NAME¶

star - unique standard tape archiver

SYNOPSIS¶

star  command [options] [-find] file1 ... filen [find_expr]
ustar command [options] [-find] file1 ... filen [find_expr]
star  command list=name [options] -find [find_expr]
tar   command [options]         file1 ... filen
star  -copy   [options] [-find] file1 ... [f_expr] directory
star  -copy   [options] -C from_directory . to_directory
star  cli=name   ...

DESCRIPTION¶

Star is a very fast tar(1) like tape archiver with improved functionality. It supports unlimited path name lengths (up to 8 GB) in all cases that use suitable archive types.

Star archives and extracts multiple files to and from a single file called a tarfile. A tarfile is usually a magnetic tape, but it can be any file. In all cases, appearance of a directory name refers to the files and (recursively) subdirectories of that directory.

Star's actions are controlled by the mandatory command flags from the list below. The way star acts may be modified by additional options.

Note that unpacking tar archives may be a security risk because star may overwrite existing files. See SECURITY NOTES for more information.

If the first argument is in the form cli=name, the command line interface is selected to match name. See section CLI SELECTION below.

FEATURES¶

Star includes the first free implementation of POSIX.1-2001 extended tar headers. The POSIX.1-2001 extended tar headers define a new standard way for going beyond the limitations of the historic tar format. They allow (among others) to archive all UNIX time stamps in sub-second resolution, files of arbitrary size and filenames without length limitation using UNICODE UTF-8 coding for best exchange compatibility.

Star by default uses a fifo to optimize data flow from/to tape. This results in a normally streaming tape during the whole backup. See -fifo and fs= option to get information on how to find the best fifo size.

Star includes a pattern matcher to control the list of files to be processed. This gives a convenient interface for archiving and restoring complex lists of files. In conjunction with the -w flag it is easy to merge a tar archive into an existing file tree. See also -U option. In create mode use the pat= option to specify either select or exclude patterns (depending on the -V flag). In extract or list mode all file type arguments are interpreted as select patterns while the patterns specified with the pat= option may be used as select or exclude patterns (depending on the -V flag). Have a look at the description of the -C option to learn how to fetch files from a list of directories (in create mode) or to distribute files to a list of directories (in extract mode). A substitute option allows ed(1) like pattern substitution in file names.

Star includes support for incremental backup and restore similar to the BSD commands dump(1) and restore(1) that are known as ufsdump(1) and ufsrestore(1) on Solaris.

Star includes an enhanced function that is similar to the find(1) command (see sfind(1)). This function is implemented in libfind. It allows one to use find expressions, even in extract or list mode, directly on the content on an archive. The extensions to find(1) allow one to modify the file metadata.

Star includes a sophisticated diff command that is able to compare file content and meta data. Several diff options allow user tailorable functionality. Star won't show you differences you are not interested in. Check the diffopts= option for more details.

Star has no limitation on filename length. Pathnames and linknames up to PATH_MAX (typically 1024 bytes) may be archived by most tar implementrations. Star allows one to archive path names up to 8 GB on modern platforms.

Star deals with all 3 times, available for files on UNIX systems if the archive format is either chosen from the star specific formats or is a format that uses POSIX.1-2001 extended headers. This is either done in second resolution by using a star specific POSIX.1-1988 compatible extension or in sub second resolution by using POSIX.1-2001 extended headers. Star is able to store and restore all 3 times (mtime, atime and even ctime). On Solaris 2.x systems - if run as root -, star is able to do backups without changing any of the 3 the times.

If used with the H=ustar option, or if called as ustar or tar while the H=headertype option is not used, star is 100% POSIX compliant.

Star's default format (if called as star) is xstar and is as posix compliant as possible. Enhancements to the standard that prevent correct extraction of single files when using a different tar implementation that is only POSIX.1-1988 compliant may occur, but they only affect single files with a pathname that is longer than 100+130 chars or when archiving sparse files with the -sparse option in effect. All other files will extract correctly. See the description for the H=headertype option below for more information on archive formats and possible archive interchange problems.

Star makes it easy to repair corrupted filesystems. After a fsck -y has been run on the filesystem, star is able to restore only the missing files automatically. Use then star -diff to check for differences (see EXAMPLES for more information).

Star automatically recognizes the type of the archive. Star therefore is able to handle features and properties of different archive types in their native mode, if it knows about the peculiarities of the archive type. See the H=headertype option for more details. To be able to do this, star adds hidden fingerprints to the archive header that allows one to recognise all star specific archive formats. The GNU tar format is recognised by the way it deviates from the standard.

Star automatically recognizes and handles byte swapped archives. There is no option to manually control byte swapping.

Star is able to archive and restore Access Control Lists for files using POSIX.1-2001 extended headers.

