freebsd man page for mksnap_ffs

MKSNAP_FFS(8)						    BSD System Manager's Manual 					     MKSNAP_FFS(8)

NAME
     mksnap_ffs -- take a file system snapshot

SYNOPSIS
     mksnap_ffs snapshot_name

DESCRIPTION
     The mksnap_ffs utility creates a snapshot named snapshot_name.

     The group ownership of the file is set to ``operator''; the owner of the file remains ``root''.  The mode of the snapshot is set to be read-
     able by the owner or members of the ``operator'' group.

EXAMPLES
     Create a snapshot of /usr/home file system and mount the snapshot elsewhere:

	   mksnap_ffs /usr/home/snapshot
	   mdconfig -a -t vnode -o readonly -f /usr/home/snapshot
	   mount -o ro /dev/md0 /mnt/

SEE ALSO
     chmod(2), chown(8), mdconfig(8), mount(8)

HISTORY
     The mksnap_ffs utility first appeared in FreeBSD 5.0.

CAVEATS
     The disk full situation is not handled gracefully and may lead to a system panic when no free blocks are found.

     Every filesystem can have only up to 20 active snapshots.	When this limit is reached, attempting to create more snapshots fails with ENOSPC,
     and mksnap_ffs reports that it is ``out of space''.

BSD
								 February 14, 2011							       BSD