dump(1M) dump(1M)
NAME
dump, rdump - incremental filesystem backup for EFS filesystems
SYNOPSIS
dump [ key [ argument ... ] ] filesystem
rdump [ key [ argument ... ] ] filesystem
DESCRIPTION
dump and rdump are applicable only to EFS filesystems, use xfsdump(1m)
for XFS filesystems.
dump backs up all files in filesystem or files changed after a certain
date to magnetic tape or files. The key specifies the date and other
options about the dump. key consists of characters from the set
0123456789fusCcdbWwn. Any arguments supplied for specific options are
given as subsequent words on the command line, in the same order as that
of the options listed.
If no key is given, the key is assumed to be 9u and the filesystem
specified is dumped to the default tape device /dev/tape.
0-9 This number is the dump level. All files modified since the last
date stored in the file /etc/dumpdates for the same filesystem at
lesser levels are dumped. If no date is determined by the level,
the beginning of time is assumed; thus the option 0 causes the
entire filesystem to be dumped. For instance, if you did a level 2
dump on Monday, followed by a level 4 dump on Tuesday, a subsequent
level 3 dump on Wednesday would contain all files modified or added
to the filesystem since the level 2 (Monday) backup. A level 0 dump
copies the entire filesystem to the dump volume.
f Place the dump on the next argument file instead of the default tape
device /dev/tape. If the name of the file is ``-'', dump writes to
standard output. If the name of the file is of the format
machine:device, the filesystem is dumped across the network to the
remote machine. Since dump is normally run by root, the name of the
local machine must appear in the .rhosts file of the remote machine.
If the filename argument is of the form user@machine:device, dump
attempts to execute as the specified user on the remote machine.
The specified user must have a .rhosts file on the remote machine
that allows root from the local machine. dump creates a remote
server, /etc/rmt, on the client machine to access the tape device.
u If the dump completes successfully, write the date of the beginning
of the dump on file /etc/dumpdates. This file records a separate
date for each filesystem and each dump level. The format of
/etc/dumpdates is readable by people, consisting of one free format
record per line: filesystem name, increment level, and ctime(3C)
format dump date. /etc/dumpdates can be edited to change any of the
fields, if necessary.
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s The size of the dump tape is specified in feet. The number of feet
is taken from the next argument. It is recommended that the C option
be used instead, as it is more predictable. When the specified size
is reached, dump prompts the operator and wait for the reel/volume
to be changed.
d The density of the tape, expressed in BPI (bytes per inch), is taken
from the next argument. This is used in calculating the amount of
tape used per reel. It is recommended that the C option be used
instead, as it is more predictable.
b The blocking factor (number of 1-kilobyte blocks written out
together) is taken from the next argument. The default is 10. The
default blocking factor for tapes of density 6250 BPI and greater is
32. For some network, tape type, and server combinations, there may
be a significant throughput improvement by using a blocking factor
of 32, rather than the default of 10, when using rdump. If values
larger than 32 are used, restore does not correctly determine the
block size unless the b option is also used. To maximize tape
utilization, use a blocking factor that is a multiple of 8. For
most types of supported tape drives, the greatest capacity and tape
throughput is obtained using a blocking factor of 128 or even
larger; note that restore(1M) automatically determines the blocking
factor only if it is 32 or less.
C This specifies the total tape capacity in 1-kilobyte blocks,
overriding the c, s, and d arguments if they are also given. Unlike
the size and density arguments, the capacity is used as specified,
no correction factors are applied. Since capacity lost to retries
or underruns (by the drive), are not taken into account, you should
be conservative when specifying capacity. The argument is parsed
with strtoul(3C), so it can be in any base (for example, a 0x prefix
specifies a hexadecimal value, a 0 prefix specifies octal, no prefix
is decimal). The argument can have a k, K, m, or M suffix. The
first two multiply the value by 1024, the third and fourth multiply
by 1048576, so a tape with a 2.2 Gbyte capacity might be specified
as C 2m allowing 10% loss to retries, and so on.
When the specified capacity has been written, dump prompts the
operator and wait for the reel/volume to be changed. It is not
currently possible to specify different capacitties for different
volumes of multi-volume backups.
c Indicates that the tape is a cartridge tape instead of the standard
default half-inch reel. This should always be specified when using
cartridge tapes, unless the C option is used. The values for
blocking factor, size, and density are taken to be 10 (1-kilobyte
blocks), 5400 feet, and 1000 BPI respectively unless overridden with
the b, s, or d option.
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dump(1M) dump(1M)
W dump tells the operator what filesystems need to be dumped. This
information is gleaned from the files /etc/dumpdates and /etc/fstab.
The W option causes dump to print out, for each filesystem in
/etc/dumpdates, the most recent dump date and level and highlights
those filesystems that should be dumped. The mnt_freq field in the
/etc/fstab entry of the filesystem must be nonzero for dump to
determine whether the filesystem should be dumped or not. If the W
option is set, no other option must be given and dump exits
immediately.
w Is like W, but prints only those filesystems that need to be dumped.
n Whenever dump requires operator attention, notify by means similar
to a wall(1) all of the operators in the group operator.
dump reads the character device associated with the filesystem and dumps
the contents onto the specified tape device. It searches /etc/fstab to
find the associated character device.
NOTES
rdump is a link to dump.
Operator Intervention
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 n key, dump interacts with the operator on
dump's control terminal at times when dump can no longer proceed or if
something is grossly wrong. All questions dump poses must be answered by
typing yes or no, appropriately.
