NAME¶

paxtar — tape archiver

SYNOPSIS¶

DESCRIPTION¶

The paxtar command creates, adds files to, or extracts files from an archive file in “tar” (strictly speaking, ustar) format. A tar archive is often stored on a magnetic tape, but can be stored equally well on a floppy, CD-ROM, or in a regular disk file.

In the first (legacy) form, all option flags except for -C and -I must be contained within the first argument to paxtar and must not be prefixed by a hyphen (‘-’). Option arguments, if any, are processed as subsequent arguments to paxtar and are processed in the order in which their corresponding option flags have been presented on the command line.

In the second and preferred form, option flags may be given in any order and are immediately followed by their corresponding option argument values.

One of the following flags must be present:

-c

Create new archive, or overwrite an existing archive, adding the specified files to it.

-r

Append the named new files to existing archive. Note that this will only work on media on which an end-of-file mark can be overwritten.

-t

List contents of archive. If any files are named on the command line, only those files will be listed. The file arguments may be specified as glob patterns (see glob(7) for more information), in which case paxtar will list all archive members that match each pattern.

-u

Alias for -r.

-x

Extract files from archive. If any files are named on the command line, only those files will be extracted from the archive. The file arguments may be specified as glob patterns (see glob(7) for more information), in which case paxtar will extract all archive members that match each pattern.

If more than one copy of a file exists in the archive, later copies will overwrite earlier copies during extraction. The file mode and modification time are preserved if possible. The file mode is subject to modification by the umask(2).

In addition to the flags mentioned above, any of the following flags may be used:

-a

Guess the compression utility based on the archive filename. Inability to guess will result in quietly not using any compression. This option only exists for semi-compatibility with GNU tar; it is strongly recommended to archive to stdout and pipe into an external compression utility with appropriate arguments instead:

tar -cf - foo | xz -2e >foo.txz

-b blocking-factor

Set blocking factor to use for the archive. paxtar uses 512-byte blocks. The default is 20, the maximum is 126. Archives with a blocking factor larger than 63 violate the POSIX standard and will not be portable to all systems.

-C directory

This is a positional argument which sets the working directory for the following files. When extracting, files will be extracted into the specified directory; when creating, the specified files will be matched from the directory.

-D format-options

Specify the archive format and format options, separated by comma. paxtar currently supports the following formats and options:

ar

The Unix Archiver library format. This format matches APT repositories and the BSD ar(1) specification, not GNU binutils (which can however read them) or SYSV systems. See ar(5) on some operating systems for more information.

bcpio

The old binary cpio format. The default blocksize for this format is 5120 bytes. This format is not very portable and should not be used when other formats are available. Inode and device information about a file (used for detecting file hard links by this format), which may be truncated by this format, is detected by paxtar and is repaired.

cpio

The extended cpio interchange format specified in the IEEE Std 1003.2 (“POSIX.2”) standard. The default blocksize for this format is 5120 bytes. Inode and device information about a file (used for detecting file hard links by this format), which may be truncated by this format, is detected by paxtar and is repaired.

sv4cpio

The System V release 4 cpio. The default blocksize for this format is 5120 bytes. Inode and device information about a file (used for detecting file hard links by this format), which may be truncated by this format, is detected by paxtar and is repaired.

sv4crc

The System V release 4 cpio with file CRC checksums. The default blocksize for this format is 5120 bytes. Inode and device information about a file (used for detecting file hard links by this format), which may be truncated by this format, is detected by paxtar and is repaired.

tar

The old BSD tar format as found in 4.3BSD. The default blocksize for this format is 10240 bytes. Pathnames stored by this format must be 100 characters or less in length. Only regular files, hard links, soft links, and directories will be archived (other filesystem types are not supported).

For backwards compatibility with even older tar formats, the write_opt=nodir option can be used when writing an archive to omit the storage of directories.

ustar

The extended tar interchange format specified in the IEEE Std 1003.2 (“POSIX.2”) standard. The default blocksize for this format is 10240 bytes. Filenames stored by this format must be 100 characters or less in length; the total pathname must be 256 characters or less.

paxtar will detect and report any file that it is unable to store or extract as the result of any specific archive format restrictions. The individual archive formats may impose additional restrictions on use. Typical archive format restrictions include (but are not limited to): file pathname length, file size, link pathname length, and the type of the file.

-e

Stop after the first error.

-f archive

Filename where the archive is stored. Defaults to /dev/rst0. If set to hyphen (‘-’) standard output is used. See also the TAPE environment variable.

-H

Follow symlinks given on the command line only.

-h

Follow symbolic links as if they were normal files or directories. In extract mode this means that a directory entry in the archive will not overwrite an existing symbolic link, but rather what the link ultimately points to.

-I file

This is a positional argument which reads the names of files to archive or extract from the given file, one per line.

-J

Use the xz utility to compress the archive.

-j

Use the bzip2 utility to compress the archive.

-L

Synonym for the -h option.

