Linux下文件数据的备份和恢复命令： dump 和 restore
1. dump的Linux Manual：// 用于数据的转储，备份。
转储dump可能用到的几个文件：
/dev/st0
default tape unit to dump to
/etc/dumpdates
dump date records
/etc/fstab
dump table: file systems and frequency
/etc/mtab
dump table: mounted file systems
/etc/group
to find group operator
DUMP(8) System management commands DUMP(8)
NAME
dump - ext2/3 filesystem backup
SYNOPSIS
dump [-level#] [-ackMnqSuv] [-A file] [-B records] [-b blocksize] [-d
density] [-D file] [-e inode numbers] [-E file] [-f file] [-F script]
[-h level] [-I nr errors] [-jcompression level] [-L label] [-Q file]
[-s feet] [-T date] [-y] [-zcompression level] files-to-dump
dump [-W | -w]
DESCRIPTION
Dump examines files on an ext2/3 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 oper-
ator to change media.
files-to-dump is either a mountpoint of a filesystem or a list of files
and directories 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, the only dump
level that is supported is 0 and all the files and directories must
reside on the same filesystem.
OPTIONS
The following options are supported by dump:
-level#
The dump level (any integer). 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 default level is 0. Historically only levels 0 to 9
were usable in dump, this version is able to understand any
integer as a dump level.
-a “auto-size”. Bypass all tape length calculations, and write
until 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).
-A archive_file
Archive a dump table-of-contents in the specified archive_file
to be used by restore(8) to determine whether a file is in the
dump file that is being restored.
-b blocksize
The number of kilobytes per dump record. The default blocksize
is 10, unless the -d option has been used to specify a tape den-
sity of 6250BPI or more, in which case the default blocksize is
32. Th maximal value is 1024. Note however that, since the IO
system slices all requests into chunks of MAXBSIZE (which can be
as low as 64kB), you can experience problems with dump(8) and
restore(8) when using a higher value, depending on your kernel
and/or libC versions.
-B records
The number of 1 kB blocks per volume. Not normally required, as
dump can detect end-of-media. When the specified size is
reached, dump waits for you to change the volume. This option
overrides the calculation of tape size based on length and den-
sity. If compression is on this limits the size of the com-
pressed output per volume. Multiple values may be given as a
single argument separated by commas. Each value will be used
for one dump volume in the order listed; if dump creates more
volumes than the number of values given, the last value will be
used for the remaining volumes. This is useful for filling up
already partially filled media (and then continuing with full
size volumes on empty media) or mixing media of different sizes.
-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
cartridge drive overrides the end-of-media detection.
-d density
Set tape density to density. The default is 1600BPI. Specifying
a tape density overrides the end-of-media detection.
-D file
Set the path name of the file storing the information about the
previous full and incremental dumps. The default location is
/etc/dumpdates.
-e inodes
Exclude inodes from the dump. The inodes parameter is a comma
separated list of inode numbers (you can use stat(1) to find the
inode number for a file or directory).
-E file
Read list of inodes to be excluded from the dump from the text
file file. The file file should be an ordinary file containing
inode numbers separated by newlines.
-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
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 requires more volumes than the number of names given, the
last file name will used for all remaining volumes after prompt-
ing 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 (which should already exist, dump doesn’t create a
new remote file) 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 (except for the last one).
The device name and the current 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 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.
-h level
Honor the user nodump flag UF_NODUMP only for dumps at or above
the given level. The default honor level is 1, so that incre-
mental backups omit such files but full backups retain them.
-I nr errors
By default, dump will ignore the first 32 read errors on the
file system before asking for operator intervention. You can
change this using this flag to any value. This is useful when
running dump on an active filesystem where read errors simply
indicate an inconsistency between the mapping and dumping
passes.
A value of 0 means that all read errors will be ignored.
