NAME
star - tape archive file format
DESCRIPTION
Tar Archives are layered archives. The basic structure is defined by
the POSIX.1-1988 archive format and documented in the BASIC TAR HEADER
DESCRIPTION section below. The higher level structure is defined by
the POSIX.1-2001 extended headers and documented in the EXTENDED TAR
(PAX) HEADER STRUCTURE section below. POSIX.1-2001 extended headers
are pseudo files that contain an unlimited number of extended header
keywords and associated values. The header keywords are documented in
the EXTENDED TAR (PAX) HEADER KEYWORDS section below.
BASIC TAR HEADER DESCRIPTION
Physically, a POSIX.1-1988 tar archive consists of a series of fixed
sized blocks of TBLOCK (512) characters. It contains a series of file
entries terminated by a logical end-of-archive marker, which consists
of two blocks of 512 bytes of binary zeroes. Each file entry is
represented by a header block that describes the file followed by one
or more blocks with the content of the file. The length of each file is
rounded up to a multiple of 512 bytes.
A number of TBLOCK sizes blocks are grouped together to a tape record
for physical I/O operations. Each record of n blocks is written with a
single write(2) operation. On magnetic tapes, this results in a single
tape record.
The header block is defined in star.h as follows:
/*
* POSIX.1-1988 field size values and magic.
*/
#define TBLOCK 512
#define NAMSIZ 100
#define PFXSIZ 155
#define TMODLEN 8
#define TUIDLEN 8
#define TGIDLEN 8
#define TSIZLEN 12
#define TMTMLEN 12
#define TCKSLEN 8
#define TMAGIC "ustar" /* ustar magic 6 chars + ’\0’ */
#define TMAGLEN 6 /* "ustar" including ’\0’ */
#define TVERSION "00"
#define TVERSLEN 2
#define TUNMLEN 32
#define TGNMLEN 32
#define TDEVLEN 8
/*
* POSIX.1-1988 typeflag values
*/
#define REGTYPE ’0’ /* Regular File */
#define AREGTYPE ’\0’ /* Regular File (outdated) */
#define LNKTYPE ’1’ /* Hard Link */
#define SYMTYPE ’2’ /* Symbolic Link */
#define CHRTYPE ’3’ /* Character Special */
#define BLKTYPE ’4’ /* Block Special */
#define DIRTYPE ’5’ /* Directory */
#define FIFOTYPE ’6’ /* FIFO (named pipe) */
#define CONTTYPE ’7’ /* Contiguous File */
/*
* POSIX.1-2001 typeflag extensions.
* POSIX.1-2001 calls the extended USTAR format PAX although it is
* definitely derived from and based on USTAR. The reason may be that
* POSIX.1-2001 calls the tar program outdated and lists the
* pax program as the successor.
*/
#define LF_GHDR ’g’ /* POSIX.1-2001 global extended header */
#define LF_XHDR ’x’ /* POSIX.1-2001 extended header */
See section EXTENDED TAR (PAX) HEADER KEYWORDS for more information
about the structure of a POSIX.1-2001 header.
/*
* star/gnu/Sun tar extensions:
*
* Note that the standards committee allows only capital A through
* capital Z for user-defined expansion. This means that defining
* something as, say ’8’ is a *bad* idea.
*/
#define LF_ACL ’A’ /* Solaris Access Control List */
#define LF_DUMPDIR ’D’ /* GNU dump dir */
#define LF_EXTATTR ’E’ /* Solaris Extended Attribute File */
#define LF_META ’I’ /* Inode (metadata only) no file content */
#define LF_LONGLINK ’K’ /* NEXT file has a long linkname */
#define LF_LONGNAME ’L’ /* NEXT file has a long name */
#define LF_MULTIVOL ’M’ /* Continuation file rest to be skipped */
#define LF_NAMES ’N’ /* OLD GNU for names > 100 characters */
#define LF_SPARSE ’S’ /* This is for sparse files */
#define LF_VOLHDR ’V’ /* tape/volume header Ignore on extraction */
#define LF_VU_XHDR ’X’ /* POSIX.1-2001 xtended (Sun VU version) */
/*
* Definitions for the t_mode field
*/
#define TSUID 04000 /* Set UID on execution */
#define TSGID 02000 /* Set GID on execution */
#define TSVTX 01000 /* On directories, restricted deletion flag */
#define TUREAD 00400 /* Read by owner */
#define TUWRITE 00200 /* Write by owner special */
#define TUEXEC 00100 /* Execute/search by owner */
#define TGREAD 00040 /* Read by group */
#define TGWRITE 00020 /* Write by group */
#define TGEXEC 00010 /* Execute/search by group */
#define TOREAD 00004 /* Read by other */
#define TOWRITE 00002 /* Write by other */
#define TOEXEC 00001 /* Execute/search by other */
#define TALLMODES 07777 /* The low 12 bits */
/*
* This is the ustar (Posix 1003.1) header.
