TAR(5)			    BSD File Formats Manual			TAR(5)

NAME

     tar — format of tape archive files

DESCRIPTION

     The tar archive format collects any number of files, directories, and

     other file system objects (symbolic links, device nodes, etc.) into a

     single stream of bytes.  The format was originally designed to be used

     with tape drives that operate with fixed-size blocks, but is widely used

     as a general packaging mechanism.

   General Format

     A tar archive consists of a series of 512-byte records.  Each file system

     object requires a header record which stores basic metadata (pathname,

     owner, permissions, etc.) and zero or more records containing any file

     data.  The end of the archive is indicated by two records consisting

     entirely of zero bytes.

     For compatibility with tape drives that use fixed block sizes, programs

     that read or write tar files always read or write a fixed number of

     records with each I/O operation.  These “blocks” are always a multiple of

     the record size.  The maximum block size supported by early implementa‐

     tions was 10240 bytes or 20 records.  This is still the default for most

     implementations although block sizes of 1MiB (2048 records) or larger are

     commonly used with modern high-speed tape drives.	(Note: the terms

     “block” and “record” here are not entirely standard; this document fol‐

     lows the convention established by John Gilmore in documenting pdtar.)

   Old-Style Archive Format

     The original tar archive format has been extended many times to include

     additional information that various implementors found necessary.	This

     section describes the variant implemented by the tar command included in

     Version 7 AT&T UNIX, which seems to be the earliest widely-used version

     of the tar program.

     The header record for an old-style tar archive consists of the following:

	   struct header_old_tar {

		   char name[100];

		   char mode[8];

		   char uid[8];

		   char gid[8];

		   char size[12];

		   char mtime[12];

		   char checksum[8];

		   char linkflag[1];

		   char linkname[100];

		   char pad[255];

	   };

     All unused bytes in the header record are filled with nulls.

     name    Pathname, stored as a null-terminated string.  Early tar imple‐

	     mentations only stored regular files (including hardlinks to

	     those files).  One common early convention used a trailing "/"

	     character to indicate a directory name, allowing directory per‐

	     missions and owner information to be archived and restored.

     mode    File mode, stored as an octal number in ASCII.

     uid, gid

	     User id and group id of owner, as octal numbers in ASCII.

     size    Size of file, as octal number in ASCII.  For regular files only,

	     this indicates the amount of data that follows the header.  In

	     particular, this field was ignored by early tar implementations

	     when extracting hardlinks.  Modern writers should always store a

	     zero length for hardlink entries.

     mtime   Modification time of file, as an octal number in ASCII.  This

	     indicates the number of seconds since the start of the epoch,

	     00:00:00 UTC January 1, 1970.  Note that negative values should

	     be avoided here, as they are handled inconsistently.

     checksum

	     Header checksum, stored as an octal number in ASCII.  To compute

	     the checksum, set the checksum field to all spaces, then sum all

	     bytes in the header using unsigned arithmetic.  This field should

	     be stored as six octal digits followed by a null and a space

	     character.  Note that many early implementations of tar used

	     signed arithmetic for the checksum field, which can cause inter‐

	     operability problems when transferring archives between systems.

	     Modern robust readers compute the checksum both ways and accept

	     the header if either computation matches.

     linkflag, linkname

	     In order to preserve hardlinks and conserve tape, a file with

	     multiple links is only written to the archive the first time it

	     is encountered.  The next time it is encountered, the linkflag is

	     set to an ASCII ‘1’ and the linkname field holds the first name

	     under which this file appears.  (Note that regular files have a

	     null value in the linkflag field.)

     Early tar implementations varied in how they terminated these fields.

     The tar command in Version 7 AT&T UNIX used the following conventions

     (this is also documented in early BSD manpages): the pathname must be

     null-terminated; the mode, uid, and gid fields must end in a space and a

     null byte; the size and mtime fields must end in a space; the checksum is

     terminated by a null and a space.	Early implementations filled the

     numeric fields with leading spaces.  This seems to have been common prac‐

     tice until the IEEE Std 1003.1-1988 (“POSIX.1”) standard was released.

