dump.8

<B>Digital的Unix操作系统VAX 4.2源码</B>

.\" SCCSID: @(#)dump.8	8.1	9/11/90
.TH dump 8
.SH Name
dump \- create file system dump
.SH Syntax
.B /etc/dump
[ \fIkey\fR [ \fIargument\fR... ] \fIfilesystem\fR ]
.SH Description
.NXR "dump command"
.NXR "file system" "incremental dumps"
The
.PN dump
command copies all files changed after a certain date
from a specified 
.I filesystem
to a file, a pipe, magnetic tapes, or disks. 
The
.I key
specifies the date and other options to be used by 
.PN dump .
.PP
Dumping a filesystem requires operator attention.  An operator
must intervene when the end of a tape or disk is reached,
when the end of the 
.PN dump 
occurs, or when an unrecoverable input disk
read error occurs (if more than 32 read errors occur).
In addition to alerting all operators in the operator group,
.PN dump
interacts with the operator at the control terminal when
.PN dump 
can no longer proceed, or if something is grossly wrong.
All questions that 
.PN dump
poses must be answered by typing yes or no.
.PP
Because a full dump uses considerable system time,
.PN dump
checkpoints itself at the start of each tape or disk
volume.  If writing that volume fails,
.PN dump
asks the operator to restart from the checkpoint after
the present tape or disk has been replaced.
.PP
The
.PN dump
utility reports to the operator periodically, giving
usually low estimates of the number of blocks to write,
the number of tapes or disks the dump will take, the
time to completion, and the time until the tape or
disk must be changed.  The output is verbose, so
that others know that the terminal controlling
.PN dump
is busy, and will be for some time.
.PP
This utility supports EOT handling which allows the use of
multiple media.  The utility prompts for the next volume when it
encounters the end of the current volume.
.SH Options 
.NXR "dump command" "keys"
With the
.PN dump
command, you specify a string of one or more of the
options described below.  If no options 
are specified, the
.I key
.B 9u
is assumed.
.TP 8 
.B  0\-9
Specifies the dump level.
All files 
that were modified 
since the last date stored
in the file
.PN /etc/dumpdates
for the same filesystem at lesser levels will be dumped.
If no date is determined by the level,
the beginning of time is assumed.  Thus, the level 
.B 0
causes the entire filesystem to be dumped.
.TP 8
.B B
Indicates that the next
.I argument
is a number that specifies the size, in 1024-byte blocks,
of a storage medium, such as a diskette or removable disk
cartridge.  See the first example.  
.TP 8
.B d
Indicates that the density of the tape, expressed in bits 
per inch, is taken from the next
.I argument.
This density is used in calculating the amount of tape
used per reel.  The default density is 1600 bpi.
.TP 8 
.B f
Places the dump on the file or device specified by the next
.I argument.
If the name of the file is \-,
.PN dump 
writes to standard output.
The default dump device is
.PN /dev/rmt0h .
.TP 8
.B n
Notifies, by means similar to a
.MS wall 1
command,
all users in the group operator when
.PN dump
needs operator attention.
.TP 8 
.B S 
Prints output file size in bytes, or number of volumes for devices.
See the third example.
.TP 8
.B s
Indicates that the next
.I argument
specifies the size of the dump tape, in feet.  When
the specified size is reached,
.PN dump
waits for the reel to be changed.  The default tape size
is 2300 feet.
.TP 8 
.B u
Writes the date of the beginning of the dump on the file
.PN /etc/dumpdates
if the 
.PN dump
completes successfully.  This file records a separate date for
each filesystem and each dump level.  The format of
.PN /etc/dumpdates
consists of one free format record per line:
filesystem name, increment level and
.MS ctime 3
format dump date.  The superuser can carefully edit
.PN /etc/dumpdates
to change any of the fields.
.TP 8 
.B W
Tells the operator which file systems need to be dumped.
This information is taken from the files
.PN /etc/dumpdates
and
.PN /etc/fstab .
The
.B W
option causes
.PN dump
to print out, for each file system in
.PN /etc/dumpdates ,
the most recent dump date and level,
and highlights those file systems that should be dumped.
If the 
.B W
option is used, all other options are ignored, and
.PN dump
exits immediately.
.TP 8 
.B w
Lists only those filesystems that need to be dumped.
.SH Examples
This example dumps the filesystem
.PN /dev/ra0a
to RX50 diskettes.  The 
.PN B
option is needed when running
.MS restore 8
to read this dump.
.EX
dump 9Bf 400 /dev/rra2a /dev/ra0a
.EE
This example dumps the filesystem
.PN /usr/users
to a 6250 bpi tape on a TU78 tape drive:
.EX
dump 0undf 6250 /dev/rmt?h /usr/users
.EE
This example reports number of bytes to be output
for a level 0 dump of the root
file system. 
Please note: the file test is not created.
.EX
dump 0Sf test /
.EE
.SH Restrictions
.NXR "dump command" "restrictions"
The 
.PN dump
programs returns a 1 on successful completion.
.PP
Sizes are based on 1600-bpi blocked tape.  
.PP
Anything fewer than 32 read errors on the filesystem
are ignored.
.PP
Each reel requires a new process, so parent processes
for reels already written remain until the entire
tape is written.
.SH Files
.TP 15
.PN /dev/rrp1g
Default filesystem to dump from
.TP
.PN /dev/rmt0h
Default tape unit to dump to
.TP
.PN /etc/dumpdates
Dump date record
.TP
.PN /etc/fstab
Dump table: file systems and frequency
.TP
.PN /etc/group
Operator group definition
.TP
.PN /dev/tty
Required for user interface
.SH See Also
dump(5), fstab(5), opser(8), restore(8), rrestore(8c)
.br
.I "Guide to Backup and Restore"