.\" Copyright (c) 2003 Networks Associates Technology, Inc.
.\" All rights reserved.
.\" This software was developed for the FreeBSD Project by Marshall
.\" Kirk McKusick and Network Associates Laboratories, the Security
.\" Research Division of Network Associates, Inc. under DARPA/SPAWAR
.\" contract N66001-01-C-8035 ("CBOSS"), as part of the DARPA CHATS
.\" research program.
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
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.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
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.\" 3. The names of the authors may not be used to endorse or promote
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.Dd October 3, 2016
.Dt MKSNAP_FFS 8
.Nd take a file system snapshot
utility creates a snapshot named
.Ar snapshot_name .
The group ownership of the file is set to
.Dq Li operator ;
the owner of the file remains
.Dq Li root .
The mode of the snapshot is set to be readable by the owner
or members of the
.Dq Li operator
Create a snapshot of
file system and mount the snapshot elsewhere:
.Bd -literal -offset indent
mdconfig -a -t vnode -o readonly -f /usr/home/snapshot
mount -o ro /dev/md0 /mnt/
.Sh SEE ALSO
.Xr chmod 2 ,
.Xr chown 8 ,
.Xr mdconfig 8 ,
.Xr mount 8
utility first appeared in
.Fx 5.1 .
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
.Er ENOSPC ,
reports that it is
.Dq out of space .