NAME

dump, rdump − incremental file system dump

SYNOPSIS

/etc/dump [ options [ arguments ] ] filesystem

DESCRIPTION

Dump backs up all files in filesystem, or files changed after a certain date, to magnetic tape.  Options is a string that specifies dump options, as shown below.  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 options are given, the default is 9u. 

OPTIONS

0−9 The "dump level."  All files in the filesystem that have been modified since the last dump at a lower dump level are copied to the tape.  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 since the "level 2" (Monday) backup.  A "level 0" dump copies the entire filesystem to tape. 

b factor
Blocking factor.  Specifies the blocking factor for tape writes. The default is 10 blocks per write.  Note that a tape block is 1024 bytes in size, or twice the size of a disk block.  The highest blocking factor available with some 6250bpi tape drives is 126.

c Cartridge.  Use a cartridge instead of the standard half-inch reel.  This sets the density to 1000bpi and the length to 1700 feet.  When dumping to a high-density (9-track) cartridge, include the s (size) option with the 3825 (feet) argument to properly fill each cartridge. 

d bpi Tape density.  The density of the tape, expressed in BPI, is taken from bpi.  This is used to keep a running tab on the amount of tape used per reel.  The default density is 1600.  Unless a higher density is specified explicitly, dump uses its default density—even if the tape drive is capable of higher-density operation (for instance, 6250bpi). 

f dump-file
Dump file.  Use dump-file as the file to dump to, instead of /dev/rmt8.  If dump-file is specified as ‘−’, dump to the standard output.  If the filename argument is of the form machine:device, dump to a remote machine.  Since dump is normally run by root, the name of the remote machine must appear in the .rhosts file of the local machine.  If dump is called as rdump, the tape defaults to dumphost:/dev/rmt8.  To direct the output to a desired remote machine, set up an alias for dumphost in the file /etc/hosts. 

n Notify.  When this option is specified, if dump requires attention, it sends a terminal message (similar to wall(1)) to all operators in the "operator" group.

s size Specify the size of the tape or cartridge in feet.  When the specified size is reached, dump waits for you to change the reel or cartridge.  The default size is 2300 feet, except when c (cartridge) is specified, in which case the default is 1700.  To estimate the size for a tape or cartridge of a nonstandard length, use the formula:

(length ∗ tracks) ∗ .9

u Update the dump record.  Add an entry to the file /etc/dumpdates, for each filesystem successfully dumped that includes the filesystem name, date, and dump level.  This file can be edited by the super-user. 

w List the filesystems that need backing up.  This information is gleaned from the files /etc/dumpdates and /etc/fstab.  When the w option is used, all other options are ignored.  After reporting, dump exits immediately. 

W Like w, but includes all filesystems that appear in /etc/dumpdates, along with information about their most recent dump dates and levels.  Filesystems that need backing up are highlighted. 

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 option, 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", as appropriate. 

Since backing up a disk can involve a lot of time and effort, dump checkpoints at the start of each tape volume.  If writing that volume fails for some reason, dump will, with operator permission, restart itself from the checkpoint after a defective tape has been rewound and replaced. 

dump reports periodically, and in  verbose fashion.  Each report includes estimates of the percentage of the dump completed and how long it will take to complete the dump. 

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(8). While preparing for a full dump, it is a good idea to clean the drive and heads.

Incremental dumps allow for convenient backup and recovery on a more frequent basis of active files, with a minimum of tape and time.  However there are some tradeoffs.  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 dump tapes.  Another consideration is the desire to keep unnecessary duplication of files to a minimum to save both operator time and tape 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 tradeoff between these goals. 

    Sun MonTueWedThuFri
Week 1:Full55553
Week 2:    55553
Week 3:    55553
Week 4:    55553

Although the Tuesday—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. 

FILES

/dev/rmt8 default tape unit to dump to

/etc/dumpdates new format dump date record

/etc/fstab dump table: file systems and frequency

/etc/group to find group operator

SEE ALSO

restore(8), dump(5), fstab(5)

DIAGNOSTICS

While running, dump emits many verbose messages. 

Exit Codes

0normal exit when w or W options are used. 

1normal exit. 

2error − restart writing from last checkpoint. 

3abort − no checkpoint attempted. 

BUGS

Sizes are based on 1600 BPI blocked tape; the raw tape device has to be used to approach these densities. 

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. 

Sun Release 3.2  —  Last change: 22 July 1986