs) are/were in the root
VG, the reinstall will leave them alone.  You may need to edit
/etc/filesystems and replace the entries.  If the user LVs are in
another VG, you may need to re-import the VG using 'importvg'.

Hope this helps.  Good luck.