     For best portability, modern implementations should fill the numeric

     fields with leading zeros.

   Pre-POSIX Archives

     An early draft of IEEE Std 1003.1-1988 (“POSIX.1”) served as the basis

     for John Gilmore's pdtar program and many system implementations from the

     late 1980s and early 1990s.  These archives generally follow the POSIX

     ustar format described below with the following variations:

     ·	     The magic value consists of the five characters “ustar” followed

	     by a space.  The version field contains a space character fol‐

	     lowed by a null.

     ·	     The numeric fields are generally filled with leading spaces (not

	     leading zeros as recommended in the final standard).

     ·	     The prefix field is often not used, limiting pathnames to the 100

	     characters of old-style archives.

   POSIX ustar Archives

     IEEE Std 1003.1-1988 (“POSIX.1”) defined a standard tar file format to be

     read and written by compliant implementations of tar(1).  This format is

     often called the “ustar” format, after the magic value used in the

     header.  (The name is an acronym for “Unix Standard TAR”.)  It extends

     the historic format with new fields:

	   struct header_posix_ustar {

		   char name[100];

		   char mode[8];

		   char uid[8];

		   char gid[8];

		   char size[12];

		   char mtime[12];

		   char checksum[8];

		   char typeflag[1];

		   char linkname[100];

		   char magic[6];

		   char version[2];

		   char uname[32];

		   char gname[32];

		   char devmajor[8];

		   char devminor[8];

		   char prefix[155];

		   char pad[12];

	   };

     typeflag

	     Type of entry.  POSIX extended the earlier linkflag field with

	     several new type values:

	     “0”     Regular file.  NUL should be treated as a synonym, for

		     compatibility purposes.

	     “1”     Hard link.

	     “2”     Symbolic link.

	     “3”     Character device node.

	     “4”     Block device node.

	     “5”     Directory.

	     “6”     FIFO node.

	     “7”     Reserved.

	     Other   A POSIX-compliant implementation must treat any unrecog‐

		     nized typeflag value as a regular file.  In particular,

		     writers should ensure that all entries have a valid file‐

		     name so that they can be restored by readers that do not

		     support the corresponding extension.  Uppercase letters

		     "A" through "Z" are reserved for custom extensions.  Note

		     that sockets and whiteout entries are not archivable.

	     It is worth noting that the size field, in particular, has dif‐

	     ferent meanings depending on the type.  For regular files, of

	     course, it indicates the amount of data following the header.

	     For directories, it may be used to indicate the total size of all

	     files in the directory, for use by operating systems that pre-

	     allocate directory space.	For all other types, it should be set

	     to zero by writers and ignored by readers.

     magic   Contains the magic value “ustar” followed by a NUL byte to indi‐

	     cate that this is a POSIX standard archive.  Full compliance

	     requires the uname and gname fields be properly set.

     version

	     Version.  This should be “00” (two copies of the ASCII digit

	     zero) for POSIX standard archives.

     uname, gname

	     User and group names, as null-terminated ASCII strings.  These

	     should be used in preference to the uid/gid values when they are

	     set and the corresponding names exist on the system.

     devmajor, devminor

	     Major and minor numbers for character device or block device

	     entry.

     name, prefix

	     If the pathname is too long to fit in the 100 bytes provided by

	     the standard format, it can be split at any / character with the

	     first portion going into the prefix field.  If the prefix field

	     is not empty, the reader will prepend the prefix value and a /

	     character to the regular name field to obtain the full pathname.

	     The standard does not require a trailing / character on directory

	     names, though most implementations still include this for compat‐

	     ibility reasons.

     Note that all unused bytes must be set to NUL.

