.Dd May 6, 2007
.Dt SNAP 8
.Os
.Sh NAME
.Nm snap
.Nd FreeBSD UFS2 Snapshot Management Tool
.Sh SYNOPSIS
.Nm
.Op Fl p
.Op Fl m
.Op Fl h
.Op Fl c Ar config_file
.Op Ar filesystem ...
.Sh DESCRIPTION
The
.Nm
utility
helps to either
.Pa periodically
or
.Pa manually
create snapshots.
.Pp
The options are as follows:
.Bl -tag -width indent
.It Fl p
Perform 
.Pa periodic 
task. It can only be used on the hour, 
otherwise nothing will happen.
If 
.Dq atHour
is given in the configuration file, then 
.Nm
will only run on the specified hour.
When this flag is not given, it is considered as a
.Pa manual
snapshot creation.
.It Fl m
List manually created snapshots and then exit.
.It Fl h
Show the help message.
.It Fl c Ar config_file
Specify the pathname of an alternative configuration file;
The default is 
.Pa /root/snap/snap.conf .
.El
.Pp
The 
.Nm
utility reads its configuration file when it starts up.
If 
.Pa filesystems 
are given and corresponding entries in the configuration file can be found, 
.Nm
will only handle these filesystems and ignore their
.Dq enable
flag in the configuration file.
.Pp
All snapshot files are created with the local creation time as their filename.
In periodic maintaining task,
three types of periodic snapshots, namely, hourly, daily, and weekly,
are created and rotated according to the settings in the configuration file. 
They are also hard-linked to 
.Dq nicknames ,
for example, the last hourly snapshot is hard-linked to
.Pa hour.0 .
.Sh EXAMPLES
The following command creates snapshots manually
according to the configuration file.
.Pp
.Dl snap
.Pp
To perform periodic maintaining, invoke
.Nm
in 
.Pa /etc/crontab 
as
.Pp
.Dl 0  *  *  *  *  root  /path/to/snap -p
.Pp
since periodic maintaining requires to be performed
on the hour.
.Pp
To manually create snapshots on filesystem / and /home and /var only:
.Pp
.Dl snap / /home /var
.Pp
This command will ignore the 
.Dq enable
flag in the configuration file.
If, say, /var is not found in the configuration file, nothing would happen.
.Pp
We can list manual created snapshots on filesystems / and /home:
.Pp
.Dl snap -m / /home
.Pp
or also specify an alternative path for the configuration file:
.Pp
.Dl snap -m -c /tmp/gg/snap.conf / /home
.Sh FILES
.Bl -tag -width /root/snap/snap.conf -compact
.It Pa /root/snap/snap.conf
configuration file
.It Pa hour.0
last hourly snapshot
.It Pa daily.0
last daily snapshot
.It Pa week.0
last weekly snapshot
.El
.Sh SEE ALSO
.Xr mount 8 ,
.Xr crontab 5 ,
.Xr mdconfig 8 ,
.Xr snapshot 8 
.Sh AUTHORS
This manual page was written by
.An Wu Chin-Hao wchunhao@cs.nctu.edu.tw .