*/
struct header {
char t_name[NAMSIZ]; /* 0 Filename */
char t_mode[8]; /* 100 Permissions */
char t_uid[8]; /* 108 Numerical User ID */
char t_gid[8]; /* 116 Numerical Group ID */
char t_size[12]; /* 124 Filesize */
char t_mtime[12]; /* 136 st_mtime */
char t_chksum[8]; /* 148 Checksum */
char t_typeflag; /* 156 Typ of File */
char t_linkname[NAMSIZ]; /* 157 Target of Links */
char t_magic[TMAGLEN]; /* 257 "ustar" */
char t_version[TVERSLEN]; /* 263 Version fixed to 00 */
char t_uname[TUNMLEN]; /* 265 User Name */
char t_gname[TGNMLEN]; /* 297 Group Name */
char t_devmajor[8]; /* 329 Major for devices */
char t_devminor[8]; /* 337 Minor for devices */
char t_prefix[PFXSIZ]; /* 345 Prefix for t_name */
/* 500 End */
char t_mfill[12]; /* 500 Filler up to 512 */
};
/*
* star header specific definitions
*/
#define STMAGIC "tar" /* star magic */
#define STMAGLEN 4 /* "tar" including ’\0’ */
/*
* This is the new (post Posix 1003.1-1988) xstar header
* defined in 1994.
*
* t_prefix[130] is guaranteed to be ’ ’ to prevent ustar
* compliant implementations from failing.
* t_mfill & t_xmagic need to be zero for a 100% ustar compliant
* implementation, so setting t_xmagic to
* "tar" should be avoided in the future.
*
* A different method to recognize this format is to verify that
* t_prefix[130] is equal to ’ ’ and
* t_atime[0]/t_ctime[0] is an octal number and
* t_atime[11] is equal to ’ ’ and
* t_ctime[11] is equal to ’ ’.
*
* Note that t_atime[11]/t_ctime[11] may be changed in future.
*/
struct xstar_header {
char t_name[NAMSIZ]; /* 0 Filename */
char t_mode[8]; /* 100 Permissions */
char t_uid[8]; /* 108 Numerical User ID */
char t_gid[8]; /* 116 Numerical Group ID */
char t_size[12]; /* 124 Filesize */
char t_mtime[12]; /* 136 st_mtime */
char t_chksum[8]; /* 148 Checksum */
char t_typeflag; /* 156 Typ of File */
char t_linkname[NAMSIZ]; /* 157 Target of Links */
char t_magic[TMAGLEN]; /* 257 "ustar" */
char t_version[TVERSLEN]; /* 263 Version fixed to 00 */
char t_uname[TUNMLEN]; /* 265 User Name */
char t_gname[TGNMLEN]; /* 297 Group Name */
char t_devmajor[8]; /* 329 Major for devices */
char t_devminor[8]; /* 337 Minor for devices */
char t_prefix[131]; /* 345 Prefix for t_name */
char t_atime[12]; /* 476 st_atime */
char t_ctime[12]; /* 488 st_ctime */
char t_mfill[8]; /* 500 Filler up to star magic */
char t_xmagic[4]; /* 508 "tar" */
};
struct sparse {
char t_offset[12];
char t_numbytes[12];
};
#define SPARSE_EXT_HDR 21
struct xstar_ext_header {
struct sparse t_sp[21];
char t_isextended;
};
typedef union hblock {
char dummy[TBLOCK];
long ldummy[TBLOCK/sizeof (long)]; /* force long alignment */
struct header dbuf;
struct xstar_header xstar_dbuf;
struct xstar_ext_header xstar_ext_dbuf;
} TCB;
For maximum portability, all fields that contain character strings
should be limited to use the low 7 bits of a character.