     Field termination is specified slightly differently by POSIX than by pre‐

     vious implementations.  The magic, uname, and gname fields must have a

     trailing NUL.  The pathname, linkname, and prefix fields must have a

     trailing NUL unless they fill the entire field.  (In particular, it is

     possible to store a 256-character pathname if it happens to have a / as

     the 156th character.)  POSIX requires numeric fields to be zero-padded in

     the front, and requires them to be terminated with either space or NUL

     characters.

     Currently, most tar implementations comply with the ustar format, occa‐

     sionally extending it by adding new fields to the blank area at the end

     of the header record.

   Numeric Extensions

     There have been several attempts to extend the range of sizes or times

     supported by modifying how numbers are stored in the header.

     One obvious extension to increase the size of files is to eliminate the

     terminating characters from the various numeric fields.  For example, the

     standard only allows the size field to contain 11 octal digits, reserving

     the twelfth byte for a trailing NUL character.  Allowing 12 octal digits

     allows file sizes up to 64 GB.

     Another extension, utilized by GNU tar, star, and other newer tar imple‐

     mentations, permits binary numbers in the standard numeric fields.  This

     is flagged by setting the high bit of the first byte.  The remainder of

     the field is treated as a signed twos-complement value.  This permits

     95-bit values for the length and time fields and 63-bit values for the

     uid, gid, and device numbers.  In particular, this provides a consistent

     way to handle negative time values.  GNU tar supports this extension for

     the length, mtime, ctime, and atime fields.  Joerg Schilling's star pro‐

     gram and the libarchive library support this extension for all numeric

     fields.  Note that this extension is largely obsoleted by the extended

     attribute record provided by the pax interchange format.

     Another early GNU extension allowed base-64 values rather than octal.

     This extension was short-lived and is no longer supported by any imple‐

     mentation.

   Pax Interchange Format

     There are many attributes that cannot be portably stored in a POSIX ustar

     archive.  IEEE Std 1003.1-2001 (“POSIX.1”) defined a “pax interchange

     format” that uses two new types of entries to hold text-formatted meta‐

     data that applies to following entries.  Note that a pax interchange for‐

     mat archive is a ustar archive in every respect.  The new data is stored

     in ustar-compatible archive entries that use the “x” or “g” typeflag.  In

     particular, older implementations that do not fully support these exten‐

     sions will extract the metadata into regular files, where the metadata

     can be examined as necessary.

     An entry in a pax interchange format archive consists of one or two stan‐

     dard ustar entries, each with its own header and data.  The first

     optional entry stores the extended attributes for the following entry.

     This optional first entry has an "x" typeflag and a size field that indi‐

     cates the total size of the extended attributes.  The extended attributes

     themselves are stored as a series of text-format lines encoded in the

     portable UTF-8 encoding.  Each line consists of a decimal number, a

     space, a key string, an equals sign, a value string, and a new line.  The

     decimal number indicates the length of the entire line, including the

     initial length field and the trailing newline.  An example of such a

     field is:

	   25 ctime=1084839148.1212\n

     Keys in all lowercase are standard keys.  Vendors can add their own keys

     by prefixing them with an all uppercase vendor name and a period.	Note

     that, unlike the historic header, numeric values are stored using deci‐

     mal, not octal.  A description of some common keys follows:

     atime, ctime, mtime

	     File access, inode change, and modification times.  These fields

	     can be negative or include a decimal point and a fractional

	     value.

     hdrcharset

	     The character set used by the pax extension values.  By default,

	     all textual values in the pax extended attributes are assumed to

	     be in UTF-8, including pathnames, user names, and group names.

