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AIX Version 4.3 System Management Guide: Operating System and Devices

Backing Up the System Image and User-Defined Volume Groups

A backup image serves two purposes. One is to restore a corrupted system using the system's own backup image. The other is to transfer installed and configured software from one system to others. You can backup the system or volume groups using Web-based System Manager, SMIT, or command procedures.

The rootvg volume group is a hard disk, or group of disks, containing start up files, the Base Operating System (BOS), configuration information, and any optional software products. A user-defined volume group (also called nonrootvg volume group) typically contains data files and application software.

The Web-based System Manager and SMIT procedures use the mksysb command to create a backup image that can be stored either on tape or in a file. If you choose tape, the backup program writes a boot image to the tape, which makes it suitable for installing.

  1. Bootable tapes cannot be made on or used to boot a PowerPC Personal Computer.
  2. If you choose the SMIT method for backup, you must first install the sysbr fileset in the bos.sysmgt software package. See Installing Optional Software and Service Updates in the AIX Installation Guide for information on how to install software packages and options.

Configuring before the Backup

Configure the source system before creating a backup image of it. If, however, you plan to use a backup image for installing other, differently configured target systems, create the image before configuring the source system.

The source system is the system from which you created the backup copy. The target system is the system on which you are installing the backup copy.

The installation program automatically installs only the device support required for the hardware configuration of the installed machine. Therefore, if you are using a system backup to install other machines, you may need to install additional devices on the source system before making the backup image and using it to install one or more target systems.

Use the Web-based System Manager fast path, wsm devices,SMIT fast path, smit devinst, to install additional device support on the source system.

For information on installing optional software, see "Installing Optional Software and Service Updates" in the AIX Installation Guide.

A backup transfers the following configurations from the source system to the target system:

Refer to the section on customizing the BOS install program "Customizing the BOS Install Program" in the AIX Installation Guide for information about how to set installation parameters to enable you to bypass menu prompts when you install the target machine from a system backup.

Mounting and Unmounting File Systems

The "Backing Up Your System" procedure backs up only mounted file systems in the rootvg volume group. You must, therefore, mount all file systems you want to back up before starting. Similarly, you must unmount file systems you do not want backed up.

This backup procedure backs up files twice if a local directory is mounted over another local directory in the same file system. For example, if you mount /tmp over /usr/tmp, the files in the /tmp directory will be backed up twice. This duplication might exceed the number of files a file system can hold, which can cause a future installation of the backup image to fail.

Security Considerations

If you install the backup image on other systems, you might not, for security reasons, want passwords and network addresses copied to the target systems. Also, copying network addresses to a target system creates duplicate addresses that can disrupt network communications.

Backing Up Your System

The following procedures describe how to make an installable image of your system.


Before backing up the rootvg volume group:

Before backing up a user-defined volume group:

Backing Up Your System Tasks
Web-based System Manager:    wsm backup fast path
(Backups application)

Task SMIT Fast Path Command or File
Backing up the rootvg volume group
  1. Log in as root.
  2. Mount file systems for backup.1
    smit mountfs
  3. Unmount any local directories that are mounted over another local directory.
    smit umountfs
  4. Make at least 8.8MB of free disk space available in the /tmp directory.2
  5. Back up.
    smit mksysb
  6. Write-protect the backup media.
  7. Record any backed-up root and user passwords.
  1. Log in as root.
  2. Mount file systems for backup.1
    See mount command.
  3. Unmount any local directories that are mounted over another local directory.
    See umount command.
  4. Make at least 8.8MB of free disk space available in the /tmp directory.2
  5. Back up.
    See mksysb command.
  6. Write-protect the backup media.
  7. Record any backed-up root and user passwords.
Verify a Backup Tape3 smit lsmksysb  
Backing up a user-defined volume group4 smit savevg
  1. Modify the file system size before backing up, if necessary.5
    mkvgdata VGName
    then edit
  2. Save the volume group.
    savevg command.
  1. The mksysb command does not back up file systems mounted across an NFS network.
  2. The mksysb command requires this working space for the duration of the backup. Use the df command, which reports in units of 512-byte blocks, to determine the free space in the /tmp directory. Use the chfs command to change the size of the file system, if necessary.
  3. This procedure lists the contents of a mksysb backup tape. The contents list verifies most of the information on the tape but does not verify that the tape can be booted for installations. The only way to verify that the boot image on a mksysb tape functions properly is by booting from the tape.
  4. If you want to exclude files in a user-defined volume group from the backup image, create a file named /etc/exclude.volume_group_name, where volume_group_name is the name of the volume group that you want to back up. Then edit /etc/exclude.volume_group_name and enter the patterns of file names that you do not want included in your backup image. The patterns in this file are input to the pattern matching conventions of the grep command to determine which files will be excluded from the backup.
  5. If you choose to modify the VGName.data file to alter the size of a file system, you must not specify the -i flag or the -m flag with the savevg command, since the VGName.data file will be overwritten.


Restoring a Backup Image

When installing the backup image, the system checks whether the target system has enough disk space to create all the logical volumes stored on the backup. If there is enough space, the entire backup is recovered. Otherwise, the installation halts and the system prompts you to choose more destination hard disks.

File systems created on the target system will be the same size as they were on the source system, unless the SHRINK variable was set to yes in the image.data file before the backup image was made. An exception is the /tmp directory, which can be increased to allocate enough space for the bosboot command. For information about setting variables, refer to the image.data file in AIX Version 4.3 Files Reference.

When it finishes installing the backup image, the installation program reconfigures the Object Data Manager (ODM) on the target system. If the target system does not have exactly the same hardware configuration as the source system, the program may modify device attributes in the following target system files:

For more information about installing (or restoring) a backup image, see Installing BOS from a System Backup in the AIX Installation Guide.

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