The name, linkname and prefix field contain character strings. The
strings are null terminated except when they use the full space of 100
characters for the name or linkname field or 155 characters for the
prefix field.
If the prefix does not start with a null character, then prefix and
name need to be concatenated by using the prefix, followed a slash
character followed by the name field. If a null character appears in
name or prefix before the maximum size is reached, the field in
question is terminated. This way file names up to 256 characters may
be archived. The prefix is not used together with the linkname field,
so the maximum length of a link name is 100 characters.
The fields magic, uname and gname contain null terminated character
strings.
The version field contains the string "00" without a trailing zero. It
cannot be set to different values as POSIX.1-1988 did not specify a way
to handle different version strings. The typeflag field contains a
single character.
All numeric fields contain size-1 leading zero-filled numbers using
octal digits. They are followed by one or more space or null
characters. All recent implementations only use one space or null
character at the end of a numerical field to get maximum space for the
octal number. Star always uses a space character as terminator.
Numeric fields with 8 characters may hold up to 7 octal digits
(7777777) which results is a maximum value of 2097151. Numeric fields
with 12 characters may hold up to 11 octal digits (77777777777) which
results is a maximum value of 8589934591.
Star implements a vendor specific (and thus non-POSIX) extension to put
bigger numbers into the numeric fields. This is done by using a base
256 coding. The top bit of the first character in the appropriate 8
character or 12 character field is set to flag non octal coding. If
base 256 coding is in use, then all remaining characters are used to
code the number. This results in 7 base 256 digits in 8 character
fields and in 11 base 256 digits in 12 character fields. All base 256
numbers are two’s complement numbers. A base 256 number in a 8
character field may hold 56 bits, a base 256 number in a 12 character
field may hold 88 bits. This may extended to 64 bits for 8 character
fields and to 95 bits for 12 character fields. For a negative number
the first character currently is set to a value of 255 (all 8 bits are
set). The rightmost character in a 8 or 12 character field contains
the least significant base 256 number. Recent GNU tar versions
implement the same extension.
While the POSIX standard makes obvious that the fields mode, uid, gid,
size, chksum, devmajor and devminor should be treated as unsigned
numbers, there is no such definition for the time field.
The mode field contains 12 bits holding permissions, see above for the
definitions for each of the permission bits.
The uid and gid fields contain the numerical user id of the file.
The size field contains the size of the file in characters. If the tar
header is followed by file data, then the amount of data that follows
is computed by (size + 511) / 512.
The mtime filed contains the number of seconds since Jan 1st 1970 00:00
UTC as retrived via stat(2) in st_mtime.
The chksum field contains a simple checksum over all bytes of the
header. To compute the value, all characters in the header are treated
as unsigned integers and the characters in the chksum field are treated
as if they were all spaces. When the computation starts, the checksum
value is initialized to 0.
The typeflag field specifies the type of the file that is archived. If
a specific tar implementation does not include support for a specific
typeflag value, this implementation will extract the unknown file types
as if they were plain files.
’0’ REGTYPE
A regular file. If the size field is non zero, then file data
follows the header.
’\0’ AREGTYPE
For backwards compatibility with pre POSIX.1-1988 tar
implementations, a nul character is also recognized as marker
for plain files. It is not generated by recent tar
implementations. If the size field is non zero, then file data
follows the header.
’1’ LNKTYPE
The file is a hard link to another file. The name of the file
that the file is linked to is in the linkname part of the
header. For tar archives written by pre POSIX.1-1988
implementations, the size field usually contains the size of the
file and needs to be ignored as no data may follow this header
type. For POSIX.1-1988 compliant archives, the size field needs
to be 0. For POSIX.1-2001 compliant archives, the size field
may be non zero, indicating that file data is included in the
archive.
’2’ SYMTYPE
The file is a symbolic link to another file. The name of the
file that the file is linked to is in the linkname part of the
header. The size field needs to be 0. No file data may follow
the header.