	     In some cases, it is not possible to translate local conventions

	     into UTF-8.  If this key is present and the value is the six-

	     character ASCII string “BINARY”, then all textual values are

	     assumed to be in a platform-dependent multi-byte encoding.  Note

	     that there are only two valid values for this key: “BINARY” or

	     “ISO-IR 10646 2000 UTF-8”.  No other values are permitted by the

	     standard, and the latter value should generally not be used as it

	     is the default when this key is not specified.  In particular,

	     this flag should not be used as a general mechanism to allow

	     filenames to be stored in arbitrary encodings.

     uname, uid, gname, gid

	     User name, group name, and numeric UID and GID values.  The user

	     name and group name stored here are encoded in UTF8 and can thus

	     include non-ASCII characters.  The UID and GID fields can be of

	     arbitrary length.

     linkpath

	     The full path of the linked-to file.  Note that this is encoded

	     in UTF8 and can thus include non-ASCII characters.

     path    The full pathname of the entry.  Note that this is encoded in

	     UTF8 and can thus include non-ASCII characters.

     realtime.*, security.*

	     These keys are reserved and may be used for future standardiza‐

	     tion.

     size    The size of the file.  Note that there is no length limit on this

	     field, allowing conforming archives to store files much larger

	     than the historic 8GB limit.

     SCHILY.*

	     Vendor-specific attributes used by Joerg Schilling's star imple‐

	     mentation.

     SCHILY.acl.access, SCHILY.acl.default, SCHILY.acl.ace

	     Stores the access, default and NFSv4 ACLs as textual strings in a

	     format that is an extension of the format specified by POSIX.1e

	     draft 17.	In particular, each user or group access specification

	     can include an additional colon-separated field with the numeric

	     UID or GID.  This allows ACLs to be restored on systems that may

	     not have complete user or group information available (such as

	     when NIS/YP or LDAP services are temporarily unavailable).

     SCHILY.devminor, SCHILY.devmajor

	     The full minor and major numbers for device nodes.

     SCHILY.fflags

	     The file flags.

     SCHILY.realsize

	     The full size of the file on disk.  XXX explain? XXX

     SCHILY.dev, SCHILY.ino, SCHILY.nlinks

	     The device number, inode number, and link count for the entry.

	     In particular, note that a pax interchange format archive using

	     Joerg Schilling's SCHILY.* extensions can store all of the data

	     from struct stat.

     LIBARCHIVE.*

	     Vendor-specific attributes used by the libarchive library and

	     programs that use it.

     LIBARCHIVE.creationtime

	     The time when the file was created.  (This should not be confused

	     with the POSIX “ctime” attribute, which refers to the time when

	     the file metadata was last changed.)

     LIBARCHIVE.xattr.namespace.key

	     Libarchive stores POSIX.1e-style extended attributes using keys

	     of this form.  The key value is URL-encoded: All non-ASCII char‐

	     acters and the two special characters “=” and “%” are encoded as

	     “%” followed by two uppercase hexadecimal digits.	The value of

	     this key is the extended attribute value encoded in base 64.  XXX

	     Detail the base-64 format here XXX

     VENDOR.*

	     XXX document other vendor-specific extensions XXX

     Any values stored in an extended attribute override the corresponding

     values in the regular tar header.	Note that compliant readers should

     ignore the regular fields when they are overridden.  This is important,

     as existing archivers are known to store non-compliant values in the

     standard header fields in this situation.	There are no limits on length

     for any of these fields.  In particular, numeric fields can be arbitrar‐

     ily large.  All text fields are encoded in UTF8.  Compliant writers

     should store only portable 7-bit ASCII characters in the standard ustar

     header and use extended attributes whenever a text value contains non-

     ASCII characters.

     In addition to the x entry described above, the pax interchange format

     also supports a g entry.  The g entry is identical in format, but speci‐

     fies attributes that serve as defaults for all subsequent archive

     entries.  The g entry is not widely used.

     Besides the new x and g entries, the pax interchange format has a few

     other minor variations from the earlier ustar format.  The most troubling

     one is that hardlinks are permitted to have data following them.  This

     allows readers to restore any hardlink to a file without having to rewind

     the archive to find an earlier entry.  However, it creates complications

     for robust readers, as it is no longer clear whether or not they should

     ignore the size field for hardlink entries.

