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
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:
Run fsck(1M) on the root (/) mirror.
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) |
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> |
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.
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 - |
Reboot.
The system returns to normal operation.