’3’ CHRTYPE
A character special file. The fields devmajor and devminor
contain information that defines the file. The meaning of the
size field is unspecified by the POSIX standard. No file data
may follow the header.
’4’ BLKTYPE
A block special file. The fields devmajor and devminor contain
information that defines the file. The meaning of the size
field is unspecified by the POSIX standard. No file data may
follow the header.
’5’ DIRTYPE
A directory or sub directory. Old (pre POSIX.1-1988) tar
implementations did use the same typeflag value as for plain
files and added a slash to the name. If the size field is non
zero then it indicates the maximum size in characters the system
may allocate for this directory. If the size field is 0, then
the system shall not limit the size of the directory. On
operating systems where the disk allocation is not done on a
directory base, the size field is ignored on extraction. No
file data may follow the header.
’6’ FIFOTYPE
A named pipe. The meaning of the size field is unspecified by
the POSIX standard. The size field must be ignored on
extraction. No file data may follow the header.
’7’ CONTTYPE
A contiguous file. This is a file that gives special
performance attributes. Operating systems that don’t support
this file type extract this file type as plain files. If the
size field is non zero, then file data follows the header.
’g’ GLOBAL POSIX.1-2001 HEADER
With POSIX.1-2001 pax archives, this type defines a global
extended header. The size is always non zero and denotes the
sum of the length fields in the extended header data. The data
that follows the header is in the pax extended header format.
The extended header records in this header type affect all
following files in the archive unless they are overwritten by
new values. See EXTENDED TAR (PAX) HEADER FORMAT section below.
’x’ EXTENDED POSIX.1-2001 HEADER
With POSIX.1-2001 pax archives, this type defines an extended
header. The size is always non zero and denotes the sum of the
length fields in the extended header data. The data that
follows the header is in the pax extended header format. The
extended header records in this header type only affect the
following file in the archive. See EXTENDED TAR (PAX) HEADER
FORMAT section below.
’A’ - ’Z’
Reserved for vendor specific implementations.
’A’ A Solaris ACL entry as used by the tar implementation from Sun.
The size is always non zero and denotes the length of the data
that follows the header. Star currently is not able to handle
this header type.
’D’ A GNU dump directory. This header type is not created by star
and handled like a directory during an extract operation, so the
content is ignored by star. The size field denotes the length
of the data that follows the header.
’E’ A Solaris Extended Attribute File. The size field denotes the
length of the data that follows the header. Star currently is
not able to handle this header type.
’I’ A inode metadata entry. This header type is used by star to
archive inode meta data only. To archive more inode meta data
than possible with a POSIX-1.1988 tar header, a header with type
’I’ is usually preceded by a ’x’ header. It is used with
incremental backups. The size field holds the length of the
file. No file data follows this header.
’K’ A long link name. Star is able to read and write this type of
header. With the xustar and exustar formats, star prefers to
store long link names using the POSIX.1-2001 method. The size
is always non zero and denotes the length of the long link name
including the trailing null byte. The link name is in the data
that follows the header.
’L’ A long file name. Star is able to read and write this type of
header. With the xustar and exustar formats, star prefers to
store long file names using the POSIX.1-2001 method. The size
is always non zero and denotes the length of the long file name
including the trailing null byte. The file name is in the data
that follows the header.
’M’ A multi volume continuation entry. It is used by star to tell
the extraction program via the size field when the next regular
archive header will follow. This allows to start extracting
multi volume archives with a volume number greater than one. It
is used by GNU tar to verify multi volume continuation volumes.
Other fields in the GNU multi volume continuation header are a
result of a GNU tar miss conception and cannot be used. If the
size field is non zero the data following the header is skipped
by star if the volume that starts with it is mounted as the
first volume. This header is ignored if the volume that starts
with it is mounted as continuation volume.
’N’ An outdated linktype used by old GNU tar versions to store long
file names. This type is unsupported by star.
