GPFS: Administration and Programming Reference - IRA Home

mmcrsnapshot Command
Options
NONE
If you do not want traverse the file system’s root to access the snapshot, a more convenient
mechanism that enables a connection in each directory of the active file system can be enabled
with the -a option of the mmsnapdir command.
Exit status
0 Successful completion.
nonzero A failure has occurred.
Security
You must have root authority to run the mmcrsnapshot command.
You may issue the mmcrsnapshot command from any node in the GPFS cluster.
When using the rcp and rsh commands for remote communication, a properly configured .rhosts file must
exist in the root user’s home directory on each node in the GPFS cluster. If you have designated the use
of a different remote communication program on either the mmcrcluster or the mmchcluster command,
you must ensure:
1. Proper authorization is granted to all nodes in the GPFS cluster.
2. The nodes in the GPFS cluster can communicate without the use of a password, and without any
extraneous messages.
Examples
To create a snapshot snap1, for the file system fs1, issue this command:
mmcrsnapshot fs1 snap1
The output is similar to this:
Writing dirty data to disk
Quiescing all file system operations
Writing dirty data to disk again
Creating snapshot.
Resuming operations.
Before issuing the command, the directory structure would appear similar to:
/fs1/file1
/fs1/userA/file2
/fs1/userA/file3
After the command has been issued, the directory structure would appear similar to:
/fs1/file1
/fs1/userA/file2
/fs1/userA/file3
/fs1/.snapshots/snap1/file1
/fs1/.snapshots/snap1/userA/file2
/fs1/.snapshots/snap1/userA/file3
If a second snapshot were to be created at a later time, the first snapshot would remain as is. Snapshots
are made only of active file systems, not existing snapshots. For example:
mmcrsnapshot fs1 snap2
132 GPFS: Administration and Programming Reference