Backups

In general, backups of user and system data are kept in case the data is accidentally removed or if there is a disk failure. It is easier to manage backups when user data is kept separate from system data.

The following are reasons for keeping system data separate from user data:

• User data tends to change much more often than operating system data. Backup images are much smaller if the system data is not backed up into the same image as the user data. The number of users affects the storage media and frequency that is required for backup.
• It is quicker and easier to restore user data when it is kept separate. Restoring the operating system along with the user data requires extra time and effort. The reason is that the method that is used to recover the operating system data involves starting the system from removable media (tape or CD) and installing the system backup.

To back up the system data, unmount all user file systems, including /home with the umount command. If these file systems are in use, you cannot unmount them. Schedule the backups at low usage times so they can be unmounted; if the user data file systems remain mounted, they are backed up along with the operating system data. Use the mount command to ensure that only the operating system file systems are mounted.

node  mounted  mounted over vfs       date         options

      /dev/hd4     /        jfs   Jun 11 10:36  rw,log=/dev/hd8

      /dev/hd2     /usr     jfs   Jun 11 10:36  rw,log=/dev/hd8

      /dev/hd9var  /var     jfs   Jun 11 10:36  rw,log=/dev/hd8

      /dev/hd      /tmp     jfs   Jun 11 10:36  rw,log=/dev/hd8

After you are certain that all user file systems are unmounted, you are now ready to back up the operating system data.

When you finish backing up the operating system, mount the user file system by using the smit mount command. Next, you can back up files, file systems, or other volume groups, depending on your needs.