mdtar(1)mdtar(1)Namemdtar - multivolume archiver
Syntaxmdtar [key] [name...]
The command saves multiple files on multiple archives (usually an
RX50 diskette, but any file/device may be specified). actions are con‐
trolled by the key argument. The key is a string of characters con‐
taining one function letter and one or more function modifiers. Other
arguments to are file or directory names specifying which files to dump
or restore. In all cases, appearance of a directory name refers to the
files and, recursively, subdirectories of that directory. also saves
This utility supports EOT handling which allows the use of multiple
media. The utility prompts for the next volume when it encounters the
end of the current volume.
This utility supports the TA90 style sequential stacker loader device.
The device ejects a cartridge when it is taken off line. This utility
performs the device ejection on behalf of the user when it encounters a
multivolume boundary during write or read operations involving tape.
The device then automatically loads the next available tape (if there
is one). The utility then attempts to access this next tape for a rea‐
sonable amount of time (approximately three minutes) before prompting
the user for a manual reload operation.
Options-C Changes directory to specified name. This allows multiple
directories not related by a close common parent, to be
archived using short relative path names. For example, to
archive files from and from one might use
mdtar c -C /usr include . -C /etc .
The function portion of the key is specified by a letter.
c Creates a new archive. Writing begins at the beginning of
the archive instead of after the last file.
r Writes the named files to the end of the archive.
t Generates archive table of contents. If no argument is
given, all of the names on the archive are listed.
u Updates the current archive. Adds the named files to the ar‐
chive, if they are not there already or if they have been
modified since last put on the archive.
x Extracts each specified file from the archive. If the named
file matches a directory whose contents had been written onto
the archive, this directory is recursively extracted. The
owner, modification time, and mode are restored if you are
the superuser and if you have also specified the p switch.
If no file argument is given, the entire content of the ar‐
chive is extracted. If multiple entries specifying the same
file are on the archive, the last one overwrites previous
The following characters may be used to qualify the function desired in
addition to one or more of the above letters.
0...9 Selects unit number of the drive as an alternate disk drive.
The default disk drive is the device named
A Uses the specified number (next argument) as archive with
which to begin the output. This switch is intended for error
recovery. outputs files in terms of Archives. Each Archive
contains a number of files. If has been requested to dump a
path (set of files) that consist of (for example) 10 archives
and there is an error writing the nth Archive, then the A
modifier may be used to restart at the nth Archive. You must
issue the same path (set of files) as in the first command.
This will guarantee that will begin at the correct file on
Archive n. If the v mode is specified, outputs informational
messages to inform the user of progress. For example, the
following command will dump the entire directory structure:
If an error occurs on Archive 7, to restart at the 7th Ar‐
chive, without having to re-dump the first 6 Archives, issue
the following command:
mdtar cvA 7
will tell you it is skipping the first 6 Archives and will
resume output with the data that begins Archive 7.
b Uses the specified number (next argument) as the blocking
factor. The default is 20 (the maximum is 20).
B Forces output blocking to 20 blocks per record.
f Uses the specified file (next argument) as the name of the
archive. If the name of the file is -, writes to standard
F[fR] Operates in fast mode. When F is specified, skips all SCCS
directories, core files, and errs files. When FF is speci‐
fied, also skips all a.out and *.o files.
h Saves a copy of the file (excludes symbolic links). The
default action of is to place symbolic link information on
the output device. A copy of the file IS NOT saved on the
i Ignores checksum errors found in the archive.
l Displays an error message if all links to the files dumped
cannot be resolved. If -l is not specified, no error messages
L Permits the program to treat the tape drive as a sequential
loader device even though it is not represented as such in
the system driver tables.
m Does not restore file modification times. The modification
time is the time of extraction. Normally, restores modifica‐
tion times of regular and special files.
o Suppresses the normal directory information. On output, nor‐
mally places information specifying owner and modes of direc‐
tories in the archive. Former versions of when encountering
this information will give the error message
<name>/: cannot create.
p Restores the named files to their original modes, ignoring
the present Setuid and sticky information will also be
restored to the super-user. You must be Superuser to perform
this option. For further information, see S_ISVTX.
s Uses specified number (next argument) as size of media in
512-byte blocks. This enables to be used with devices of
different physical media sizes. The default is 800 blocks
(assumption is an RX50 output Archive).
v Displays detailed (verbose) information as it archives files.
Normally does its work silently. With the t function, the
verbose option gives more information about the archive
entries than just their names.
#mdtar cvf mdtar-out vmunix
Produces the output ``a vmunix 1490 blocks'' where 1490 is
the number of 512 byte blocks in the file ``vmunix''.
#mdtar xvf mdtar-out
Produces the output ``x vmunix, 762880 bytes, 1490 blocks''
where 762880 is the number of bytes and 1490 is the number of
512 byte blocks in the file ``vmunix'' which was extracted.
w Displays action to be taken for each file and prompts for
confirmation. If a word beginning with `y' is given, the
action is done. Any other input means do not do it.
The u option can be slow.
The current limit on file name length is 100 characters.
There is no way to follow symbolic links selectively.
On SCSI tape devices tar (when reading) may end on one volume of a mul‐
tivolume set without prompting for the next volume. This is a very
infrequent condition. The next volume should be loaded and the command
Using a blocking factor other than the default (b option) may lead to
higher performance. However, you must select a value that is compati‐
ble with the hardware limitations of the source and destination
machines. Software limitations may apply for other versions of
When extracting (x), reads the entire tape. See the r and u keys.
The u and the r function keys do not operate with quarter-inch tape
cartidge drives such as the TZK10.
ULTRIX due to BSD coding, does not completely fill a flexible disc in
In multivolulme situations, ULTRIX employs the following header rules
for volume-spanning files. At the beginning of the next volume, a sec‐
ond header is written that includes both the full size of the file and
the size of the file segment that is written on the second volume. The
first header states the full size of the file only. These rules may
not be compatible with other systems' versions of
Indicates bad key characters and archive read/write errors.
Indicates if enough memory is not available to hold the link tables.
FilesSee Alsostat(2), tar(1)mdtar(1)