-jcompression level
Compress every block to be written on the tape using bzlib
library. This option will work only when dumping to a file or
pipe or, when dumping to a tape drive, if the tape drive is
capable of writing variable length blocks. You will need at
least the 0.4b24 version of restore in order to extract com-
pressed tapes. Tapes written using compression will not be com-
patible with the BSD tape format. The (optional) parameter spec-
ifies the compression level bzlib will use. The default compres-
sion level is 2. If the optional parameter is specified, there
should be no white space between the option letter and the
parameter.
-k Use Kerberos authentication to talk to remote tape servers.
(Only available if this option was enabled when dump was com-
piled.)
-L label
The user-supplied text string label is placed into the dump
header, where tools like restore(8) and file(8) can access it.
Note that this label is limited to be at most LBLSIZE (currently
16) characters, which must include the terminating \0.
-m If this flag is specified, dump will optimise the output for
inodes having been changed but not modified since the last dump
(’changed’ and ’modified’ have the meaning defined in stat(2) ).
For those inodes, dump will save only the metadata, instead of
saving the entire inode contents. Inodes which are either
directories or have been modified since the last dump are saved
in a regular way. Uses of this flag must be consistent, meaning
that either every dump in an incremental dump set have the flag,
or no one has it.
If you use this option, be aware that many programs that unpack
files from archives (e.g. tar, rpm, unzip, dpkg) may set files’
mtimes to dates in the past. Files installed in this way may
not be dumped correctly using "dump -m" if the modified mtime is
earlier than the previous level dump.
Tapes written using such ’metadata only’ inodes will not be com-
patible with the BSD tape format or older versions of restore.
-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).
-q Make dump abort immediately whenever operator attention is
required, without prompting in case of write errors, tape
changes etc.
-Q file
Enable the Quick File Access support. Tape positions for each
inode are stored into the file file which is used by restore (if
called with parameter -Q and the filename) to directly position
the tape at the file restore is currently working on. This saves
hours when restoring single files from large backups, saves the
tapes and the drive’s head.
It is recommended to set up the st driver to return logical tape
positions rather than physical before calling dump/restore with
parameter -Q. Since not all tape devices support physical tape
positions those tape devices return an error during dump/restore
when the st driver is set to the default physical setting.
Please see the st(4) man page, option MTSETDRVBUFFER , or the
mt(1) man page, on how to set the driver to return logical tape
positions.
Before calling restore with parameter -Q, always make sure the
st driver is set to return the same type of tape position used
during the call to dump. Otherwise restore may be confused.
This option can be used when dumping to local tapes (see above)
or to local files.
-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
estimated number of bytes it will take. This is useful with
incremental 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) followed by an
rfc822 timezone specification: either a plus or minus sign fol-
lowed by two digits for the number of hours and two digits for
the minutes. For example, -0800 for eight hours west of Green-
wich or +0230 for two hours and a half east of Greenwich. This
timezone offset takes into account daylight savings time (if
applicable to the timezone): UTC offsets when daylight savings
time is in effect will be different than offsets when daylight
savings time is not in effect. For backward compatibility, if no
timezone is specified, a local time is assumed. This option is
useful for automated dump scripts that wish to dump over a spe-
cific 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 followed by a rfc822 timezone
specification (see the -u option for details). If no timezone
offset is specified, times are interpreted as local. Whenever
the file is written, all dates in the file are converted to the
local time zone, without changing the UTC times. There may be
only one entry per filesystem at each level. The file /etc/dump-
dates may be edited to change any of the fields, if necessary.
-v The -v (verbose) makes dump to print extra information which
could be helpful in debug sessions.
-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 recognized file systems in
/etc/mtab and /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/mtab
and /etc/fstab which need to be dumped.
-y Compress every block to be written to the tape using the lzo
library. This doesn’t compress as well as the zlib library but
it’s much faster. This option will work only when dumping to a
file or pipe or, when dumping to a tape drive, if the tape drive
is capable of writing variable length blocks. You will need at
least the 0.4b34 version of restore in order to extract com-
pressed tapes. Tapes written using compression will not be com-
patible with the BSD tape format.