   GNU Tar Archives

     The GNU tar program started with a pre-POSIX format similar to that

     described earlier and has extended it using several different mechanisms:

     It added new fields to the empty space in the header (some of which was

     later used by POSIX for conflicting purposes); it allowed the header to

     be continued over multiple records; and it defined new entries that mod‐

     ify following entries (similar in principle to the x entry described

     above, but each GNU special entry is single-purpose, unlike the general-

     purpose x entry).	As a result, GNU tar archives are not POSIX compati‐

     ble, although more lenient POSIX-compliant readers can successfully

     extract most GNU tar archives.

	   struct header_gnu_tar {

		   char name[100];

		   char mode[8];

		   char uid[8];

		   char gid[8];

		   char size[12];

		   char mtime[12];

		   char checksum[8];

		   char typeflag[1];

		   char linkname[100];

		   char magic[6];

		   char version[2];

		   char uname[32];

		   char gname[32];

		   char devmajor[8];

		   char devminor[8];

		   char atime[12];

		   char ctime[12];

		   char offset[12];

		   char longnames[4];

		   char unused[1];

		   struct {

			   char offset[12];

			   char numbytes[12];

		   } sparse[4];

		   char isextended[1];

		   char realsize[12];

		   char pad[17];

	   };

     typeflag

	     GNU tar uses the following special entry types, in addition to

	     those defined by POSIX:

	     7	     GNU tar treats type "7" records identically to type "0"

		     records, except on one obscure RTOS where they are used

		     to indicate the pre-allocation of a contiguous file on

		     disk.

	     D	     This indicates a directory entry.	Unlike the POSIX-stan‐

		     dard "5" typeflag, the header is followed by data records

		     listing the names of files in this directory.  Each name

		     is preceded by an ASCII "Y" if the file is stored in this

		     archive or "N" if the file is not stored in this archive.

		     Each name is terminated with a null, and an extra null

		     marks the end of the name list.  The purpose of this

		     entry is to support incremental backups; a program

		     restoring from such an archive may wish to delete files

		     on disk that did not exist in the directory when the ar‐

		     chive was made.

		     Note that the "D" typeflag specifically violates POSIX,

		     which requires that unrecognized typeflags be restored as

		     normal files.  In this case, restoring the "D" entry as a

		     file could interfere with subsequent creation of the

		     like-named directory.

	     K	     The data for this entry is a long linkname for the fol‐

		     lowing regular entry.

	     L	     The data for this entry is a long pathname for the fol‐

		     lowing regular entry.

	     M	     This is a continuation of the last file on the previous

		     volume.  GNU multi-volume archives guarantee that each

		     volume begins with a valid entry header.  To ensure this,

		     a file may be split, with part stored at the end of one

		     volume, and part stored at the beginning of the next vol‐

		     ume.  The "M" typeflag indicates that this entry contin‐

		     ues an existing file.  Such entries can only occur as the

		     first or second entry in an archive (the latter only if

		     the first entry is a volume label).  The size field spec‐

		     ifies the size of this entry.  The offset field at bytes

		     369-380 specifies the offset where this file fragment

		     begins.  The realsize field specifies the total size of

		     the file (which must equal size plus offset).  When

		     extracting, GNU tar checks that the header file name is

		     the one it is expecting, that the header offset is in the

		     correct sequence, and that the sum of offset and size is

		     equal to realsize.

	     N	     Type "N" records are no longer generated by GNU tar.

		     They contained a list of files to be renamed or symlinked

		     after extraction; this was originally used to support

		     long names.  The contents of this record are a text

		     description of the operations to be done, in the form

		     “Rename %s to %s\n” or “Symlink %s to %s\n”; in either

		     case, both filenames are escaped using K&R C syntax.  Due

		     to security concerns, "N" records are now generally

		     ignored when reading archives.

	     S	     This is a “sparse” regular file.  Sparse files are stored

		     as a series of fragments.	The header contains a list of

		     fragment offset/length pairs.  If more than four such

		     entries are required, the header is extended as necessary

		     with “extra” header extensions (an older format that is

		     no longer used), or “sparse” extensions.

