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AIX Version 4.3 Installation Guide

Introduction to Backing Up Your System

A backup image serves two purposes. One is to have a working copy of your system in case your system becomes corrupted. The other is to transfer installed and configured software from one system to others. You can use the Web-based System Manager Backups application or the SMIT Back Up the System menu to make a backup image of the root volume group. Use the Web-based System Manager Volumes application or the SMIT Save a Volume Group menu to make a backup image of user volume groups.

The root volume group is a hard disk, or group of disks, containing start up files, BOS, configuration information, and any optional software products. A user volume group (also called nonroot volume group) typically contains data files and application software.

The Web-based System Manager Backups application and the SMIT Back Up the System menu both use the mksysb command to create a backup image, stored either on tape or in a file. If you choose tape, the backup program by default writes a boot image to the tape, which makes it suitable for installing.

Configuring before the Backup

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.

Configure the source system before creating a backup image of it if you want the source and target to be identical. If, however, you plan to use a backup image for installing other, differently configured target systems, create the image before configuring the source system, or set the RECOVER_DEVICES variable to no in the bosinst.data file. Refer to "Customizing the BOS Install Program" for more information about the bosinst.data file.

The installation program automatically installs only the device support required for the hardware configuration of the source system. Therefore, if you are using a system backup to install other machines, install additional devices on the source system before making the backup image and using this backup image to install one or more target systems, or boot the target system from a product media, then use the mksysb tape to install the target system. Any additional device support required on the target system is automatically installed after the mksysb image is restored. For further information, refer to "Cloning Considerations".

To install additional device support on the source system, use the Web-based System Manager Devices application or the Install Additional Device Software SMIT menu option.

For information on installing optional software, see "Installing Optional Software and Service Updates".

Refer to "Customizing the BOS Install Program" 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.

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.

Using the Web-based System Manager Backups application or the SMIT backup menu lets you preserve configuration information, thus avoiding some of the configuring tasks normally required after restoring a system backup. A backup preserves the configuration if:

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

Mounting and Unmounting File Systems

The procedure in this chapter backs up only mounted file systems in the root 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, or you must use the /etc/exclude.rootvg file to list files you do not want backed up. See "Backing Up Your System" in the AIX Version 4.3 System Management Guide: Operating System and Devices for more information.

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.

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."

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