’S’ A sparse file. This header type is used by star and GNU tar. A
sparse header is uses instead of a plain file header to denote a
sparse file that follows. Directly after the header, a list of
sparse hole descriptors follows followed by the compacted file
data. With star formats, the size field holds a size that
represents the sum of the sparse hole descriptors plus the size
of the compacted file data. This allows other tar
implementations to correctly skip to the next tar header. With
GNU tar, up to 4 sparse hole descriptors fit into the sparse
header. Additional hole descriptors are not needed if the file
has less than 4 holes. With GNU tar, the size field breaks
general tar header rules and is meaningless because the size of
the sparse hole descriptors does not count.
’V’ A volume header. The name field is is used to hold the volume
name. Star uses the atime field to hold the volume number in
case there is no POSIX.1-2001 extended header. This header type
is used by star and GNU tar. If the size field is non zero the
data following the header is skipped by star.
’X’ A vendor unique variant of the POSIX.1-2001 extended header
type. It has been implemented by Sun many years before the
POSIX.1-2001 standard has been approved. See also the typeflag
’x’ header type. Star is able to read and write this type of
header.
EXTENDED TAR (PAX) HEADER STRUCTURE
Block type Description
Ustar Header [typeflag=’g’] Global Extended Header
Global Extended Data
Ustar Header [typeflag=’h’] Extended Header
Extended Data
Ustar header [typeflag=’0’] File with Extended Header
Data for File #1
Ustar header [typeflag=’0’] File without Extended Header
Data for File #2
Block of binary zeroes First EOF Block
Block of binary zeroes Second EOF Block
EXTENDED TAR (PAX) HEADER FORMAT
The data block that follows a tar archive header with typeflag ’g’ or
’x’ contains one or more records in the following format:
"%d %s=%s\n", <length>, <keyword>, <value>
Each record starts with a a decimal length field. The length includes
the total size of a record including the length field itself and the
trailing new line.
The keyword may not include an equal sign. All keywords beginning with
lower case letters and digits are reserved for future use by the POSIX
standard.
If the value field is of zero length, it deletes any header field of
the same name that is in effect from the same extended header or from a
previous global header.
Null characters do not delimit any value. The value is only limited by
its implicit length.
EXTENDED TAR (PAX) HEADER KEYWORDS
POSIX.1-2001 extended pax header keywords. All numerical values are
represented as decimal strings. All texts are represented as 7-bit
ascii or UTF-8:
atime The time from st_atime in sub second granularity. Star
currently supports a nanosecond granularity.
charset
The name of the character set used to encode the data in the
following file(s). This keyword is currently ignored by star.
comment
Any number of characters that should be treated as comment.
Star ignores the comment as documented by the POSIX standard.
ctime The time from st_ctime in sub second granularity. Star
currently supports a nanosecond granularity.
gid The group ID of the group that owns the file. The argument is a
decimal number. This field is used if the group ID of a file is
greater than 2097151 (octal 7777777).
gname The group name of the following file(s) coded in UTF-8 if the
group name does not fit into 323 characters or cannot be
expressed in 7-Bit ASCII.
linkpath
The name of the linkpath coded in UTF-8 if it is longer than 100
characters or cannot be expressed in 7-Bit ASCII.
mtime The time from st_mtime in sub second granularity. Star
currently supports a nanosecond granularity.
path The name of the linkpath coded in UTF-8 if it does not fit into
100 characters + 155 characters prefix or cannot be expressed in
7-Bit ASCII.
realtime.any
The keywords prefixed by realtime. are reserved for future
standardization.
security.any
The keywords prefixed by security. are reserved for future
standardization.
size The size of the file as decimal number if the file size is
greater than 8589934591 (octal 77777777777). The size keyword
may not refer to the real file size but is related to the size
if the file in the archive. See also SCHILY.realsize for more
information.
uid The uid ID of the group that owns the file. The argument is a
decimal number. This field is used if the uid ID of a file is
greater than 2097151 (octal 7777777).
uname The user name of the following file(s) coded in UTF-8 if the
user name does not fit into 323 characters or cannot be
expressed in 7-Bit ASCII.
VENDOR.keyword
Any keyword that starts with a vendor name in capital letters is
reserved for vendor specific extensions by the standard. Star
uses a lot of these vendor specific extension. See below for
more informations.
SCHILY PAX EXTENSION KEYWORDS
Star uses own vendor specific extensions. The SCHILY vendor specific
extended pax header keywords are:
SCHILY.acl.access
The ACL for a file.