	     V	     The name field should be interpreted as a tape/volume

		     header name.  This entry should generally be ignored on

		     extraction.

     magic   The magic field holds the five characters “ustar” followed by a

	     space.  Note that POSIX ustar archives have a trailing null.

     version

	     The version field holds a space character followed by a null.

	     Note that POSIX ustar archives use two copies of the ASCII digit

	     “0”.

     atime, ctime

	     The time the file was last accessed and the time of last change

	     of file information, stored in octal as with mtime.

     longnames

	     This field is apparently no longer used.

     Sparse offset / numbytes

	     Each such structure specifies a single fragment of a sparse file.

	     The two fields store values as octal numbers.  The fragments are

	     each padded to a multiple of 512 bytes in the archive.  On

	     extraction, the list of fragments is collected from the header

	     (including any extension headers), and the data is then read and

	     written to the file at appropriate offsets.

     isextended

	     If this is set to non-zero, the header will be followed by addi‐

	     tional “sparse header” records.  Each such record contains infor‐

	     mation about as many as 21 additional sparse blocks as shown

	     here:

		   struct gnu_sparse_header {

			   struct {

				   char offset[12];

				   char numbytes[12];

			   } sparse[21];

			   char    isextended[1];

			   char    padding[7];

		   };

     realsize

	     A binary representation of the file's complete size, with a much

	     larger range than the POSIX file size.  In particular, with M

	     type files, the current entry is only a portion of the file.  In

	     that case, the POSIX size field will indicate the size of this

	     entry; the realsize field will indicate the total size of the

	     file.

   GNU tar pax archives

     GNU tar 1.14 (XXX check this XXX) and later will write pax interchange

     format archives when you specify the --posix flag.  This format follows

     the pax interchange format closely, using some SCHILY tags and introduc‐

     ing new keywords to store sparse file information.  There have been three

     iterations of the sparse file support, referred to as “0.0”, “0.1”, and

     “1.0”.

     GNU.sparse.numblocks, GNU.sparse.offset, GNU.sparse.numbytes,

	     GNU.sparse.size

	     The “0.0” format used an initial GNU.sparse.numblocks attribute

	     to indicate the number of blocks in the file, a pair of

	     GNU.sparse.offset and GNU.sparse.numbytes to indicate the offset

	     and size of each block, and a single GNU.sparse.size to indicate

	     the full size of the file.  This is not the same as the size in

	     the tar header because the latter value does not include the size

	     of any holes.  This format required that the order of attributes

	     be preserved and relied on readers accepting multiple appearances

	     of the same attribute names, which is not officially permitted by

	     the standards.

     GNU.sparse.map

	     The “0.1” format used a single attribute that stored a comma-sep‐

	     arated list of decimal numbers.  Each pair of numbers indicated

	     the offset and size, respectively, of a block of data.  This does

	     not work well if the archive is extracted by an archiver that

	     does not recognize this extension, since many pax implementations

	     simply discard unrecognized attributes.

     GNU.sparse.major, GNU.sparse.minor, GNU.sparse.name, GNU.sparse.realsize

	     The “1.0” format stores the sparse block map in one or more

	     512-byte blocks prepended to the file data in the entry body.

	     The pax attributes indicate the existence of this map (via the

	     GNU.sparse.major and GNU.sparse.minor fields) and the full size

	     of the file.  The GNU.sparse.name holds the true name of the

	     file.  To avoid confusion, the name stored in the regular tar

	     header is a modified name so that extraction errors will be

	     apparent to users.

   Solaris Tar

     XXX More Details Needed XXX

     Solaris tar (beginning with SunOS XXX 5.7 ?? XXX) supports an “extended”

     format that is fundamentally similar to pax interchange format, with the

     following differences:

     ·	     Extended attributes are stored in an entry whose type is X, not

	     x, as used by pax interchange format.  The detailed format of

	     this entry appears to be the same as detailed above for the x

	     entry.

