How to Recover From Improper /etc/vfstab Entries (Command Line)

If you have made an incorrect entry in the /etc/vfstab file, for example, when mirroring root (/), the system will appear at first to be booting properly then fail. To remedy this situation, you need to edit /etc/vfstab while in single-user mode.

The high-level steps to recover from improper /etc/vfstab file entries are:

• Booting the system to single-user mode

• Running fsck(1M) on the mirror metadevice

• Remounting file system read-write

• Optional: running the metaroot(1M) command for a root (/) mirror

• Verifying that the /etc/vfstab file correctly references the metadevice for the file system entry

• Rebooting

Example -- Recovering the root (/) Mirror

In the following example, root (/) is mirrored with a two-way mirror, d0. The root (/) entry in /etc/vfstab has somehow reverted back to the original slice of the file system, but the information in /etc/system still shows booting to be from the mirror d0. The most likely reason is that the metaroot(1M) command was not used to maintain /etc/system and /etc/vfstab, or an old copy of /etc/vfstab was copied back.

The incorrect /etc/vfstab file would look something like the following:

#device        device          mount          FS      fsck   mount    mount
#to mount      to fsck         point          type    pass   at boot  options
#
/dev/dsk/c0t3d0s0 /dev/rdsk/c0t3d0s0  /       ufs      1     no       -
/dev/dsk/c0t3d0s1 -                   -       swap     -     no       -
/dev/dsk/c0t3d0s6 /dev/rdsk/c0t3d0s6  /usr    ufs      2     no       -
#
/proc             -                  /proc    proc     -     no       -
fd                -                  /dev/fd  fd       -     no       -
swap              -                  /tmp     tmpfs    -     yes      -

Because of the errors, you automatically go into single-user mode when the machine is booted:

ok boot
...
SunOS Release 5.5 Version Generic [UNIX(R) System V Release 4.0]
Copyright (c) 1983-1995, Sun Microsystems, Inc.
configuring network interfaces: le0.
Hostname: antero
mount: /dev/dsk/c0t3d0s0 is not this fstype.
setmnt: Cannot open /etc/mnttab for writing

INIT: Cannot create /var/adm/utmp or /var/adm/utmpx

INIT: failed write of utmpx entry:"  "

INIT: failed write of utmpx entry:"  "

INIT: SINGLE USER MODE

Type Ctrl-d to proceed with normal startup,
(or give root password for system maintenance): <root-password>

At this point, root (/) and /usr are mounted read-only. Follow these steps:

1. Run fsck(1M) on the root (/) mirror.

   ---

   Note -

   Be careful to use the correct metadevice for root.

   ---

   # fsck /dev/md/rdsk/d0 ** /dev/md/rdsk/d0 ** Currently Mounted on / ** Phase 1 - Check Blocks and Sizes ** Phase 2 - Check Pathnames ** Phase 3 - Check Connectivity ** Phase 4 - Check Reference Counts ** Phase 5 - Check Cyl groups 2274 files, 11815 used, 10302 free (158 frags, 1268 blocks, 0.7% fragmentation)

2. Remount root (/) read/write so you can edit the /etc/vfstab file.

   # mount -o rw,remount /dev/md/dsk/d0 / mount: warning: cannot lock temp file </etc/.mnt.lock>

3. Run the metaroot(1M) command.

   # metaroot d0

   This edits the /etc/system and /etc/vfstab files to specify that the root (/) file system is now on metadevice d0.

4. Verify that the /etc/vfstab file contains the correct metadevice entries.

   The root (/) entry in the /etc/vfstab file should appear as follows so that the entry for the file system correctly references the mirror:

   #device device mount FS fsck mount mount #to mount to fsck point type pass at boot options # /dev/md/dsk/d0 /dev/md/rdsk/d0 / ufs 1 no - /dev/dsk/c0t3d0s1 - - swap - no - /dev/dsk/c0t3d0s6 /dev/rdsk/c0t3d0s6 /usr ufs 2 no - # /proc - /proc proc - no - fd - /dev/fd fd - no - swap - /tmp tmpfs - yes -

5. Reboot.

   The system returns to normal operation.