Since no official backup format for POSIX access control lists
has been defined, star uses the vendor defined attributes
SCHILY.acl.access and SCHILY.acl.default for storing the ACL and
Default ACL of a file, respectively. The access control lists
are stored in the short text form as defined in POSIX 1003.1e
draft standard 17.
To each named user ACL entry a fourth colon separated field
field containing the user identifier (UID) of the associated
user is appended. To each named group entry a fourth colon
separated field containing the group identifier (GID) of the
associated group is appended. (POSIX 1003.1e draft standard 17
allows to add fields to ACL entries.)
This is an example of the format used for SCHILY.acl.access (a
space has been inserted after the equal sign and lines are
broken [marked with ’\’ ] for readability, additional fields in
bold):
SCHILY.acl.access= user::rwx,user:lisa:r-x:502, \
group::r-x,group:toolies:rwx:102, \
mask::rwx,other::r--x
The numerical user and group identifiers are essential when
restoring a system completely from a backup, as initially the
name-to-identifier mappings may not be available, and then file
ownership restoration would not work.
As the archive format that is used for backing up access control
lists is compatible with the pax archive format, archives
created that way can be restored by star or a POSIX.1-2001
compliant pax. Note that programs other than star will ignore
the ACL information.
SCHILY.acl.default
The default ACL for a file. See SCHILY.acl.access for more
information.
This is an example of the format used for SCHILY.acl.default (a
space has been inserted after the equal sign and lines are
broken [marked with ’\’ ] for readability, additional fields in
bold):
SCHILY.acl.default= user::rwx,user:lisa:r-x:502, \
group::r-x,mask::r-x,other::r-x
SCHILY.acl.type
The ACL type used for coding access control lists.
The following ACL types are possible:
POSIX draft
ACLs as defined in POSIX 1003.1e draft standard 17.
NFSv4 ACLs as used by NFSv4, NTFS and ZFS.
Star currently only implements POSIX draft ACLs. If the
SCHILY.acl.type keyword is missing, POSIX draft ACLs are asumed.
SCHILY.ddev
The device ids for names used is the SCHILY.dir dump directory
list from st_dev of the file as decimal number. The SCHILY.ddev
keyword is followed by a space separated list of device id
numbers. Each corresponds exactly to a name in the list found in
SCHILY.dir. If a specific device id number is repeated, a comma
(,) without a following space may be use to denote that the
current device id number is identical to the previous number.
This keyword is used in dump mode. This keyword is not yet
implemented.
The value is a signed int. An implementation should be able to
handle at least 64 bit values. Note that the value is signed
because POSIX does not specify more than the type should be an
int.
SCHILY.dev
The device id from st_dev of the file as decimal number. This
keyword is used in dump mode.
The value is a signed int. An implementation should be able to
handle at least 64 bit values. Note that the value is signed
because POSIX does not specify more than the type should be an
int.
SCHILY.devmajor
The device major number of the file if it is a character or
block special file. The argument is a decimal number. This
field is used if the device major of the file is greater than
2097151 (octal 7777777).
The value is a signed int. An implementation should be able to
handle at least 64 bit values. Note that the value is signed
because POSIX does not specify more than the type should be an
int.
SCHILY.devminor
The device minor number of the file if it is a character or
block special file. The argument is a decimal number. This
field is used if the device minor of the file is greater than
2097151 (octal 7777777).
The value is a signed int. An implementation should be able to
handle at least 64 bit values. Note that the value is signed
because POSIX does not specify more than the type should be an
int.
SCHILY.dino
The inode numbers for names used is the SCHILY.dir dump
directory list from st_ino of the file as decimal number. The
SCHILY.dino keyword is followed by a space separated list of
inode numbers. Each corresponds exactly to a name in the list
found in SCHILY.dir. This keyword is used in dump mode.
The values are unsigned int. An implementation should be able
to handle at least 64 bit unsigned values.
SCHILY.dir
A list of filenames (the content) for the current directory.
