Chapter 8. System Backup and Restore

8.1 Saving Information

Data in AIX is divided in system and user parts. System data makes up the operating system and its extensions. It is kept in the root file system on root volume group. User data is mainly contained in user-defined file systems, but partly contained in root file system (/home file system).

In order to successfully backup your system to ensure availability of data at all times. AIX provides you with a number of commands to achieve this task. These commands are used depending on the type of information you are trying to save. Figure 99 shows you the flow of the backup process, for example, in order to save rootvg you can adopt different approaches depending on what are you trying to save using the mksysb command. You can alternatively save individual files by using tar, cpio, dd and backup commands. You can also save entire user volume groups by using the savevg command.

The format of the mksysb tape that is produced is given in section 8.2 The Data Layout of a mksysb Tape.

Note

Keep following points in mind while running the mksysb command: Use /etc/exclude.rootvg file to exclude any file, file system, directory or patterns that you do not need in your backup. Use the -e flag with the mksysb command to use the exclude.rootvg file. /tmp is used as a work area by the mksysb command. It typically needs 8 - 12 MB of free space in /tmp. Use the -X flag with mksysb to automatically expand the /tmp file system, otherwise you will encounter an error similar to: 0511-432 A write error occurred: There is not enough space in the file system. and mksysb will fail. Use the -p flag (disable software packing of backup) only if you know that your tape drive does not do compression.

Figure 99 summarizes the methods used to back up system and user data.



Figure 99: Saving Information

8.2 The Data Layout of a mksysb Tape