When you use the fssnap command to create a UFS snapshot, observe how much disk space the backing-store file consumes. The backing-store file uses no space, and then it grows quickly, especially on heavily used systems. Make sure the backing-store file has enough space to grow, or limit its size with the -o maxsize=n [k,m,g] option, where n [k,m,g] is the maximum size of the backing-store file.
If the backing-store file runs out of space, the snapshot might delete itself, which causes the backup to fail. Check the /var/adm/messages file for possible snapshot errors.
For more information, see fssnap_ufs(1M).
Become superuser or assume an equivalent role.
Make sure that the file system has enough disk space for the backing-store file.
# df -k |
Make sure that a backing-store file of the same name and location does not already exist.
# ls /backing-store-file |
Create the UFS snapshot.
# fssnap -F ufs -o bs=/backing-store-file /file-system |
The backing-store file must reside on a different file system than the file system that is being snapshot.
Verify that the snapshot has been created.
# /usr/lib/fs/ufs/fssnap -i /file-system |
The following example shows how to create a snapshot of the /usr file system. The backing-store file is /scratch/usr.back.file, and the virtual device is /dev/fssnap/1.
# fssnap -F ufs -o bs=/scratch/usr.back.file /usr /dev/fssnap/1 |
The following example shows how to limit the backing-store file to 500 Mbytes.
# fssnap -F ufs -o maxsize=500m,bs=/scratch/usr.back.file /export/home /dev/fssnap/1 |
You can display the current snapshots on the system by using the fssnap -i option. If you specify a file system, you see detailed information about that snapshot. If you don't specify a file system, you see information about all of the current UFS snapshots and their corresponding virtual devices.
Use the UFS file system-specific fssnap command to view the extended snapshot information as shown in the following examples.
Become superuser or assume an equivalent role.
List current snapshots.
# /usr/lib/fs/ufs/fssnap -i Snapshot number : 0 Block Device : /dev/fssnap/0 Raw Device : /dev/rfssnap/0 Mount point : /export/home Device state : idle Backing store path : /var/tmp/bs.file Backing store size : 0 KB Maximum backing store size : Unlimited Snapshot create time : Wed Aug 29 15:22:06 2001 Copy-on-write granularity : 32 KB |
To display detailed information about a specific snapshot, use the following:
# /usr/lib/fs/ufs/fssnap -i /usr Snapshot number : 0 Block Device : /dev/fssnap/0 Raw Device : /dev/rfssnap/0 Mount point : /usr Device state : idle Backing store path : /var/tmp/bs.file Backing store size : 0 KB Maximum backing store size : Unlimited Snapshot create time : Wed Aug 29 15:23:35 2001 Copy-on-write granularity : 32 KB |
When you create a UFS snapshot, you can specify that the backing-store file is unlinked, which means that the backing-store file is removed after the snapshot is deleted. If you don't specify the -o unlink option when you create a UFS snapshot, you will have to delete it manually.
The backing-store file occupies disk space until the snapshot is deleted, whether you use the -o unlink option to remove the backing-store file or you remove it manually.
You can delete a snapshot either by rebooting the system or by using the fssnap -d command and specifying the path of the file system that contains the UFS snapshot.
Become superuser or assume an equivalent role.
Identify the snapshot to be deleted.
# /usr/lib/fs/ufs/fssnap -i |
Delete the snapshot.
# fssnap -d /file-system Deleted snapshot 1. |
(Optional) If you did not use the -o unlink option when you created the snapshot, you need to delete the backing-store file manually.
# rm /file-system/backing-store-file |
The following example shows how to delete a snapshot and assumes that the unlink option was not used.
# fssnap -i 0 / 1 /usr # fssnap -d /usr Deleted snapshot 1. # rm /scratch/usr.back.file |