-zcompression level
Compress every block to be written on the tape using zlib
library. This option will work only when dumping to a file or
pipe or, when dumping to a tape drive, if the tape drive is
capable of writing variable length blocks. You will need at
least the 0.4b22 version of restore in order to extract com-
pressed tapes. Tapes written using compression will not be com-
patible with the BSD tape format. The (optional) parameter spec-
ifies the compression level zlib will use. The default compres-
sion level is 2. If the optional parameter is specified, there
should be no white space between the option letter and the
parameter.
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 is more than a threshold of nr errors). 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 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, includ-
ing 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 mini-
mum by staggering the incremental dumps. An efficient method of stag-
gering incremental dumps to minimize the number of tapes follows:
— Always start with a level 0 backup, for example:
/sbin/dump -0u -f /dev/st0 /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 for-
ever.
— 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 number
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.
(The 4.3BSD option syntax is implemented for backward compatibility but
is not documented here.)
ENVIRONMENT
TAPE If no -f option was specified, dump will use the device speci-
fied via TAPE as the dump device. TAPE may be of the form tape-
name, host:tapename, or user@host:tapename.
RMT The environment variable RMT will be used to determine the path-
name of the remote rmt(8) program.
RSH Dump uses the contents of this variable to determine the name of
the remote shell command to use when doing remote backups (rsh,
ssh etc.). If this variable is not set, rcmd(3) will be used,
but only root will be able to do remote backups.
FILES
/dev/st0
default tape unit to dump to
/etc/dumpdates
dump date records
/etc/fstab
dump table: file systems and frequency
/etc/mtab
dump table: mounted file systems
/etc/group
to find group operator
SEE ALSO
fstab(5), restore(8), rmt(8)
DIAGNOSTICS
Many, and verbose.
COMPATIBILITY
The format of the /etc/dumpdates file has changed in release 0.4b34,
however, the file will be read correctly with either pre-0.4b34 or
0.4b34 and later versions of dump provided that the machine on which
dump is run did not change timezones (which should be a fairly rare
occurrence).
EXIT STATUS
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
It might be considered a bug that this version of dump can only handle
ext2/3 filesystems. Specifically, it does not work with FAT filesys-
tems.
Fewer than 32 read errors (change this with -I) on the filesystem are
ignored. If noticing read errors is important, the output from dump can
be parsed to look for lines that contain the text ’read error’.
When a read error occurs, dump prints out the corresponding physical
disk block and sector number and the ext2/3 logical block number. It
doesn’t print out the corresponding file name or even the inode number.
The user has to use debugfs(8), commands ncheck and icheck to translate
the ext2blk number printed out by dump into an inode number, then into
a file name.
Each reel requires a new process, so parent processes for reels already
written just hang around until the entire tape is written.
The estimated number of tapes is not correct if compression is on.
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.
Dump cannot do remote backups without being run as root, due to its
security history. Presently, it works if you set it setuid (like it
used to be), but this might constitute a security risk. Note that you
can set RSH to use a remote shell program instead.
AUTHOR
The dump/restore backup suite was ported to Linux’s Second Extended
File System by Remy Card . He maintained the initial
versions of dump (up and including 0.4b4, released in January 1997).
Starting with 0.4b5, the new maintainer is Stelian Pop
.
AVAILABILITY
The dump/restore backup suite is available from
HISTORY
A dump command appeared in Version 6 AT&T UNIX.