Since making a dump involves a lot of time and effort for full dumps,
dump checkpoints itself at the start of each tape volume. If writing
that volume fails for some reason, dump, with operator permission,
restarts itself from the checkpoint after the old tape has been rewound
and removed and a new tape has been mounted.
dump reports periodically, including usually the percentage of the dump
completed, low estimates of the number of blocks to write in 1-kilobyte
blocks (or, more strictly, TP_BSIZE units from protocols/dumprestore.h),
the number of tapes it will take, the time to completion, and the time to
the tape change. The estimated time is given as hours:minutes and is
based on the time taken to dump the blocks already on tape. It is normal
for this estimate to show variance, and the estimate improves over time.
The output is verbose, so that others know that the terminal controlling
dump is busy and will be for some time.
Suggested Dump Schedule
It is vital to perform full level 0 dumps at regular intervals. When
performing a full dump, bring the machine down to single-user mode using
shutdown -is. Otherwise the dump may not be internally consistent and
may not restore correctly. While preparing for a full dump, it is a good
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dump(1M) dump(1M)
idea to clean the tape drive and heads (most types of drives require head
cleaning for approximately every 30 hours of tape motion).
Incremental dumps allow for convenient backup and recovery of active
files on a more frequent basis, with a minimum of media and time.
However, there are some trade-offs. First, the interval between backups
should be kept to a minimum (once a day at least). To guard against data
loss as a result of a media failure (a rare but possible occurrence), it
is a good idea to capture active files on (at least) two sets of dump
volumes. Keep unnecessary duplication of files to a minimum to save both
operator time and media storage. A third consideration is the ease with
which a particular backed up version of a file can be located and
restored. The following four-week schedule offers a reasonable trade-off
between these goals.
Sun Mon Tue Wed Thu Fri
Week 1: Full 5 5 5 5 3
Week 2: 5 5 5 5 3
Week 3: 5 5 5 5 3
Week 4: 5 5 5 5 3
Although the Tuesday through Friday incrementals contain extra copies of
files from Monday, this scheme assures that any file modified during the
week can be recovered from the previous day's incremental dump.
Dump Parameters
Since it is suggested that the C option be used instead of the density
and size options, and since those values are almost never really correct
for any tape drive except 9 track tapes, recommended values for these
parameters are no longer suggested in this man page. As an example of
the capacity, a typical QIC150 cartridge would use C 140k, a DDS1 90
meter DAT or 112 meter 8mm (8200 mode) cartridge would use C 1800k, and a
DDS2 120 meter cartridge would use C 3800k.
EXAMPLES
/dev/usr /usr efs rw,raw=/dev/rdsk/dks0d1s6 0 0
Here are a few examples on how to dump the /usr filesystem with the above
/etc/fstab entry.
dump 0Cfu 140k guest@kestrel:/dev/tape /usr
does a level 0 dump of /usr onto a remote cartridge tape device /dev/tape
on host kestrel using the guest account. dump also updates the file
/etc/dumpdates.
dump 2Cu 140k /usr
does a level 2 dump of /usr to the local cartridge tape device /dev/tape
and also updates the file /etc/dumpdates.
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dump(1M) dump(1M)
dump 0Cb 140k 128 /usr
does a level '0' dump of /usr to the local tape device /dev/tape using a
blocking factor of 128. The tape is specified to have a capacity of 140
megabytes in the second, which allows for retries, space lost to
repositioning, and so on. It is also appropriate for a QIC 150 quarter-
inch tape drive. The ordering of the arguments depends on the ordering
of the key.
dump 1Cf 140k /dev/mt/tps0d7 /usr
dump 1Cf 140k /dev/mt/tps0d7 /dev/rdsk/dks0d1s6
both do a level 1 dump of /usr to the local cartridge tape.
dump /usr
does a level 9 dump of /usr to the local tape device /dev/tape and
updates the file /etc/dumpdates.
dump 9uCf 2048k /dev/mt/tps0d6nrnsv /os
dump 9uCf 2m /dev/mt/tps0d6nrnsv /os
Both do a level 9 dump of /os to the local tape device
/dev/mt/tps0d6nrnsv where the tape device being used is an 8mm tape
drive, and we are being somewhat optimistic about the capacity.
dump W
prints out, for each filesystem in /etc/dumpdates, the most recent dump
date and level and highlights those filesystems that should be dumped.
FILES
/dev/tape default tape unit to dump to
/etc/dumpdates new format dump date record
/etc/fstab dump table: filesystems and frequency
/etc/group to find group operator
SEE ALSO
restore(1M), rmt(1M), shutdown(1M), xfsdump(1M), xfsrestore(1M), wall(1),
ctime(3C), fstab(4), group(4), rhosts(4), dump(5), mtio(7).
DIAGNOSTICS
While running, dump emits many verbose messages.
The exit codes are
0 Normal exit
1 Startup errors encountered
3 Abnormal termination
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dump(1M) dump(1M)
BUGS
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.
dump with the W or w options does not report filesystems that have never
been recorded in /etc/dumpdates, even if listed in /etc/fstab.
It would be nice if 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 restore.
It is recommended that incremental dumps also be performed with the
system running in single-user mode.
dump needs accurate information regarding the length and density of the
tapes used. It can dump the filesystem on multiple volumes, but since
there is no way of specifying different sizes for multiple tapes, all
tapes used should be at least as long as the specified/default length.
If dump reaches the end of the tape volume unexpectedly (as a result of a
longer than actual length specification), it aborts the entire dump.
This can be a problem when writing multiple dumps to the same physical
tape, or when the tape drive supports hardware compression, and it is not
possible to determine the average compression ratio ahead of time.
Currently the only solution to this problem in this version of dump is to
be conservative in specifying capacity.
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