IBM RS/6000 - Manual (Page 205)

2. Select the option to access the root volume group, and start a shell before the
filesystems are mounted.
3. Check the root volume group filesystems:
fsck -y /dev/hd1
fsck -y /dev/hd2
fsck -y /dev/hd3
fsck -y /dev/hd4
fsck -y /dev/hd9var
4. Format the Journaled File System (JFS) log:
logform /dev/hd8
Answer YES when asked if you want to destroy the log.
5. Type exit to mount the root filesystems.
6. Check the inittab file for any entries which may be causing problems.
7. Check for any full filesystems (particularly /, /tmp, /var and /usr).
8. Check the following files for any modification or problems with permissions:
/.profile
/etc/environment
/etc/profile
In addition, check that the files can be executed without problems, for example:
/usr/bin/sh /etc/environment
9. Recreate the bootimage:
bosboot -a -d /dev/hdiskx
Where hdiskx is the hard disk containing the boot logical volume. You can
determine which disk has the boot logical volume by running:
lslv -m hd5
The boot disk will be shown in the PV1 column.
If after trying the above the problem persists, then either contact your support
organization or restore from a system backup.
10.2.3 Recovering a System with no Bootable Media
If your system hangs during the AIX boot process, you can use the CD-ROM or
tape drive to boot into Maintenance mode using suitable media. If your system
hangs and you don't have media, then you can still gain access to a limited
maintenance shell.
By using the hardware diagnostics on the hard drive, you can access an AIX shell
which will allow you access to the filesystems in the system. The filesystems will,
however, be mounted so you will be unable to run
fsck . From this shell, you can
edit inittab or do whatever else is necessary and possible to fix the problem. To
access the shell, perform the following:
1. Turn on the RS/6000.
2. Press F5 during the firmware boot-up sequence (or 5 on an ASCII terminal) to
enter Service mode.
3. If diagnostics loads, select Service Aids.
Chapter 10. Troubleshooting 181