Troubleshooting Booting Problems

If a system fails to start correctly in multiuser mode, it’s likely that one of the scripts being run in /etc/rc2.d is the cause. In order to prevent the system from going multiuser, it is possible to boot directly into single-user mode from the ok prompt:

ok boot –s
...
INIT: SINGLE USER MODE
Type Ctrl-d to proceed with normal startup,
(or give root password for system maintenance):

At this point, the root password can be entered, and the user will be given a root shell. However, not all file systems will be mounted, although individual scripts can then be checked individually for misbehaving applications.

If the system will not boot into single-user mode, the solution is more complicated because the default boot device cannot be used. For example, if an invalid entry has been made in the /etc/passwd file for the root user, the system will not boot into single- or multiuser mode. To recover the installed system, the host needs to be booted from the installation CD-ROM into single-user mode. At this point, the default root file system can be mounted on a separate mount point, the /etc/passwd file edited, and the system rebooted with the default boot device. This sequence of steps is shown next, assuming that /etc is located on /dev/dsk/c0t0d0s1:

ok boot cdrom
...
INIT: SINGLE USER MODE
Type Ctrl-d to proceed with normal startup,
(or give root password for system maintenance):
# mkdir /temp
# mount /dev/dsk/c0t0d0s1 /temp
# vi /temp/etc/passwd
# sync; init 6