CLI SELECTION¶

If the first argument is in the form cli=name, the command line interface is selected to match one of the supported CLI variants. The following interfaces are supported:

star

The star interface selects the command line interface described in this manual page.

suntar

The suntar interface selects the command line interface of the classical UNIX tar command as described in suntar(1).

tar

The classical tar interface selects the command line interface of the classical UNIX tar command. This is currently an alias to suntar and implements extensions introduced by the tar command found on Solaris.

gnutar

The gnutar interface selects the command line interface of the GNU tar command as described in gnutar(1). Star however does not implement the deviations from the standard behavior, that are caused by the GNU option parser that is used by the original gtar(1) command.

pax

The pax interface selects the command line interface of the POSIX pax command as described in spax(1).

cpio

The cpio interface selects the command line interface of the classical UNIX cpio command as described in scpio(1).

COMMAND¶

In native mode, star is compatible to the command line syntax of a typical POSIX command and for this reason expects commands and options to start with a single dash (-). In this case, commands and options may be specified separately, all boolean or increment type options may be specified either separately or combined.

For compatibility with GNU programs, long options may alternatively start with a double dash.

In compatibility mode to POSIX tar, star expects commands and options to appear as one single string that does not start with a dash. In POSIX tar compatibility mode, additional non POSIX options may be specified but must appear after the POSIX options and their args and need to start with a dash.

-c

Create a new tarfile and write named files into it. Writing starts at the beginning of tarfile. See -v option for information on how to increase verbosity while the archive is written.

The Option -c may be used together with -diff and -t. In this case, the whole command line has to be similar to the command line for the -copy mode.

-copy

Copy named files to the target directory which is the last file type argument. The target directory must exist. The shorthand -cx instead of -copy is not allowed because this could be a result of a typo.

If the option -diff has been specified in addition, star performs a one pass directory tree compare instead of copying files. The shorthand -c -diff instead of -copy -diff is also allowed.

On operating systems with slow file I/O (such as Linux with any filesystem or platforms with Copy on Write filesystems like ZFS), it may help to use -no-fsync in addition (see also ENVIRONMENT and FILES), but then star is unable to detect all error conditions; so use with care.

If the option -t has been specified in addition, the last file type argument is not a target directory and star is performing a one pass listing instead of copying files. This makes sense as the listing from star may be better readable than the output from ls -lR. The shorthand -c -t or -ct instead of -copy -t is also allowed.

The job is by default done in the best archive mode. This implies that it defaults to H=exustar -dump. When in -copy mode, star forks into two processes and data exchange is done via the shared memory from the FIFO. This gives the best possible performance. Without FIFO, the -copy mode will not work.

The list= option, patterns and substitutions apply only to the create side of the copy command.

-diff

Compare the content and the attributes of the files from the archive in tarfile to the filesystem. This may also be used to compare two file trees in the filesystem. If you use a set of diffopts that fits your needs, it will give - in many cases - a more readable output than diff -r. If you use star's dump extensions for the tar archive, the -diff option allows one to find even if the directory in the file tree contains more files than the archive. This way, it is possible to compare all properties of two file trees in one run. See diffopts for more details. Adding one or more -v options increases the verbosity. With -vv and above, the directory content is compared also if star is reading a tar archive that has been created in -dump mode.

-n

No extraction. Show what star would do, in case the -x command had been specified.

-r

Replace files in a tarfile. The named files are written to the end of tarfile. This implies that later, the appropriate files will be found more than once on the tarfile.

-t

Table of contents. List the contents of the tarfile. If the -v flag is used, the listing is similar to the format of ls -l output. With this option, the flags -a, -atime and -ctime have a different meaning if the archive is in star, xstar, xustar, exustar, or pax/epax format. The option -a or -atime lists the access time instead of the modification time, the option -ctime lists the file creation time instead of the modification time. The option -tpath may be used in addition to modify the output so it may be used in shell scripts.

-u

Update a tarfile. The named files are written to the end of tarfile if they are not already there or if the files are newer than the files of the same name found in the archive. The -r and -u command only work if the tar archives is a regular file or if the tar archive is an unblocked tape that may backspace.

-x

Extract the named files from the tarfile. If no filename argument or pattern is specified, the entire content of the tarfile is restored. If the -U flag is not used, star extracts no file which is older than the corresponding file on disk.

On operating systems with slow file I/O (such as Linux with any filesystem or platforms with Copy on Write filesystems like ZFS), it may help to use -no-fsync in addition (see also ENVIRONMENT and FILES), but then star is unable to detect all error conditions; so use with care.

Except for the shorthands documented above, exactly one of the commands above must be specified.

If one or more patterns or substitution commands have been specified, they apply to any of the command listed above. In copy mode, all patterns and substitute commands apply to the create side.