BSD version 0.4b41 of January 2, 2006 DUMP(8)
RESTORE(8) System management commands RESTORE(8)
NAME
restore - restore files or file systems from backups made with dump
SYNOPSIS
restore -C [-cdHklMvVy] [-b blocksize] [-D filesystem] [-f file] [-F
script] [-L limit] [-s fileno] [-T directory]
restore -i [-acdhHklmMNouvVy] [-A file] [-b blocksize] [-f file] [-F
script] [-Q file] [-s fileno] [-T directory]
restore -P file [-acdhHklmMNuvVy] [-b blocksize] [-f file] [-F script]
[-s fileno] [-T directory] [-X filelist] [ file ... ]
restore -R [-cdHklMNuvVy] [-b blocksize] [-f file] [-F script] [-s
fileno] [-T directory]
restore -r [-cdHklMNuvVy] [-b blocksize] [-f file] [-F script] [-s
fileno] [-T directory]
restore -t [-cdhHklMNuvVy] [-A file] [-b blocksize] [-f file] [-F
script] [-Q file] [-s fileno] [-T directory] [-X filelist] [ file ... ]
restore -x [-adchHklmMNouvVy] [-A file] [-b blocksize] [-f file] [-F
script] [-Q file] [-s fileno] [-T directory] [-X filelist] [ file ... ]
DESCRIPTION
The restore command performs the inverse function of dump(8). A full
backup of a file system may be restored and subsequent incremental
backups layered on top of it. Single files and directory subtrees may
be restored from full or partial backups. Restore works across a net-
work; to do this see the -f flag described below. Other arguments to
the command are file or directory names specifying the files that are
to be restored. Unless the -h flag is specified (see below), the
appearance of a directory name refers to the files and (recursively)
subdirectories of that directory.
Exactly one of the following flags is required:
-C This mode allows comparison of files from a dump. Restore reads
the backup and compares its contents with files present on the
disk. It first changes its working directory to the root of the
filesystem that was dumped and compares the tape with the files
in its new current directory. See also the -L flag described
below.
-i This mode allows interactive restoration of files from a dump.
After reading in the directory information from the dump,
restore provides a shell like interface that allows the user to
move around the directory tree selecting files to be extracted.
The available commands are given below; for those commands that
require an argument, the default is the current directory.
add [arg]
The current directory or specified argument is added to
the list of files to be extracted. If a directory is
specified, then it and all its descendents are added to
the extraction list (unless the -h flag is specified on
the command line). Files that are on the extraction list
are prepended with a “*” when they are listed by ls.
cd arg Change the current working directory to the specified
argument.
delete [arg]
The current directory or specified argument is deleted
from the list of files to be extracted. If a directory is
specified, then it and all its descendents are deleted
from the extraction list (unless the -h flag is specified
on the command line). The most expedient way to extract
most of the files from a directory is to add the direc-
tory to the extraction list and then delete those files
that are not needed.
extract
All files on the extraction list are extracted from the
dump. Restore will ask which volume the user wishes to
mount. The fastest way to extract a f ew files is to
start with the last volume and work towards the first
volume.
help List a summary of the available commands.
ls [arg]
List the current or specified directory. Entries that are
directories are appended with a “/”. Entries that have
been marked for extraction are prepended with a “*”. If
the verbose flag is set, the inode number of each entry
is also listed.
pwd Print the full pathname of the current working directory.
quit Restore immediately exits, even if the extraction list is
not empty.
setmodes
All directories that have been added to the extraction
list have their owner, modes, and times set; nothing is
extracted from the dump. This is useful for cleaning up
after a restore has been prematurely aborted.
verbose
The sense of the -v flag is toggled. When set, the ver-
bose flag causes the ls command to list the inode numbers
of all entries. It also causes restore to print out
information about each file as it is extracted.
-P file
Restore creates a new Quick File Access file file from an exist-
ing dump file without restoring its contents.
-R Restore requests a particular tape of a multi-volume set on
which to restart a full restore (see the -r flag below). This is
useful if the restore has been interrupted.
-r Restore (rebuild) a file system. The target file system should
be made pristine with mke2fs(8), mounted, and the user cd’d into
the pristine file system before starting the restoration of the
initial level 0 backup. If the level 0 restores successfully,
the -r flag may be used to restore any necessary incremental
backups on top of the level 0. The -r flag precludes an interac-
tive file extraction and can be detrimental to one’s health (not
to mention the disk) if not used carefully. An example:
mke2fs /dev/sda1
mount /dev/sda1 /mnt
cd /mnt
restore rf /dev/st0
Note that restore leaves a file restoresymtable in the root
directory to pass information between incremental restore
passes. This file should be removed when the last incremental
has been restored.
Restore, in conjunction with mke2fs(8) and dump(8), may be used
to modify file system parameters such as size or block size.
