By default, every directory in the filer's active file system contains a directory named .snapshot, through which users can access old versions of files in that directory. How users gain access to snapshots depends on the file-sharing protocol used--NFS or CIFS--and is described in the following sections. Access to snapshots can be turned off.
Snapshot files carry the same permissions as the original file. A user who has permission to read a file in the active file system can read that file in a snapshot. A user without read permission to the active file cannot read that file in a snapshot. Write permission does not apply because snapshots are read-only. Snapshots can be accessed by any user with the appropriate permissions.
The following illustration shows the directory structure on an NFS client with the vol0 volume of a filer named toaster mounted on the /n/toaster directory.
In this example, the user can obtain access to snapshots by way of the /n/toaster/.snapshot directory. Notice that the .snapshot directory is shown only at the mount point, although it actually exists in every directory in the tree. The user, however, can only see the .snapshot directory at the mount point. That is, the .snapshot directory is accessible by name in each directory, but is only seen in the output of the ls command at the mount point.
For example, at the mount point of a filer file system, a directory listing looks like this:
filerA> ls -a
. .. .snapshot dir1 dir2
The same command entered in a directory below the mount point does not show the .snapshot directory; for example:
filerA> cd dir1
filerA> ls -a
. .. file1 file2
If you enter the ls command with the directory name .snapshot, you can see a directory for each of the snapshots for the dir1 directory:
filerA> ls .snapshot
hourly.0 hourly.4 nightly.0 nightly.4
hourly.1 hourly.5 nightly.1 nightly.5
hourly.2 hourly.6 nightly.2 weekly.0
hourly.3 hourly.7 nightly.3 weekly.1
If the .snapshot directory entry appeared in every directory, it would cause many commands to work improperly. For instance, all recursive commands for deleting files would fail because everything below the .snapshot directory is read-only. Recursive copies would copy everything in the snapshots as well as files in the active file system, and a find command would generate a list much longer than expected.
To CIFS users, the .snapshot directory appears only at the root of a share. For example, if a user's home directory is a share named bill that corresponds to the /vol/vol0/home/bill directory, only the /vol/vol0/home/bill/.snapshot directory is visible. When this user displays the contents of the home directory, the .snapshot directory is displayed as ~snapshot if the operating system supports long file names and as ~SNAPSHT if the operating system supports only short file names.
Note
The .snapshot directory can be made visible in a directory listing or Windows Explorer display if the client operating system is configured to show hidden files.
In each directory within the share, a snapshot directory exists but is not visible to clients. For example, if the client operating system supports long file names, the applications on that operating system can use the snapshot at each level of the share by using .snapshot, ~snapshot, or ~SNAPSHT as the directory name. The user cannot, however, display the directory name in any listing.
To access snapshots on Windows NT 4 or other Windows® clients (Windows 95 or later), complete the following step.
| 1 | From the Start > Run menu, enter the following command: \\filername\share\.snapshot (or ~snapshot or ~SNAPSHT). |
\\filerA\home\.snapshot
Snapshots can also be accessed lower in the share by providing a path to a lower directory. Snapshots can be accessed through DOS on any system by changing to the ~SNAPSHT directory.
Sometimes you might want to disable and enable client access to snapshots in a specific volume, for example, for security reasons or to prevent access to corrupted or virus-infected files.
To disable or enable client access to snapshots in a volume, complete the following step.
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Part No. 210-00325
File: snap3.htm
Last updated: 01/14/03 17:50:33