.\"
.\" 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.
.\"
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.Dd March 5, 2023
.Dt MKSNAP_FFS 8
.Os
.Sh NAME
.Nm mksnap_ffs
.Nd take a file system snapshot
.Sh SYNOPSIS
.Nm
.Ar snapshot_name
.Sh DESCRIPTION
The
.Nm
utility creates a snapshot named
.Ar snapshot_name .
This name is a path in the file system to be snapshotted.
Typically this is under the
.Pa .snap
directory in the root of the file system, but it can
be anywhere in the filesystem being snapshotted.
Snapshots can be listed using the
.Xr snapinfo 8
command.
.Pp
After a snapshot is taken it appears as a file.
The size of the snapshot file is equal to the size of the
file system from which it was taken.
It can be moved, renamed or deleted (which removes the snapshot).
.Pp
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
group.
.Sh EXAMPLES
Create a snapshot of
.Pa /usr/home
file system and mount the snapshot elsewhere:
.Bd -literal -offset indent
mksnap_ffs /usr/home/.snap/snap1
mdconfig -a -t vnode -o readonly -f /usr/home/.snap/snap1
mount -o ro /dev/md0 /mnt/
.Ed
.Pp
Delete a snapshot:
.Bd -literal -offset indent
rm /usr/home/.snap/snap1
.Ed
.Sh SEE ALSO
.Xr rm 1 ,
.Xr chmod 2 ,
.Xr chown 8 ,
.Xr mdconfig 8 ,
.Xr mount 8 ,
.Xr snapinfo 8
.Sh HISTORY
The
.Nm
utility first appeared in
.Fx 5.1 .
.Sh CAVEATS
The disk full situation is not handled gracefully and may
lead to a system panic when no free blocks are found.
.Pp
Every filesystem can have only up to 20 active snapshots.
When this limit is reached, attempting to create more snapshots
fails with
.Er ENOSPC ,
and
.Nm
reports that it is
.Dq out of space .