-t The names of the specified files are listed if they occur on the
backup. If no file argument is given, the root directory is
listed, which results in the entire content of the backup being
listed, unless the -h flag has been specified. Note that the -t
flag replaces the function of the old dumpdir(8) program. See
also the -X option below.
-x The named files are read from the given media. If a named file
matches a directory whose contents are on the backup and the -h
flag is not specified, the directory is recursively extracted.
The owner, modification time, and mode are restored (if possi-
ble). If no file argument is given, the root directory is
extracted, which results in the entire content of the backup
being extracted, unless the -h flag has been specified. See
also the -X option below.
OPTIONS
The following additional options may be specified:
-a In -i or -x mode, restore does ask the user for the volume num-
ber on which the files to be extracted are supposed to be (in
order to minimise the time by reading only the interesting vol-
umes). The -a option disables this behaviour and reads all the
volumes starting with 1. This option is useful when the operator
does not know on which volume the files to be extracted are
and/or when he prefers the longer unattended mode rather than
the shorter interactive mode.
-A archive_file
Read the table of contents from archive_file instead of the
media. This option can be used in combination with the -t, -i,
or -x options, making it possible to check whether files are on
the media without having to mount the media.
-b blocksize
The number of kilobytes per dump record. If the -b option is not
specified, restore tries to determine the media block size
dynamically.
-c Normally, restore will try to determine dynamically whether the
dump was made from an old (pre-4.4) or new format file system.
The -c flag disables this check, and only allows reading a dump
in the old format.
-d The -d (debug) flag causes restore to print debug information.
-D filesystem
The -D flag allows the user to specify the filesystem name when
using restore with the -C option to check the backup.
-f file
Read the backup from file; file may be a special device file
like /dev/st0 (a tape drive), /dev/sda1 (a disk drive), an ordi-
nary file, or - (the standard input). If the name of the file is
of the form host:file or user@host:file, restore reads from the
named file on the remote host using rmt(8).
-F script
Run script at the beginning of each tape. The device name and
the current volume number are passed on the command line. The
script must return 0 if restore should continue without asking
the user to change the tape, 1 if restore should continue but
ask the user to change the tape. Any other exit code will cause
restore to abort. For security reasons, restore reverts back to
the real user ID and the real group ID before running the
script.
-h Extract the actual directory, rather than the files that it ref-
erences. This prevents hierarchical restoration of complete sub-
trees from the dump.
-H hash_size
Use a hashtable having the specified number of entries for stor-
ing the directories entries instead of a linked list. This
hashtable will considerably speed up inode lookups (visible
especially in interactive mode when adding/removing files from
the restore list), but at the price of much more memory usage.
The default value is 1, meaning no hashtable is used.
-k Use Kerberos authentication when contacting the remote tape
server. (Only available if this options was enabled when restore
was compiled.)
-l When doing remote restores, assume the remote file is a regular
file (instead of a tape device). If you’re restoring a remote
compressed file, you will need to specify this option or restore
will fail to access it correctly.
-L limit
The -L flag allows the user to specify a maximal number of mis-
compares when using restore with the -C option to check the
backup. If this limit is reached, restore will abort with an
error message. A value of 0 (the default value) disables the
check.
-m Extract by inode numbers rather than by file name. This is use-
ful if only a few files are being extracted, and one wants to
avoid regenerating the complete pathname to the file.
-M Enables the multi-volume feature (for reading dumps made using
the -M option of dump). The name specified with -f is treated as
a prefix and restore tries to read in sequence from 001,
002 etc.
-N The -N flag causes restore to perform a full execution as
requested by one of -i, -R, -r, t or x command without actually
writing any file on disk.
-o The -o flag causes restore to automatically restore the current
directory permissions without asking the operator whether to do
so in one of -i or -x modes.
-Q file
Use the file file in order to read tape position as stored using
the dump Quick File Access mode, in one of -i, -x or -t mode.
It is recommended to set up the st driver to return logical tape
positions rather than physical before calling dump/restore with
parameter -Q. Since not all tape devices support physical tape
positions those tape devices return an error during dump/restore
when the st driver is set to the default physical setting.
