Recover /etc/filesystems info from alternate rootvg disk

Step-by-step guide to recover missing filesystem info in /etc/filesystems from the alternate root volume group during OS migration:

Recover /etc/filesystems info from alternate rootvg disk:

1: Check if filesystem info is missing
# cat /etc/filesystems | grep lv_name
If no output, filesystem info might be missing or corrupted.

2: Wake up the alternate rootvg disk
Replace hdiskX with the actual alternate rootvg disk identifier:
# alt_rootvg_op -W -d hdiskX

3: Locate the backup /etc/filesystems file on alternate rootvg
# cd /alt_inst/etc
# ls -l filesystems*
Check timestamps and file size to identify the most recent valid filesystems backup, for example filesystems.XXXX.

4: Copy the recovered filesystems file back to /etc/
# cp filesystems.XXXX /etc/filesystems
Replace filesystems.XXXX with the actual filename found.

5: Return alternate disk to sleep
# cd /
# alt_rootvg_op -S -d hdiskX

6: Mount all filesystems from /etc/filesystems
# mount -a
or 

# mount <FS>

Summary:

• You wake the alt_rootvg disk to access the backup filesystem info.
• Copy the valid filesystems file to the active rootvg /etc/ directory.
• Put the alt_rootvg disk back to sleep.
• Then remount all filesystems with the recovered info.