1.\" 2.\" Copyright (c) 2003 Networks Associates Technology, Inc. 3.\" All rights reserved. 4.\" 5.\" This software was developed for the FreeBSD Project by Marshall 6.\" Kirk McKusick and Network Associates Laboratories, the Security 7.\" Research Division of Network Associates, Inc. under DARPA/SPAWAR 8.\" contract N66001-01-C-8035 ("CBOSS"), as part of the DARPA CHATS 9.\" research program. 10.\" 11.\" Redistribution and use in source and binary forms, with or without 12.\" modification, are permitted provided that the following conditions 13.\" are met: 14.\" 1. Redistributions of source code must retain the above copyright 15.\" notice, this list of conditions and the following disclaimer. 16.\" 2. Redistributions in binary form must reproduce the above copyright 17.\" notice, this list of conditions and the following disclaimer in the 18.\" documentation and/or other materials provided with the distribution. 19.\" 3. The names of the authors may not be used to endorse or promote 20.\" products derived from this software without specific prior written 21.\" permission. 22.\" 23.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 24.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 27.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33.\" SUCH DAMAGE. 34.\" 35.Dd May 22, 2023 36.Dt MKSNAP_FFS 8 37.Os 38.Sh NAME 39.Nm mksnap_ffs 40.Nd take a file system snapshot 41.Sh SYNOPSIS 42.Nm 43.Ar snapshot_name 44.Sh DESCRIPTION 45The 46.Nm 47utility creates a snapshot named 48.Ar snapshot_name . 49This name is a path in the file system to be snapshotted. 50Typically this is under the 51.Pa .snap 52directory in the root of the file system, but it can 53be anywhere in the filesystem being snapshotted. 54Snapshots can be listed using the 55.Xr snapinfo 8 56command. 57.Pp 58After a snapshot is taken it appears as a file. 59The size of the snapshot file is equal to the size of the 60file system from which it was taken. 61It can be moved, renamed or deleted (which removes the snapshot). 62.Pp 63The group ownership of the file is set to 64.Dq Li operator ; 65the owner of the file remains 66.Dq Li root . 67The mode of the snapshot is set to be readable by the owner 68or members of the 69.Dq Li operator 70group. 71.Sh EXAMPLES 72Create a snapshot of 73.Pa /home 74file system and mount the snapshot elsewhere: 75.Bd -literal -offset indent 76mksnap_ffs /home/.snap/snap1 77mdconfig -a -t vnode -o readonly -f /home/.snap/snap1 78mount -o ro /dev/md0 /mnt/ 79.Ed 80.Pp 81Delete a snapshot: 82.Bd -literal -offset indent 83rm /home/.snap/snap1 84.Ed 85.Sh SEE ALSO 86.Xr rm 1 , 87.Xr chmod 2 , 88.Xr chown 8 , 89.Xr mdconfig 8 , 90.Xr mount 8 , 91.Xr snapinfo 8 92.Sh HISTORY 93The 94.Nm 95utility first appeared in 96.Fx 5.1 . 97.Sh CAVEATS 98The disk full situation is not handled gracefully and may 99lead to a system panic when no free blocks are found. 100.Pp 101Every filesystem can have only up to 20 active snapshots. 102When this limit is reached, attempting to create more snapshots 103fails with 104.Er ENOSPC , 105and 106.Nm 107reports that it is 108.Dq out of space . 109