Please see the st(4) man page, option MTSETDRVBUFFER , or the
mt(1) man page, on how to set the driver to return logical tape
positions.
Before calling restore with parameter -Q, always make sure the
st driver is set to return the same type of tape position used
during the call to dump. Otherwise restore may be confused.
This option can be used when restoring from local or remote
tapes (see above) or from local or remote files.
-s fileno
Read from the specified fileno on a multi-file tape. File num-
bering starts at 1.
-T directory
The -T flag allows the user to specify a directory to use for
the storage of temporary files. The default value is /tmp. This
flag is most useful when restoring files after having booted
from a floppy. There might be little or no space on the floppy
filesystem, but another source of space might exist.
-u When creating certain types of files, restore may generate a
warning diagnostic if they already exist in the target direc-
tory. To prevent this, the -u (unlink) flag causes restore to
remove old entries before attempting to create new ones.
-v Normally restore does its work silently. The -v (verbose) flag
causes it to type the name of each file it treats preceded by
its file type.
-V Enables reading multi-volume non-tape mediums like CDROMs.
-X filelist
Read list of files to be listed or extracted from the text file
filelist in addition to those specified on the command line.
This can be used in conjunction with the -t or -x commands. The
file filelist should contain file names separated by newlines.
filelist may be an ordinary file or - (the standard input).
-y Do not ask the user whether to abort the restore in the event of
an error. Always try to skip over the bad block(s) and con-
tinue.
(The 4.3BSD option syntax is implemented for backward compatibility but
is not documented here.)
DIAGNOSTICS
Complains if it gets a read error. If y has been specified, or the user
responds y, restore will attempt to continue the restore.
If a backup was made using more than one tape volume, restore will
notify the user when it is time to mount the next volume. If the -x or
-i flag has been specified, restore will also ask which volume the user
wishes to mount. The fastest way to extract a few files is to start
with the last volume, and work towards the first volume.
There are numerous consistency checks that can be listed by restore.
Most checks are self-explanatory or can “never happen”. Common errors
are given below:
Converting to new file system format
A dump tape created from the old file system has been loaded. It
is automatically converted to the new file system format.
: not found on tape
The specified file name was listed in the tape directory, but
was not found on the tape. This is caused by tape read errors
while looking for the file, and from using a dump tape created
on an active file system.
expected next file , got
A file that was not listed in the directory showed up. This can
occur when using a dump created on an active file system.
Incremental dump too low
When doing an incremental restore, a dump that was written
before the previous incremental dump, or that has too low an
incremental level has been loaded.
Incremental dump too high
When doing an incremental restore, a dump that does not begin
its coverage where the previous incremental dump left off, or
that has too high an incremental level has been loaded.
Tape read error while restoring
Tape read error while skipping over inode
Tape read error while trying to resynchronize
A tape (or other media) read error has occurred. If a file name
is specified, its contents are probably partially wrong. If an
inode is being skipped or the tape is trying to resynchronize,
no extracted files have been corrupted, though files may not be
found on the tape.
resync restore, skipped blocks
After a dump read error, restore may have to resynchronize
itself. This message lists the number of blocks that were
skipped over.
EXIT STATUS
Restore exits with zero status on success. Tape errors are indicated
with an exit code of 1.
When doing a comparison of files from a dump, an exit code of 2 indi-
cates that some files were modified or deleted since the dump was made.
ENVIRONMENT
If the following environment variable exists it will be utilized by
restore:
TAPE If no -f option was specified, restore 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.
TMPDIR The directory given in TMPDIR will be used instead of /tmp to
store temporary files.
RMT The environment variable RMT will be used to determine the path-
name of the remote rmt(8) program.
RSH Restore uses the contents of this variable to determine the name
of the remote shell command to use when doing a network restore
(rsh, ssh etc.). If this variable is not set, rcmd(3) will be
used, but only root will be able to do a network restore.