OPTIONS¶

-help

Print a summary of the most important options for star(1).

-xhelp

Print a summary of the less important options for star(1).

-/

Don't strip leading slashes from file names when extracting an archive. Tar archives containing absolute pathnames are usually a bad idea. With other tar implementations, they may possibly never be extracted without clobbering existing files. Star for that reason, by default strips leading slashes from filenames when in extract mode. As it may be impossible to create an archive where leading slashes have been stripped while retaining correct path names, star does not strip leading slashes in create mode.

See SECURITY NOTES for more information.

-..

Don't skip files that contain /../ in the name. Tar archives containing names with /../ could be used to compromise the system. If they are unpacked together with a lot of other files, this would in most cases not even be noticed. For this reason, star by default does not extract files that contain /../ in the name if star is not in interactive mode (see -w option).

See SECURITY NOTES for more information.

-7z

Run the input or output through a p7zip pipe. See section COMPRESSION for details.

-0

-1

-2

-3

-4

-5

-6

-7

Select an archive entry from /etc/default/star. The format for the archive entries is the same as the format in /etc/default/tar in Solaris.

-acl

Handle Access Control List (ACL) information in create and extract mode. If -acl has been specified, star is in create mode and the header type is exustar, star will add ACL information to the archive using POSIX.1-2001 extended headers. If -acl has been specified and star is in extract mode, star will try to restore ACL information. If there is no ACL information for one or all files in the archive, star will clear the ACL information for the specific file. Note that if -acl has not been specified, star will not handle ACL information at all and files may inherit ACL information from the parent directories. If the -acl option has been specified, star assumes that the -p option has been specified too.

Star currently supports ACLs from the withdrawn POSIX.1e draft and NFSv4 ACLs. To check which ACL flavors are supported on the current platform, call star -version. Whether ACLs from the withdrawn POSIX.1e draft can be converted into NFSv4 ACLs depends on the local ACL support library.

artype=headertype

Generate a tape archive in headertype format. If this option is used in extract/list mode this forces star to interpret the headers to be of type headertype. As star even in case of a user selected extract archive format does format checking, it may be that you will not be able to unpack a specific archive with all possible forced archive formats. Selecting the old tar format for extraction will always work though. Valid parameter for headertype are:

-ask_remove

obsoleted by -ask-remove

-ask-remove

Ask to remove non writable files on extraction. By default, star will not overwrite files that are read only. If this option is in effect, star will ask whether it should remove these files to allow the extraction of a file in the following way:

-atime, -a

Reset access time of files after storing them to tarfile. On Solaris 2.x, (if invoked by root) star uses the _FIOSATIME ioctl to do this. This enables star not to trash the ctime while resetting the atime of the files. If the -atime option is used in conjunction with the list command, star lists access time instead of modification time. (This works only in conjunction with the star, xstar, xustar, exustar, and with the pax/epax format.) Another option to retain the access time for the the files that are going to be archives is to readonly mount a UFS snapshot and to archive files from the mount point of the UFS snapshot.

-B

Force star to perform multiple reads (if necessary) to fill a block. This option exists so that star can work across the Ethernet, since pipes and sockets return partial blocks even when more data is coming. If star uses stdin as archive file, star behaves as if it has been called with the -B option. For this reason, the option -B in practice is rarely needed.

b=#

Set the block size for tape operations. See option blocks=#.

-block-number

Print the archive block number (archive offset / 512) at the beginning of each line when in verbose mode. This allows one to write backup scripts that archive the offsets for files and that use

mt fsr blockno

to skip to the tape block number of interest in a fast way if a single file needs to be restored.

Since the numbers printed by the -block-number option are based on a block size of 512 bytes and the tape block size is usually larger, the tape block number for the mt fsr command needs to be computed to honor the tape blocking factor.

blocks=#, b=#

Set the blocking factor of the tarfile to # times 512 bytes (unless a different multiplication factor has been specified - see bs= option for possible multiplication factors). Changing the blocking factor only makes sense when the archive is located on a real tape device or when the archive is accessed via the remote tape protocol (see f= option below). The default is to use a blocking factor of 20 i.e. 10 kBytes. Increasing the blocksize will speed up the backup. For portability with very old tar implementations (pre BSD 4.2 or pre AT&T SVR4), blocksize should not be more than 10 kBytes. For POSIX.1-1988 compatibility, blocksize should be no more than 10 kBytes. For POSIX.1-2001 compatibility, blocksize should be no more than 32 kBytes. Most systems also have a hardware limitation for the blocksize, 32 kBytes and 63 kBytes are common limits on many systems. The upper limit in any case is the size of the buffer RAM in the tape drive. Make a test if you want to make sure that the target system will handle the intended blocksize. If you use star for data exchange via tape, it is a good idea to use a blocksize of 10 kBytes unless you are sure that the reading system will handle a larger blocksize. If you use star for backup purposes with recent hardware (e.g. DLT tape drives), a blocksize of 256 kBytes results in sufficient speed and seems to be a good choice. Star allows block sizes up to 2 GByte if the system does not impose a smaller limit. If you want to determine the blocking factor when reading an unknown tar archive on tape, specify a blocking factor that is higher than the supposed blocking factor of the tape. Star then will determine the blocking factor by reading the first record of the tape and print a message:

