Troubleshooting an Installation from a System Backup

AIX Version 4.3 Installation Guide

Troubleshooting an Installation from a System Backup

This section describes solutions for common problems when installing from a system image created with the mksysb command.

The section discusses the following topics:

Bootup Failure

If a backup tape fails to boot, you can still install using a mksysb image stored on the tape.

Boot the machine from Volume 1 of the AIX product media, then install the backup from Maintenance mode. Refer to Installing BOS from CD-ROM or Tape for instructions on booting from product media. Follow the instructions to the point when the Welcome to the Base Operating System Installation and Maintenance screen is displayed.

Booting from the Product CD-ROM

Complete the following steps when the Welcome screen is displayed:

Choose the Start Maintenance Mode for System Recovery option.
The Maintenance screen is displayed.
Choose the Install from a System Backup option.
The Choose Tape Drive screen is displayed.
Choose the drive containing the backup tape.
The system reads the tape and begins the installation.
Do not remove the CD from the CD-ROM drive.
The system reads the kernel and device support required on the target system from the CD.
Return to step 7 in To Install BOS from a System Backup and continue the instructions for installing the backup.
Note: The Use Maps option is not supported in Maintenance Mode. The section Prompted Installation includes a description of the use of maps on disks selected in the System Backup Installation and Settings screen.

Booting from the Product Tape

Create a diskette that contains a ./signature file that contains the characters 'data' and a ./bosinst.data file with SWITCH_TO_PRODUCT_TAPE = yes in the control_flow stanza. See Customizing the BOS Install Program for information on creating these files.
Insert the diskette that you created in step 1 into the diskette drive.
Boot the system from Volume 1 of the product tape.
Choose the Start Maintenance Mode for System Recovery option when the Welcome screen is displayed.
The Maintenance screen is displayed.
Choose the Install from a System Backup option.
Remove the product tape from the tape drive and insert the mksysb tape.
The Choose Tape Drive screen is displayed.
Choose the drive containing the backup tape.
The system reads the tape and begins the installation.

Note: The system will prompt you to remove the mksysb tape and insert the product tape after the mksysb backup has been restored.
Return to step 7 in To Install BOS from a System Backup and continue the instructions for installing the backup.
Note: The Use Maps option is not supported in Maintenance Mode. The section Prompted Installation includes a description of the use of maps on disks selected in the System Backup Installation and Settings screen.

mksysb Image Configuration on System Backup Tapes

General Information Regarding mksysb System Backups

Bootable mksysb tapes are made up of four images, the boot image, the BOS Install/Maintenance image, the toc image and the system backup image. The system backup image, is the actual backup of the files in the rootvg in all jfs mounted filesystems.

The first three images are required to be created with a tape block_size value of 512. The mksysb command assures that the block size is 512 when these images are created. There are no restrictions on the block size used for the fourth (system backup image) on the tape, in AIX Version 4.3.2 or later. In previous versions, the block size would be changed to 512 for the fourth image, if the original system block size was less than 512. At the end of the mksysb tape creation, it was reset to the original value.

It is required that the value of the block size be saved in the /tapeblksz file in the second image on the tape. The second and fourth images are stored in backup/restore format. Again, mksysb assures the correctness of the tapes created using the mksysbcommand.

If there are problems with the bosinst.data file, the image.data file, or the tapeblksz file, they can be restored from the second image on the tape and checked. These files as well as commands necessary for execution in the RAM filesystem (when running in maintenance mode after booting from the tape) are stored in the second image.

Restoring a File from the Second Image Type

To restore a file from the second image follow these steps:

Be sure the tape block size is 512 by entering the following command:
```
# lsattr -E -l rmt0
```
If the block size is not correct, use the following command to set it to 512:
```
# chdev -l rmt0 -a block_size=512
```
Make sure the tape is rewound. If the tape is not rewound, enter the following command:
```
# tctl -f /dev/rmt0 rewind
```
Extract the necessary files by entering:
```
# restore -xvq -s2 -f /dev/rmt0.1 .filename
```
Note: The filename should be the full path, and always preceded with a . (dot character), such as ./tapeblksz.
Rewind the tape by entering:
```
# tctl -f /dev/rmt0 rewind
```

Source and Target Differences

Consider the differences in the source and target systems when planning an installation from a mksysb backup.

The original system image made with the mksysb command might not match your present configuration. For example, if you changed devices after backing up your system, the original source image does not have the correct device drivers for the target system. Avoid system inequalities such as different communication adapters, TTY attributes, and printer attributes. If you are using the Common Desktop Environment (CDE) on the target system, make all configuration changes, then shutdown and reboot the system before you start CDE.

The same suggestion applies when using a backup image to install additional systems. First configure the source system with drivers required for the target, then create the backup.

Suggestions for Reported Problems

The following troubleshooting tips apply to reported problems with installations from a mksysb image:

Check that you have sufficient free blocks in the file systems to write temporary files.
Check that each file system has at least 500 blocks free when the mksysb backup image is made. The system will need some work space in each file system when installing from a mksysb backup image.
Check that you are using the correct tape type for the density setting selected.
Check that the tape is not write protected.
Clean the tape drive at the recommended intervals and use only approved data-grade tapes (not video tapes for 8 mm).
7206 4-mm Digital Audio Tape (DAT) tape drives use only DAT tapes marked with the Dataphone Digital Services (DDS) symbol. Any other DAT tapes (for example, voice grade) will not work.
Check the /smit.log file for any errors from SMIT.
Check that your mksysb backup image contains an image.data file. If you create the mksysb backup image through Web-based System Manager or SMIT, it is done automatically. If you run mksysb from the command line, you must either run the mkszfile command first, or use the -i flag with the mksysb command.