Some typical causes of an LED 551, 555, or 557 during an IPL are:

a corrupted file system
a corrupted journaled file system (JFS) log device
a failing fsck (file system check) caused by a bad file system helper
a bad disk in the machine that is a member of the rootvg

To diagnose and fix these typical problems, you must boot from bootable media and run fsck to fix any file systems that may be corrupted.
If fsck fails when calling logredo then run logform on /dev/hd8.

WARNING: Do not use this document if the system is a /usr client, diskless client, or dataless client.

1. Power down your system. If it has a key mode select switch (that is, if it is a Microchannel-based system), turn the key to the Service position.

2. With bootable media of the same version and technology level as the system, boot the system.

The bootable media can be any one of the following:
Bootable CD-ROM
Bootable Install Tape

Follow the screen prompts to the following menu:

Welcome to Base Operating System
Installation and Maintenance

3. Choose Start Maintenance Mode for System Recovery (Option 3). The next screen has the Maintenance Menu.

Choose Access a Root Volume Group (Option 1).

The next screen displays a warning that indicates you will not be able to return to the Base OS menu without rebooting.

Choose 0 continue.

The next screen displays information about all volume groups on the system.

Select the root volume group by number.

Choose Access this volume group and start a shell before mounting the filesystems (Option 2).

If you get errors indicating that a physical volume is missing from the rootvg, run diagnostics on the physical volumes to find out if you have a bad disk. Do not continue with the rest of the steps in this document.

If you get other errors from the preceding option, do not continue with the rest of the steps in this document. Correct the problem causing the error. If you need assistance correcting the problem, contact one of the following:
your local branch office
your point of sale
your AIX support center
4. Next, run the following commands to check and repair file systems. (The -y option gives fsck permission to repair file systems when necessary.)

fsck -y /dev/hd1
fsck -y /dev/hd2
fsck -y /dev/hd3
fsck -y /dev/hd4
fsck -y /dev/hd9var

5. If fsck fails during the logredo phase, you will have to format the default jfslog (or j2fslog) for the rootvg JFS (or JFS2) file systems.

/usr/sbin/logform /dev/hd8

Answer yes when asked if you want to destroy the log.

6. Type exit. The file systems will automatically mount after you type exit.

7. If you are running the Andrew File System (AFS), use the following commands to find out whether you have more than one version of the v3fshelper file. Otherwise, skip to step 8.

cd /sbin/helpers
ls -l v3fshelper*

If you have only one version of the v3fshelper file (for example, v3fshelper), proceed to step 8.

If there is a version of v3fshelper marked as original (for example, v3fshelper.orig), run the following commands:

copy v3fshelper v3fshelper.afs
copy v3fshelper.orig v3fshelper

8. Determine which disk is the boot disk with the lslv command. The boot disk will be shown in the PV1 column of the lslv output.

lslv -m hd5

WARNING: Do not proceed further if the system is a /usr client, diskless client, or dataless client.

9. Recreate the boot image and alter the boot list. (hdisk# is the boot disk determined in step 9.)

bosboot -a -d /dev/ipldevice
bootlist -m normal <hdisk#>

10. If you copied the v3fshelper file in step 7, copy AFS file system helper back to v3fshelper:

copy v3fshelper.afs v3fshelper

11. With the key in Normal position, run

shutdown -Fr

If you followed all of the preceding steps and the system still stops at an LED 551, 555, or 557 during a reboot in Normal mode, you may want to consider reinstalling your system from a recent backup.
Isolating the cause of the hang could be excessively time-consuming and may not be cost-effective in your operating environment.

To isolate the possible cause of the hang would require a debug boot of the system.
Instructions for doing this are included in the document “Capturing Boot Debug”, available at

It is still possible, in the end, that isolation of the problem may indicate a restore or reinstall of AIX is necessary to correct it.