Making and backing up an external snapshot of a JFS2

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You can make a snapshot of a mounted JFS2 that establishes a consistent block-level image of the file system at a point in time.

The snapshot image remains stable even as the file system that was used to create the snapshot, called the snappedFS, continues to change. The snapshot retains the same security permissions as the snappedFS had when the snapshot was made.

In the following scenario, you use the backsnap command to create an external snapshot and back up the snapshot to removable media without un mounting or quiescing the file system. You can also use the snapshot for other purposes, such as accessing the files or directories as they existed when the snapshot was taken. You can do the various snapshot procedures using SMIT, or the backsnap and snapshot commands.

To create an external snapshot of the /home/abc/test file system and back it up, by name, to the /dev/rmt0 tape device, run the following command:

backsnap -m /tmp/snapshot -s size=16M -if/dev/rmt0 /home/abc/test

The previous command creates a logical volume of 16 MB for the snapshot of the /home/abc/test JFS2 file system. The snapshot is mounted on the /tmp/snapshot directory and then a backup of the snapshot, by name, is made to the tape device. After the backup is complete, the snapshot is unmounted but remains available. Use the -R flag with the backsnap command if you want the snapshot removed when the backup is completed.