-M flag

Configure the archive normaliser. flag is either a numeric value compatible to strtonum(3) which is directly stored in the flags word, or one of the following values, optionally prefixed with “no-” to turn them off:

inodes

0x0001: Serialise inodes, zero device info.
(cpio, sv4cpio, sv4crc)

links

0x0002: Store content of hard links only once.
(cpio, sv4cpio, sv4crc)

mtime

0x0004: Zero out the file modification time.
(ar, cpio, sv4cpio, sv4crc, ustar)

uidgid

0x0008: Set owner to 0:0 (root:wheel).
(ar, cpio, sv4cpio, sv4crc, ustar)

verb

0x0010: Debug this option.

debug

0x0020: Debug file header storage.

lncp

0x0040: Extract hard links by copy if link fails.

numid

0x0080: Use only numeric uid and gid values.
(ustar)

gslash

0x0100: Append a slash after directory names.
(ustar)

set

0x0003: Keep ownership and mtime intact.

dist

0x008B: Clean everything except mtime.

norm

0x008F: Clean everything.

root

0x0089: Clean owner and device information.

When creating an archive and verbosely listing output, these normalisation operations are not reflected in the output, because they are made only after the output has been shown.

This option is only implemented for the ar, cpio, sv4cpio, sv4crc, and ustar file format writing routines.

-m

Do not preserve modification time.

-O

If reading, extract files to standard output.
If writing, write old-style (non-POSIX) archives.

-o

If writing, write old-style (non-POSIX) archives.
Don't write directory information that the older (V7) style tar is unable to decode. Same as -D tar,write_opt=nodir.

-P

For security reasons, paxtar skips pathnames containing dotdot (“..”) components and strips leading slashes (‘/’) from pathnames by default; this option disables that behaviour.

-p

Preserve user and group ID as well as file mode regardless of the current umask(2). The setuid and setgid bits are only preserved if the user and group ID could be preserved. Only meaningful in conjunction with the -x flag.

-q

Select the first archive member that matches each file operand. No more than one archive member is matched for each file. When members of type directory are matched, the file hierarchy rooted at that directory is also matched.

-s replstr

Modify the archive member names according to the substitution expression replstr, using the syntax of the ed(1) utility regular expressions. file arguments may be given to restrict the list of archive members to those specified.

The format of these regular expressions is

/old/new/[gp]

As in ed(1), old is a basic regular expression (see re_format(7)) and new can contain an ampersand (‘&’), ‘\n’ (where n is a digit) back-references, or subexpression matching. The old string may also contain newline characters. Any non-null character can be used as a delimiter (‘/’ is shown here). Multiple -s expressions can be specified. The expressions are applied in the order they are specified on the command line, terminating with the first successful substitution.

The optional trailing g continues to apply the substitution expression to the pathname substring, which starts with the first character following the end of the last successful substitution. The first unsuccessful substitution stops the operation of the g option. The optional trailing p will cause the final result of a successful substitution to be written to standard error in the following format:

original-pathname >> new-pathname

File or archive member names that substitute to the empty string are not selected and will be skipped.

-v

Verbose operation mode. If -v is specified multiple times or if the -t option is also specified, paxtar will use a long format for listing files, similar to ls(1) -l.

-w

Interactively rename files. This option causes paxtar to prompt the user for the filename to use when storing or extracting files in an archive.

-X

Do not cross mount points in the filesystem.

-Z

Use the compress(1) utility to compress the archive.

-z

Use the gzip(1) utility to compress the archive.

The options [-014578] can be used to select one of the compiled-in backup devices, /dev/rstN.

ENVIRONMENT¶

TMPDIR

Path in which to store temporary files.

TAPE

Default tape device to use instead of /dev/rst0. If set to hyphen (‘-’) standard output is used.

FILES¶

/dev/rst0

default archive name

EXIT STATUS¶

The paxtar utility exits with one of the following values:

EXAMPLES¶

Create an archive on the default tape drive, containing the files named bonvole and sekve:

Output a gzip(1) compressed archive containing the files bonvole and sekve to a file called foriru.tar.gz:

Verbosely create an archive, called backup.tar.gz, of all files matching the shell glob(7) function *.c:

Verbosely list, but do not extract, all files ending in .jpeg from a compressed archive named backup.tar.gz. Note that the glob pattern has been quoted to avoid expansion by the shell:

For more detailed examples, see pax(1).

DIAGNOSTICS¶

Whenever paxtar cannot create a file or a link when extracting an archive or cannot find a file while writing an archive, or cannot preserve the user ID, group ID, file mode, or access and modification times when the -p option is specified, a diagnostic message is written to standard error and a non-zero exit value will be returned, but processing will continue. In the case where paxtar cannot create a link to a file, unless -M lncp is given, paxtar will not create a second copy of the file.

If the extraction of a file from an archive is prematurely terminated by a signal or error, paxtar may have only partially extracted the file the user wanted. Additionally, the file modes of extracted files and directories may have incorrect file bits, and the modification and access times may be wrong.

If the creation of an archive is prematurely terminated by a signal or error, paxtar may have only partially created the archive, which may violate the specific archive format specification.

SEE ALSO¶

ar(1), cpio(1), pax(1), paxcpio(1), tar(1), deb(5)

HISTORY¶

A tar command first appeared in Version 7 AT&T UNIX.

AUTHORS¶

Keith Muller at the University of California, San Diego. MirBSD extensions by mirabilos ⟨m@mirbsd.org⟩.

CAVEATS¶

The flags -aDJjLMo are not portable to other implementations of tar where they may have a different meaning or not exist at all.

This implementation may have support for other non-standard options that are undocumented because removal-inducing deprecation was issued.

BUGS¶

The pax file format is not yet supported.