FILES
/dev/st0
the default tape drive
/tmp/rstdir*
file containing directories on the tape
/tmp/rstmode*
owner, mode, and time stamps for directories
./restoresymtable
information passed between incremental restores
SEE ALSO
dump(8), mount(8), mke2fs(8), rmt(8)
BUGS
Restore can get confused when doing incremental restores from dumps
that were made on active file systems.
A level 0 dump must be done after a full restore. Because restore runs
in user code, it has no control over inode allocation; thus a full dump
must be done to get a new set of directories reflecting the new inode
numbering, even though the content of the files is unchanged.
The temporary files /tmp/rstdir* and /tmp/rstmode* are generated with a
unique name based on the date of the dump and the process ID (see
mktemp(3)), except when -r or -R is used. Because -R allows you to
restart a -r operation that may have been interrupted, the temporary
files should be the same across different processes. In all other
cases, the files are unique because it is possible to have two differ-
ent dumps started at the same time, and separate operations shouldn’t
conflict with each other.
To do a network restore, you have to run restore as root or use a
remote shell replacement (see RSH variable). This is due to the previ-
ous security history of dump and restore. ( restore is written to be
setuid root, but we are not certain all bugs are gone from the code -
run setuid at your own risk.)
At the end of restores in -i or -x modes (unless -o option is in use),
restore will ask the operator whether to set the permissions on the
current directory. If the operator confirms this action, the permis-
sions on the directory from where restore was launched will be replaced
by the permissions on the dumped root inode. Although this behaviour is
not really a bug, it has proven itself to be confusing for many users,
so it is recommended to answer ’no’, unless you’re performing a full
restore and you do want to restore the permissions on ’/’.
It should be underlined that because it runs in user code, restore ,
when run with the -C option, sees the files as the kernel presents
them, whereas dump sees all the files on a given filesystem. In partic-
ular, this can cause some confusion when comparing a dumped filesystem
a part of which is hidden by a filesystem mounted on top of it.
AUTHOR
The dump/restore backup suite was ported to Linux’s Second Extended
File System by Remy Card . He maintained the initial
versions of dump (up and including 0.4b4, released in January 1997).
Starting with 0.4b5, the new maintainer is Stelian Pop
.
AVAILABILITY
The dump/restore backup suite is available from
HISTORY
The restore command appeared in 4.2BSD.
BSD version 0.4b41 of January 2, 2006 RESTORE(8)
3 RMT的linux_Manual:
[root@embedded disk]# man rmt | cat
RMT(8) System management commands RMT(8)
NAME
rmt - remote magtape protocol module
SYNOPSIS
rmt
DESCRIPTION
Rmt is a program used by the remote dump(8), restore(8) or tar(1) pro-
grams in manipulating a magnetic tape drive through an interprocess
communication connection. Rmt is normally started up with an rexec(3)
or rcmd(3) call.
The rmt program accepts requests specific to the manipulation of mag-
netic tapes, performs the commands, then responds with a status indica-
tion. All responses are in ASCII and in one of the following two
forms.
Successful commands have responses of:
Anumber\n
where number is an ASCII representation of a decimal number.
Unsuccessful commands are responded to with:
Eerror-number\nerror-message\n
where error-number is one of the possible error numbers described in
intro(2) and error-message is the corresponding error string as printed
from a call to perror(3).
The protocol is comprised of the following commands, which are sent as
indicated - no spaces are supplied between the command and its argu-
ments, or between its arguments, and \n indicates that a newline should
be supplied:
Odevice\nmode\n
Open the specified device using the indicated mode. Device is a
full pathname and mode is an ASCII representation of a decimal
number suitable for passing to open(2). If a device had already
been opened, it is closed before a new open is performed.
Cdevice\n
Close the currently open device. The device specified is
ignored.
Lwhence\noffset\n
Perform an lseek(2) operation using the specified parameters.
The response value is that returned from the lseek call.
Wcount\n
Write data onto the open device. Rmt reads count bytes from the
connection, aborting if a premature end-of-file is encountered.
The response value is that returned from the write(2) call.
