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Linux命令：dump

功能说明：备份文件系统。

语　　法：dump [-cnu][-0123456789][-b <区块大小>][-B <区块数目>][-d <密度>][-f <设备名称>][-h <层级>][-s <磁带长度>][-T <日期>][目录或文件系统] 或 dump [-wW]

补充说明：dump为备份工具程序，可将目录或整个文件系统备份至指定的设备，或备份成一个大文件。 参　　数： 　-0123456789 　备份的层级。 　-b<区块大小> 　指定区块的大小，单位为KB。 　-B<区块数目> 　指定备份卷册的区块数目。 　-c 　修改备份磁带预设的密度与容量。 　-d<密度> 　设置磁带的密度。单位为BPI。 　-f<设备名称> 　指定备份设备。 　-h<层级> 　当备份层级等于或大雨指定的层级时，将不备份用户标示为"nodump"的文件。 　-n 　当备份工作需要管理员介入时，向所有"operator"群组中的使用者发出通知。 　-s<磁带长度> 　备份磁带的长度，单位为英尺。 　-T<日期> 　指定开始备份的时间与日期。 　-u 　备份完毕后，在/etc/dumpdates中记录备份的文件系统，层级，日期与时间等。 　-w 　与-W类似，但仅显示需要备份的文件。 　-W 　显示需要备份的文件及其最后一次备份的层级，时间与日期。

英文版本，欢迎翻译：

NAME dump - ext2 filesystem backup

SYNOPSIS dump [-0123456789ackMnSu] [-B records] [-b blocksize] [-d density] [-e inode number] [-f file] [-F script] [-h level] [-L label] [-s feet] [-T date] file-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 an ext2 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 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 specifying cartridge media, or via the tape size, 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.

file-to-dump is either a mountpoint of a filesystem or a directory to be backed up as a subset of a 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 not allowed and the only dump level that is supported is -0.

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 1 KB blocks per volume. This option overrides the end-of-media detection, and calculation of tape size based on length and density.

-a ``auto-size'. Bypass all tape length calculations, and write un? til an end-of-media indication is returned. This works best for most modern tape drives, and is the default. Use of this option is particularly recommended when appending to an existing tape, or using a tape drive with hardware compression (where you can never be sure about the compression ratio).

-b blocksize The number of kilobytes per dump record. Since the IO system slices all requests into chunks of MAXBSIZE (typically 64KB), it is not possible to use a larger blocksize without having problems later with restore(8). Therefore dump will constrain writes to MAXBSIZE. The default blocksize is 10.

-c Change the defaults for use with a cartridge tape drive, with a density of 8000 bpi, and a length of 1700 feet. Specifying a car? tridge drive overrides the end-of-media detection.

-e inode Exclude inode from the dump (you can use stat to find the inode number for a file or directory).

-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.

-d density Set tape density to density. The default is 1600BPI. Specifying a tape density overrides the end-of-media detection.

-f file Write the backup to file; file may be a special device file like /dev/st0 (a tape drive), /dev/rsd1c (a floppy disk drive), an or? dinary 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 requires more volumes than the number of names given, the last file name will used for all remaining volumes after prompting for media 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). The default path name of the remote rmt(8) program is /etc/rmt; this can be overridden by the environment variable RMT.

-F script Run script at the end of each tape. The device name and the cur? rent volume number are passed on the command line. The script must return 0 if dump should continue without asking the user to change the tape, 1 if dump dump should continue but ask the user to change the tape. Any other exit code will cause dump to abort. For security reasons, dump reverts back to the real user ID and the real group ID before running the script.

-k Use Kerberos authentication to talk to remote tape servers. (On? ly available if this option was enabled when dump was compiled.)

-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 `.

-M Enable the multi-volume feature. The name specified with -f is treated as a prefix and dump writes in sequence to 001, 002 etc. This can be useful when dumping to files on an ext2 partition, in order to bypass the 2GB file size limitation.

-n Whenever dump requires operator attention, notify all operators in the group ``operator' by means similar to a wall(1).

-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. Specifying the tape size overrides end-of-media detection.

-S Size estimate. Determine the amount of space that is needed to perform the dump without actually doing it, and display the esti? mated number of bytes it will take. This is useful with incremen? tal dumps to determine how many volumes of media will be needed.

-T date Use the specified date as the starting time for the dump instead of the time determined from looking in /etc/dumpdates. The format of date is the same as that of ctime(3). This option is useful for automated dump scripts that wish to dump over a specific pe? riod 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.

-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 all file systems in /etc/dumpdates, and regognized file systems in /etc/fstab. the most recent dump date and level, and highlights those that should be dumped. If the -W option is set, all other options are ignored, and dump exits immediately.

-w Is like -W, but prints only recognized filesystems in /etc/fstab which need to be dumped.