The names are coded in UTF-8. Each file name is prefixed by a
single character that is used as a flag. Each file name is
limited by a null character. The null character is directly
followed by he flag character for the next file name in case the
list is not terminated by the current file name. The flag
character must not be a null character. By default, a ^A (octal
001) is used. The following flags are defined:
\000 This is the list terminator character - the second null
byte, see below.
^A The default flag that is used in case the dump dir
features have not been active.
Y A non directory file that is in the current (incremental)
dump.
N A non directory file that is not in the current
(incremental) dump.
D A directory that is in the current (incremental) dump.
d A directory that is not in the current (incremental)
dump.
The list is terminated by two successive null bytes. The first
is the null byte for the last file name. The second null byte
is at the position where a flag character would be expected, it
acts ad a list terminator. The length tag for the SCHILY.dir
data includes both null bytes.
If a dump mode has been selected that writes compact complete
directory information to the beginning of the archive, the flag
character may contain values different from ^A. Star
implementations up to star-1.5 do not include this feature. Tar
implementations that like to read archives that use the
SCHILY.dir keyword, shall not rely on values other than \000
(^@) or \001 (^A).
This keyword is used in dump mode.
SCHILY.fflags
A textual version of the BSD or Linux extended file flags. As
this tag has not yet been documented, please look into the star
source, file fflags.c for more information.
SCHILY.filetype
A textual version of the real file type of the file. The
following names are used:
unallocated An unknown file type that may be a
result of a unlink(2) operation. This
should never happen.
regular A regular file.
contiguous A contiguous file. On operating systems
or file systems that don’t support this
file type, it is handled like a regular
file.
symlink A symbolic link to any file type.
directory A directory.
character special A character special file.
block special A block special file.
fifo A named pipe.
socket A UNIX domain socket.
mpx character special A multiplexed character special file.
mpx block special A multiplexed block special file.
XENIX nsem A XENIX named semaphore.
XENIX nshd XENIX shared data.
door A Solaris door.
eventcount A UNOS event count.
whiteout A BSD whiteout directory entry.
sparse A sparse regular file.
volheader A volume header.
unknown/bad Any other unknown file type. This
should never happen.
SCHILY.ino
The inode number from st_ino of the file as decimal number.
This keyword is used in dump mode.
The value is an unsigned int. An implementation should be able
to handle at least 64 bit unsigned values.
SCHILY.nlink
The link count of the file as decimal number. This keyword is
used in dump mode.
The value is an unsigned int. An implementation should be able
to handle at least 32 bit unsigned values.
SCHILY.offset
The offset value for a multi volume continuation header. This
keyword is used with multi volume continuation headers. Multi
volume continuation headers are used to allow to start reading a
multi volume archive past the first volume.
The value is an unsigned int. An implementation should be able
to handle at least 64 bit unsigned values.
SCHILY.realsize
The real size of the file as decimal number. This keyword is
used if the real size of the file differs from the visible size
of the file in the archive. The real file size differs from the
size in the archive if the file type is sparse or if the file is
a continuation file on a multi volume archive. In case the
SCHILY.realsize keyword is needed, it must be past any size
keyword in case a size keyword is also present.
The value is an unsigned int. An implementation should be able
to handle at least 64 bit unsigned values.
SCHILY.tarfiletype
The following additional file types are used in
SCHILY.tarfiletype:
hardlink
A hard link to any file type.
dumpdir
A directory with dump entries
multivol continuation
A multi volume continuation for any file type.
meta A meta entry (inode meta data only) for any file type.
SCHILY.xattr.attr
A POSIX.1-2001 coded version of the Linux extended file
attributes. Linux extended file attributes are name/value
pairs. Every attribute name results in a SCHILY.xattr.name tag
and the value of the extended attribute is used as the value of
the POSIX.1-2001 header tag. Note that this way of coding is
not portable across platforms. A version for BSD may be created
but Solaris includes far more features with extended attribute
files than Linux does.
A future version of star will implement a similar method as the
tar program on Solaris currently uses. When this implementation
is ready, the SCHILY.xattr.name feature may be removed in favor
of a truly portable implementation that supports Solaris also.
SCHILY ’G’LOBAL PAX EXTENSION KEYWORDS
The following star vendor unique extensions may only appear in ’g’lobal
extended pax headers:
SCHILY.archtype
The textual version of the archive type used. The textual
values used for SCHILY.archtype are the same names that are used
in the star command line options to set up a specific archive
type.
