Restore Data - AIX File System iDataAgent - Full System Restore

Topics | How To | Full System Restore | Related Topics

Overview

The difference between a normal restore and a full system restore is the severity of the problem. Normally, if data is lost or removed, it is recovered from the archives using the normal restore procedures. However, when a normal restore operation cannot correct a software and/or hardware corruption problem, some additional changes may be required.

When the root file system is lost, a full system restore is required.

A full system restore for AIX involves using the mksysb command.

mksysb Command

The mksysb command creates an installable image of the root volume group either in a file or onto a bootable tape. In essence, it creates a backup of the operating system (that is, the root volume group). You can use this backup to reinstall a system to its original state after it has been corrupted. If you create the backup on tape, the tape is bootable and includes the installation programs needed to install from the backup.

The file-system image is in backup-file format. The tape format includes a boot image, a bosinstall image, and an empty table of contents followed by the system backup (root volume group) image. The root volume group image is in backup-file format; this image includes data files and optional map files.

The mksysb command also creates the /bosinst.data file from the system default file if the /bosinst.data file does not exist.

The image that the mksysb command creates does not include data on raw devices or in user-defined paging spaces.

If you are using a system with a remote-mounted /usr file system, you cannot reinstall your system from a backup image.

The mksysb command may not restore all device configurations for special features, such as /dev/netbios and some device drivers not shipped with the product.

Some rspc systems do not support booting from tape. When you make a bootable mksysb image on an rspc system that does not support booting from tape, the mksysb command issues a warning indicating that the tape will not be bootable. You can install an mksysb image from a system that does not support booting from tape by booting from a CD and entering maintenance mode. In maintenance mode, you will be able to install the system backup from tape.

Command Syntax

The command syntax is as follows:

mksysb [ -b Number ] [ -e ] [ -p ] [ -v ] [ -X ] [ -i | -m ] Device | File

where:

-b Number is the number of 512-byte blocks to write in a single output operation.
-e excludes the files/directories.
-p prevents the files from being packed as they are backed up.
-v indicates verbose mode, which lists files as they are backed up.

This parameter applies only to AIX Version 4.2 or later.
-X automatically expands the /tmp file system if necessary. This file system may need to be extended to make room for the boot image when creating a bootable backup to tape.

This parameter applies only to AIX Version 4.2 or later.
-i creates the /image.data file.
-m creates the /image.data file and the physical partition map files.

You must include only one of the following two parameters; otherwise, the command will not work.
device is the name of the device to receive the backup information. (e.g., /dev/rmt0.1).
File is the name of the file to receive the backup information.

Back Up the Root Volume Group

To back up the root volume group:

At the prompt, enter the appropriate version of the mksysb command. Be sure to include the name of the appropriate device or file to which the backup information should be sent. For example:

# /usr/bin/mksysb -m -v -i -X -p /dev/rmt0.1
A series of messages similar to the following appears. A message indicating backup
completion should appear toward the end of this series.

   Creating information file (/image.data) for rootvg....
   Creating tape boot image............
   Creating list of files to back up....
   Backing up 61161 filesBacking up to /dev/rmt0.1.
   Cluster 51200 bytes (100 blocks).

   Volume 1 on /dev/rmt0.1

   a            8243        ./bosinst.data
   a            6178        ./image.data
   a             384        ./tmp/vgdata/rootvg/hd1.map
   a            1416        ./tmp/vgdata/rootvg/hd2.map

   The total size is 2459400240 bytes.

   Backup finished on Tue Sep 25 10:33:15 EDT 2001;
   there are 4822100 blocks on volumes.

   0512-003 mksysb may not have been able to archive some files.

   The messages displayed on the Standard Error contained additional
   information.

Perform a Full System Restore

Try to avoid the unconditional overwrite of the root directory on a live file system. This is a mechanism that allows an unconditional overwrite of open files in the root directory (/) on a live file system. Performing such a restore can result in an inconsistent system that may also fail to boot. Use this option AT YOUR OWN RISK.

Required Capability: Capabilities and Permitted Actions

To perform a full system restore:

Reboot the system, and quickly go to the next step.
As the system restarts, the console provides a series of POST messages. Before the last message (which is in audio), press F1 to bring up the SMS console.
From the SMS console, alter or modify the boot sequence to have the system boot from the tape drive containing the mksysb tape (i.e., the bootable tape created by the mksysb command).
Save the boot sequence and exit. The system should now boot from the tape.
Go to the CommCell Console. Then right-click the backup set, click All Tasks, click Restore, enter / as the path to restore from, and select "restore to same paths."

Do not select Unconditional Overwrite from the Restore Options dialog box.
When restoring encrypted data, refer to Data Encryption.
Click OK to start the restore.
Verify that the restore operation has completed successfully. Then reboot the computer. The system should boot to the newly-restored root.