     ·	     An additional A header is used to store an ACL for the following

	     regular entry.  The body of this entry contains a seven-digit

	     octal number followed by a zero byte, followed by the textual ACL

	     description.  The octal value is the number of ACL entries plus a

	     constant that indicates the ACL type: 01000000 for POSIX.1e ACLs

	     and 03000000 for NFSv4 ACLs.

   AIX Tar

     XXX More details needed XXX

     AIX Tar uses a ustar-formatted header with the type A for storing coded

     ACL information.  Unlike the Solaris format, AIX tar writes this header

     after the regular file body to which it applies.  The pathname in this

     header is either NFS4 or AIXC to indicate the type of ACL stored.	The

     actual ACL is stored in platform-specific binary format.

   Mac OS X Tar

     The tar distributed with Apple's Mac OS X stores most regular files as

     two separate files in the tar archive.  The two files have the same name

     except that the first one has “._” prepended to the last path element.

     This special file stores an AppleDouble-encoded binary blob with addi‐

     tional metadata about the second file, including ACL, extended

     attributes, and resources.  To recreate the original file on disk, each

     separate file can be extracted and the Mac OS X copyfile() function can

     be used to unpack the separate metadata file and apply it to th regular

     file.  Conversely, the same function provides a “pack” option to encode

     the extended metadata from a file into a separate file whose contents can

     then be put into a tar archive.

     Note that the Apple extended attributes interact badly with long file‐

     names.  Since each file is stored with the full name, a separate set of

     extensions needs to be included in the archive for each one, doubling the

     overhead required for files with long names.

   Summary of tar type codes

     The following list is a condensed summary of the type codes used in tar

     header records generated by different tar implementations.  More details

     about specific implementations can be found above:

     NUL  Early tar programs stored a zero byte for regular files.

     0	  POSIX standard type code for a regular file.

     1	  POSIX standard type code for a hard link description.

     2	  POSIX standard type code for a symbolic link description.

     3	  POSIX standard type code for a character device node.

     4	  POSIX standard type code for a block device node.

     5	  POSIX standard type code for a directory.

     6	  POSIX standard type code for a FIFO.

     7	  POSIX reserved.

     7	  GNU tar used for pre-allocated files on some systems.

     A	  Solaris tar ACL description stored prior to a regular file header.

     A	  AIX tar ACL description stored after the file body.

     D	  GNU tar directory dump.

     K	  GNU tar long linkname for the following header.

     L	  GNU tar long pathname for the following header.

     M	  GNU tar multivolume marker, indicating the file is a continuation of

	  a file from the previous volume.

     N	  GNU tar long filename support.  Deprecated.

     S	  GNU tar sparse regular file.

     V	  GNU tar tape/volume header name.

     X	  Solaris tar general-purpose extension header.

     g	  POSIX pax interchange format global extensions.

     x	  POSIX pax interchange format per-file extensions.

SEE ALSO

     ar(1), pax(1), tar(1)

STANDARDS

     The tar utility is no longer a part of POSIX or the Single Unix Standard.

     It last appeared in Version 2 of the Single UNIX Specification (“SUSv2”).

     It has been supplanted in subsequent standards by pax(1).	The ustar for‐

     mat is currently part of the specification for the pax(1) utility.  The

     pax interchange file format is new with IEEE Std 1003.1-2001 (“POSIX.1”).

HISTORY

     A tar command appeared in Seventh Edition Unix, which was released in

     January, 1979.  It replaced the tp program from Fourth Edition Unix which

     in turn replaced the tap program from First Edition Unix.	John Gilmore's

     pdtar public-domain implementation (circa 1987) was highly influential

     and formed the basis of GNU tar (circa 1988).  Joerg Shilling's star

     archiver is another open-source (CDDL) archiver (originally developed

     circa 1985) which features complete support for pax interchange format.

     This documentation was written as part of the libarchive and bsdtar

     project by Tim Kientzle <kientzle@FreeBSD.org>.

BSD			       December 27, 2016			   BSD