In order to allow archive type recognition from this keyword,
the minimum tape block size must be 2x512 bytes (1024 bytes) and
the SCHILY.archtype keyword needs to be in the first 512 bytes
of the content of the first ’g’lobal pax header. Then the first
tape block may be scanned to recognize the archive type.
SCHILY.release
The textual version of the star version string and the platform
name where this star has been compiled. The same text appears
when calling star -version.
SCHILY.volhdr.blockoff
This keyword is used for multi volume archives. It represents
the offset within the whole archive expressed in 512 byte units.
The value is an unsigned int with a valid range between 1 and
infinity. An implementation should be able to handle at least 64
bit unsigned values.
SCHILY.volhdr.blocksize
The tape blocksize expressed in 512 byte units that was used
when writing the archive.
The value is an unsigned int with a valid range between 1 and
infinity. An implementation should be able to handle at least 31
bit unsigned values.
SCHILY.volhdr.cwd
This keyword is used in dump mode. It is only used to contain
the real backup working directory if the fs-name= option of star
is used to overwrite the SCHILY.volhdr.filesys value.
Overwriting SCHILY.volhdr.filesys is needed when backups are run
on file system snapshots rather than on the real file system.
SCHILY.volhdr.device
This keyword is used in dump mode. It represents the name of
the device that holds the file system data. For disk based file
systems, this is the device name of the mounted device.
This keyword is optional. It helps to correctly identify the
file system from which this dump has been made.
SCHILY.volhdr.dumpdate
This keyword is used in dump mode. It represents the time the
current dump did start.
SCHILY.volhdr.dumplevel
This keyword is used in dump mode. It represents the level of
the current dump. Dump levels are small numbers, the lowest
possible number is 0. Dump level 0 represents a full backup.
Dump level 1 represents a backup that contains all changes that
did occur since the last level 0 dump. Dump level 2 represents
a backup that contains all changes that did occur since the last
level 1 dump. Star does not specify a maximum allowed dump
level but you should try to keep the numbers less than 100.
The value is an unsigned int with a valid range between 0 and at
least 100.
SCHILY.volhdr.dumptype
This keyword is used in dump mode. If the dump is a complete
dump of a file system, then the argument is the text full, else
the argument is the text partial.
SCHILY.volhdr.filesys
This keyword is used in dump mode. It represents the top level
directory for the file system from which this dump has been
made. If the dump represents a dump that has an associated
level, then the this directory needs to be identical to the root
directory of this file system which is the mount point.
SCHILY.volhdr.hostname
This keyword is used in dump mode. The value is retrieved from
gethostname(3) or uname(2).
SCHILY.volhdr.label
The textual volume label. The volume label must be identical
within a set of multi volume archives.
SCHILY.volhdr.refdate
This keyword is used in dump mode if the current dump is an
incremental dump with a level > 0. It represents the time the
related dump did start.
SCHILY.volhdr.reflevel
This keyword is used in dump mode if the current dump is an
incremental dump with a level > 0. It represents the level of
the related dump. The related dump is the last dump with a
level that is lower that the level of this dump. If a dump with
the level of the current dump -1 exists, then this is the
related dump level. Otherwise, the dump level is decremented
until a valid dump level could be found in the dump database.
The value is an unsigned int with a valid range between 0 and at
least 100.
SCHILY.volhdr.tapesize
This keyword is used for multi volume archives and may be used
to verify the volume size on read back. It represents the tape
size expressed in 512 byte units. If this keyword is set in
multi volume mode, the size of the tape is not autodetected but
set from a command line option.
The value is an unsigned int with a valid range between 1 and
infinity. An implementation should be able to handle at least 64
bit unsigned values.
SCHILY.volhdr.volume
This keyword is used for multi volume archives. It represents
the volume number within a volume set. The number used for the
first volume is 1.
The value is an unsigned int with a valid range between 1 and
infinity. An implementation should be able to handle at least 31
bit unsigned values.
MULTI VOLUME ARCHIVE HANDLING
To be documented in the future.
SEE ALSO
NOTES
BUGS
AUTHOR