NetBSD/sbin/dump/dump.8

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.\"     from: @(#)dump.8	6.8 (Berkeley) 6/17/91
.\"	$Id: dump.8,v 1.5 1993/08/20 16:32:58 jtc Exp $
.\"
.Dd June 17, 1991
.Dt DUMP 8
.Os BSD 4
.Sh NAME
.Nm dump
.Nd filesystem backup
.Sh SYNOPSIS
.Nm dump
.Op Cm 0123456789fusdWn Op Ar argument ...
.Op Ar filesystem
.Sh DESCRIPTION
.Nm Dump
examines files
on a filesystem
and determines which files
need to be backed up. These files
are copied to the given disk, tape or other
storage medium for safe keeping (see
.Xr rdump 8
for
remote backups) .
A dump that is larger than the output medium is broken into
multiple volumes of a fixed size;
the actual size is determined by the tape size and density and/or
block count options below.
By default, the same output file name is used for each volume
after prompting the operator to change media.
.Pp
The following options are supported by
.Nm dump:
.Bl -tag -width 4n
.It Cm 0\-9
Dump levels.
A level 0, full backup,
guarantees the entire file system is copied.
A level number above 0,
incremental backup,
tells dump to
copy all files new or modified since the
last dump of the same or lower level. The default
level is 9.
.It Cm f Op Ar file
Write the backup to
.Ar file ;
.Ar file
may be a special device file
like
.Pa /dev/rmt12
(a tape drive),
.Pa /dev/rsd1c
(an optical drive),
an ordinary file,
or
.Ql Fl
(the standard output).
Multiple file names may be given as a single argument separated by commas.
Each file will be used for one dump volume in the order listed;
if the dump requires more volumes than the number of names given,
the last file name will used for all remaining volumes after prompting
for media changes.
.It Cm d Ar density
Set tape density to
.Ar density .
The default is 1600BPI.
.It Cm n
Whenever
.Nm dump
requires operator attention,
notify all operators in the group
.Dq operator
by means similar to a
.Xr wall 1 .
.It Cm s Ar feet
Attempt to caluculate the amount of tape needed
at a particular density.
If this amount is exceeded,
.Nm dump
prompts for a new tape.
It is recommended to be a bit conservative on this option.
The default tape length is 2300 feet.
.It Cm B Ar blocks
Set the size of the dump file to the specified number of 1024-byte blocks,
superceding the tape size and density.
.It Cm u
Update the file
.Pa /etc/dumpdates
after a successful dump.
The format of
.Pa /etc/dumpdates
is readable by people, consisting of one
free format record per line:
filesystem name,
increment level
and
.Xr ctime 3
format dump date.  
There may be only one entry per filesystem at each level.
The file
.Pa /etc/dumpdates
may be edited to change any of the fields,
if necessary.
.It Cm W
.Nm Dump
tells the operator what file systems need to be dumped.
This information is gleaned from the files
.Pa /etc/dumpdates
and
.Pa /etc/fstab .
The
.Cm W
option causes
.Nm dump
to print out, for each file system in
.Pa /etc/dumpdates
the most recent dump date and level,
and highlights those file systems that should be dumped.
If the 
.Cm W
option is set, all other options are ignored, and
.Nm dump
exits immediately.
.It Cm w
Is like W, but prints only those filesystems which need to be dumped.
.El
.Pp
.Nm Dump
requires operator intervention on these conditions:
end of tape,
end of dump,
tape write error,
tape open error or
disk read error (if there are more than a threshold of 32).
In addition to alerting all operators implied by the
.Cm n
key,
.Nm dump
interacts with the operator on 
.Em dump's
control terminal at times when
.Nm dump
can no longer proceed,
or if something is grossly wrong.
All questions
.Nm dump
poses
.Em must
be answered by typing \*(lqyes\*(rq or \*(lqno\*(rq,
appropriately.
.Pp
Since making a dump involves a lot of time and effort for full dumps,
.Nm dump
checkpoints itself at the start of each tape volume.
If writing that volume fails for some reason,
.Nm dump
will,
with operator permission,
restart itself from the checkpoint
after the old tape has been rewound and removed,
and a new tape has been mounted.
.Pp
.Nm Dump
tells the operator what is going on at periodic intervals,
including usually low estimates of the number of blocks to write,
the number of tapes it will take, the time to completion, and
the time to the tape change.
The output is verbose,
so that others know that the terminal
controlling
.Nm dump
is busy,
and will be for some time.
.Pp
In the event of a catastrophic disk event, the time required
to restore all the necessary backup tapes or files to disk
can be kept to a minimum by staggering the incremental dumps.
An efficient method of staggering incremental dumps
to minimize the number of tapes follows:
.Bl -bullet -offset indent
.It
Always start with a level 0 backup, for example:
.Bd -literal -offset indent
/sbin/dump 0ufds /dev/nrst1 54000 6000 /usr/src
.Ed
.Pp
This should be done at set intervals, say once a month or once every two months,
and on a set of fresh tapes that is saved forever.
.It
After a level 0, dumps of active file 
systems are taken on a daily basis,
using a modified Tower of Hanoi algorithm,
with this sequence of dump levels:
.Bd -literal -offset indent
3 2 5 4 7 6 9 8 9 9 ...
.Ed
.Pp
For the daily dumps, it should be possible to use a fixed number of tapes
for each day, used on a weekly basis.
Each week, a level 1 dump is taken, and
the daily Hanoi sequence repeats beginning with 3.
For weekly dumps, another fixed set of tapes per dumped file system is
used, also on a cyclical basis.
.El
.Pp
After several months or so, the daily and weekly tapes should get
rotated out of the dump cycle and fresh tapes brought in.
.Sh FILES
.Bl -tag -width /etc/dumpdates -compact
.It Pa /dev/rrp1g
default filesystem to dump from (system dependent).
.It Pa /dev/rmt8
default tape unit to dump to
.It Pa /etc/dumpdates
new format dump date record 
.It Pa /etc/fstab
dump table: file systems and frequency
.It Pa /etc/group
to find group
.Em operator
.El
.Sh SEE ALSO
.Xr rdump 8 ,
.Xr restore 8 ,
.Xr dump 5 ,
.Xr fstab 5
.Sh DIAGNOSTICS
Many, and verbose.
.Pp
Dump exits with zero status on success.
Startup errors are indicated with an exit code of 1;
abnormal termination is indicated with an exit code of 3.
.Sh BUGS
.Pp
Fewer than 32 read errors on the filesystem are ignored.
Each reel requires a new process, so parent processes for
reels already written just hang around until the entire tape
is written.
.Pp
.Nm Dump
with the
.Cm W
or
.Cm w
options does not report filesystems that have never been recorded
in
.Pa /etc/dumpdates ,
even if listed in
.Pa /etc/fstab .
.Pp
It would be nice if
.Nm dump
knew about the dump sequence,
kept track of the tapes scribbled on,
told the operator which tape to mount when,
and provided more assistance
for the operator running
.Xr restore .
.Sh HISTORY
A
.Nm
command appeared in Version 6 AT&T UNIX.