DUMP(8) NetBSD System Manager's Manual DUMP(8)
NAME
dump, rdump - filesystem backup
SYNOPSIS
dump [-0123456789cenSu] [-B records] [-b blocksize] [-d density] [-f file] [-h level] [-k read blocksize] [-L label] [-r cachesize] [-s feet] [-T date] files-to-dump dump [-W | -w] (The 4.3BSD option syntax is implemented for backward compatibility, but is not documented here).
DESCRIPTION
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 stor- age medium for safe keeping (see the -f option below for doing remote backups). A dump that is larger than the output medium is broken into multiple volumes. On most media the size is determined by writing until an end-of-media indication is returned. On media that cannot reliably return an end-of-media indication (such as some cartridge tape drives) each volume is 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. files-to-dump is either a mountpoint of a filesystem, or a list of files and directories on a single filesystem to be backed up as a subset of the filesystem. In the former case, either the path to a mounted filesystem, or the device of an unmounted filesystem can be used. In the latter case, certain restrictions are placed on the backup: -u is ignored, the only dump level that is supported is -0, and all of the files must reside on the same filesystem. The following options are supported by dump: -0-9 Dump levels. A level 0, full backup, guarantees the entire file system is copied (but see also the -h option below). A level number above 0, incremental backup, tells dump to copy all files new or modified since the last dump of a lower level. The de- fault level is 9. -B records The number of kilobytes per volume, rounded down to a multiple of the blocksize. This option overrides the calculation of tape size based on length and density. -b blocksize The number of kilobytes per dump record. -c Modify the calculation of the default density and tape size to be more appropriate for cartridge tapes. -d density Set tape density to density. The default is 1600 Bits Per Inch (BPI). -e Eject tape automatically if a tape change is required. -f file Write the backup to file; file may be a special device file like /dev/rst0 (a tape drive), /dev/rsd1c (a disk drive), an ordinary file, or `-' (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 re- quires more volumes than the number of names given, the last file name will used for all remaining volumes after prompting for me- dia changes. If the name of the file is of the form "host:file", or "user@host:file", dump writes to the named file on the remote host using rmt(8). Note that methods more secure than rsh(1) (such as ssh(1)) can be used to invoke rmt(8) on the remote host, via the environment variable RCMD_CMD. See rcmd(3) for more de- tails. -h level Honor the user "nodump" flag only for dumps at or above the given level. The default honor level is 1, so that incremental backups omit such files but full backups retain them. -k read blocksize The size in kilobyte of the read buffers, rounded up to a multi- ple of the filesystem block size. Default is 32k. -L label The user-supplied text string label is placed into the dump head- er, where tools like restore(8) and file(1) can access it. Note that this label is limited to be at most LBLSIZE (currently 16) characters, which must include the terminating `\0'. -n Whenever dump requires operator attention, notify all operators in the group "operator" by means similar to a wall(1). -r cachesize Use that many buffers for read cache operations. A value of zero disables the read cache altogether, higher values improve read performance by reading larger data blocks from the disk and main- taining them in an LRU cache. See the -k option for the size of the buffers. Maximum is 512, the size of the cache is limited to 15% of the avail RAM by default. -s feet Attempt to calculate the amount of tape needed at a particular density. If this amount is exceeded, dump prompts for a new tape. It is recommended to be a bit conservative on this option. The default tape length is 2300 feet. -S Display an estimate of the backup size and the number of tapes required, and exit without actually performing the dump. -T date Use the specified date as the starting time for the dump instead of the time determined from looking in /etc/dumpdates. The for- mat of date is the same as that of ctime(3). This option is use- ful for automated dump scripts that wish to dump over a specific period of time. The -T option is mutually exclusive from the -u option. -u Update the file /etc/dumpdates after a successful dump. The for- mat of /etc/dumpdates is readable by people, consisting of one free format record per line: filesystem name, increment level and ctime(3) format dump date. There may be only one entry per filesystem at each level. The file /etc/dumpdates may be edited to change any of the fields, if necessary. If a list of files or subdirectories is being dumped (as opposed to and entire filesys- tem), then -u is ignored. -W dump tells the operator what file systems 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 file system in /etc/dumpdates the most recent dump date and lev- el, and highlights those file systems that should be dumped. If the -W option is set, all other options are ignored, and dump ex- its immediately. -w Is like W, but prints only those filesystems which need to be dumped. If dump honors the "nodump" flag, files with the "nodump" flag will not be backed up. If a directory has the "nodump" flag, this directory and any file or directory under it will not be backed up. 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 con- trol 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 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. 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 dump is busy, and will be for some time. 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: + Always start with a level 0 backup, for example: /sbin/dump -0u -f /dev/nrst1 /usr/src 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. + 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: 3 2 5 4 7 6 9 8 9 9 ... For the daily dumps, it should be possible to use a fixed num- ber 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. After several months or so, the daily and weekly tapes should get rotated out of the dump cycle and fresh tapes brought in. If dump receives a SIGINFO signal (see the "status" argument of stty(1)) whilst a backup is in progress, statistics on the amount completed, cur- rent transfer rate, and estimated finished time, will be written to the standard error output.
ENVIRONMENT
If the following environment variables exist, they are utilized by dump. TAPE If no -f option was specified, dump will use the device spec- ified via TAPE as the dump device. TAPE may be of the form "tapename", "host:tapename", or "user@host:tapename". RCMD_CMD dump will use RCMD_CMD rather than rsh(1) to invoke rmt(8) on the remote machine.
FILES
/dev/nrst0 default tape unit to use. Taken from _PATH_DEFTAPE in /usr/include/paths.h. /dev/rst* raw SCSI tape interface /etc/dumpdates dump date records /etc/fstab dump table: file systems and frequency /etc/group to find group operator
SEE ALSO
chflags(1), stty(1), fts(3), fstab(5), restore(8), rmt(8), st(4)
DIAGNOSTICS
Many, and verbose. 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.
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 nev- er been recorded in /etc/dumpdates, even if listed in /etc/fstab. When dumping a list of files or subdirectories, access privileges are re- quired to scan the directory (as this is done via the fts(3) routines rather than directly accessing the filesystem). 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 pro- vided more assistance for the operator running restore(8).
HISTORY
A dump command appeared in Version 6 AT&T UNIX. 4th Berkeley Distribution January 3, 1999 4
Powered by man-cgi (2024-08-26). Maintained for NetBSD by Kimmo Suominen. Based on man-cgi by Panagiotis Christias.