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System Management Concepts: 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 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. Startup tapes cannot be made on or used to start 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 Using SMIT in the AIX 5L Version 5.1 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 might 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 Web-based System Manager (type wsm, then select Network), or the 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 Using SMIT in the AIX 5L Version 5.1 Installation Guide.

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

See the section on customizing the BOS install program Customizing the BOS Install Program in the AIX 5L Version 5.1 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 are 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.

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 are 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, see the image.data file in AIX 5L Version 5.1 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 might 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 5L Version 5.1 Installation Guide.

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