Rcount\n
Read count bytes of data from the open device. If count exceeds
the size of the data buffer (10 kilobytes), it is truncated to
the data buffer size. Rmt then performs the requested read(2)
and responds with Acount-read\n if the read was successful; oth-
erwise an error in the standard format is returned. If the read
was successful, the data read is then sent.
Ioperation\ncount\n
Perform a MTIOCOP ioctl(2) command using the specified parame-
ters. The parameters are interpreted as the ASCII
representations of the decimal values to place in the mt_op and
mt_count fields of the structure used in the ioctl call. The
return value is the count parameter when the operation is suc-
cessful.
By issuing the I-1\n0\n command, a client will specify that he
is using the VERSION 1 protocol.
For a VERSION 0 client, the operation parameter is the platform
mt_op value (could be different if the client and the rmt server
are on two different platforms). For a VERSION 1 client, the
operation parameter is standardized as below:
0 Issue a MTWEOF command (write count end-of-file records).
1 Issue a MTFSF command (forward space over count file
marks).
2 Issue a MTBSF command (backward space over count file
marks).
3 Issue a MTFSR command (forward space count inter-record
gaps).
4 Issue a MTBSR command (backward space count inter-record
gaps).
5 Issue a MTREW command (rewind).
6 Issue a MTOFFL command (rewind and put the drive
offline).
7 Issue a MTNOP command (no operation, set status only).
ioperation\ncount\n
Perform an extended MTIOCOP ioctl(2) command using the specified
parameters. The parameters are interpreted as the ASCII repre-
sentations of the decimal values to place in the mt_op and
mt_count fields of the structure used in the ioctl call. The
return value is the count parameter when the operation is suc-
cessful. The possible operations are:
0 Issue a MTCACHE command (switch cache on).
1 Issue a MTNOCACHE command (switch cache off).
2 Issue a MTRETEN command (retension the tape).
3 Issue a MTERASE command (erase the entire tape).
4 Issue a MTEOM command (position to end of media).
5 Issue a MTNBSF command (backward space count files to
BOF).
S Return the status of the open device, as obtained with a MTI-
OCGET ioctl call. If the operation was successful, an “ack” is
sent with the size of the status buffer, then the status buffer
is sent (in binary, which is non-portable between different
platforms).
ssub-command
This is a replacement for the previous S command, portable
across different platforms. If the open device is a magnetic
tape, return members of the magnetic tape status structure, as
obtained with a MTIOCGET ioctl call. If the open device is not a
magnetic tape, an error is returned. If the MTIOCGET operation
was successful, the numerical value of the structure member is
returned in decimal. The following sub commands are supported:
T return the content of the structure member mt_type which
contains the type of the magnetic tape device.
D return the content of the structure member mt_dsreg which
contains the "drive status register".
E return the content of the structure member mt_erreg which
contains the "error register". This structure member must
be retrieved first because it is cleared after each MTI-
OCGET ioctl call.
R return the content of the structure member mt_resid which
contains the residual count of the last I/O.
F return the content of the structure member mt_fileno
which contains the file number of the current tape posi-
tion.
B return the content of the structure member mt_blkno which
contains the block number of the current tape position.
f return the content of the structure member mt_flags which
contains MTF_ flags from the driver.
b return the content of the structure member mt_bf which
contains the optimum blocking factor.
Any other command causes rmt to exit.
DIAGNOSTICS
All responses are of the form described above.
SEE ALSO
rcmd(3), rexec(3), /usr/include/sys/mtio.h, rdump(8), rrestore(8)
BUGS
People should be discouraged from using this for a remote file access
protocol.
AUTHOR
The dump/restore backup suit was ported to Linux’s Second Extended File
System by Remy Card . He maintained the initial ver-
sions of dump (up and including 0.4b4, released in january 1997).
Starting with 0.4b5, the new maintainer is Stelian Pop
.
AVAILABILITY
The dump/restore backup suit is available from
HISTORY
The rmt command appeared in 4.2BSD.
BSD version 0.4b41 of January 2, 2006 RMT(8)
[root@embedded disk]#