bs=#

Set output block size to #. You may use the same method as in dd(1) and sdd(1). The number representing the size is taken in bytes unless otherwise specified. If a number is followed directly by the letter `.', `w', `b', `k', `m', `g', `t', or `p', the size is multiplied by 1, 2, 512, 1024, 1024*1024, 1024*1024*1024, 1024*1024*1024*1024 or 1024*1024*1024*1024*1024. If the size consists of numbers separated by `x' or `*', multiplication of the two numbers is performed. Thus bs=7x8k will specify a blocksize of 56 kBytes. Blocksize must be a multiple of 512 bytes. See also the description of the blocks= option for more details on blocksizes. The option bs= is preferred by people who like to use an option that behaves similar to the interface used by dd(1) and sdd(1).

-bsdchdir

Switch the behavior of the C= option to BSD style. The default behavior of star is to stay in a working directory until a new C= is seen. With BSD tar, the C= option is only related to the next file type argument.

-bz

Run the input or output through a bzip2 pipe. This option is an alias for -j. See section COMPRESSION for details.

C=dir

-C dir

Perform a chdir(2) operation to dir before storing or extracting the next files. In all cases, star will perform the chdir(2) operation relative to the current working directory of the shell.

compress-program=name

Set a named compress program. See section COMPRESSION for details.

-copydlinks

Try to recursively copy the content of linked directories instead of creating the link. This is an experimental feature that may help to unpack archives on DOS.

-copyhardlinks

This option allows one to copy hardlinked targets rather than creating the link. It helps to extract tar files on systems that do not implement hardlinks (e.g. BeOS).

-copylinks

This option allows one to copy both, hard- and symlinked targets rather than creating a link. It helps to extract tar files on systems that do not implement links (e.g. OS/2). To extract and copy all symlinks correctly, you may need to call star twice as star cannot copy files that appear in the archive later than a symlink pointing to them.

-copysymlinks

This option allows one to copy symlinked targets rather than creating a symbolic link. It helps to extract tar files on systems that do not implement links (e.g. OS/2). To extract and copy all symlinks correctly, you may need to call star twice as star cannot copy files that appear in the archive later than a symlink pointing to them.

-cpio-statistics

Instead of the star flavor of the statistics, print statistics in cpio flavor.

-ctime

If used with the list command, this lists ctime rather than mtime if the archive format is star, xstar, xustar, exustar, or pax/epax.

If star is run as root and if -ctime is used with the extract command and the same archive formats, this causes star to try to restore even the ctime of a file by generating time storms. You should not do this when in multi user mode because this may confuse programs like cron and the news system. Although star tries to eliminate the accumulative effects of the time storm, there is a tendency for the system clock to slow down a bit. The clock typically lags about one millisecond per extracted file. Use with care and check the system clock after using this feature.

If used with the create command this changes the behavior of the newer= option. Star, in this case compares the ctime of all files to the mtime of the stamp file rather then comparing the mtimes of both files.

-cumulative

A shorthand for -dump-cumulative. See -dump-cumulative for more information.

-D

Do not descend directories when in create mode. Normally, star descends the whole tree if it encounters a directory in in its file parameters. The option -D is in effect by default if the list=file option is used. If you like star to descend directories found in the list file, use the -dodesc option (see below).

-d

Do not store/create directories. Old versions of tar such as published with the seventh edition of UNIX are not able to deal with directories in tar archives. If a tar archive is generated without directories this avoids problems with tar implementations found on SYSVr3 and earlier. If used during extract, no intermediate missing directories are created.

-data-change-warn

If the size of a file changes while the file is being archived, treat this condition as a warning only that does not cause a non zero exit code. A warning message is still written if the condition is not otherwise ignored by another rule from an errctl= option. The -data-change-warn option works as if the last error control option was

errctl="WARN|GROW|SHRINK *"

The -e option or an ABORT entry in a condition set up by errctl= has a higher precedence than the -data-change-warn option. This option is ignored in extract or list mode.

-debug

Print debug messages. Among other things, this gives debug messages for header type recognition, tar type properties, EOF recognition, opening of remote archives and fifo internals.

diffopts=optlst

Comma separated list of diffopts. Valid members in optlst are:

dir-group=group

If star extracts archives as root, this option allows one to control the group id of intermediate directories created by star.

dir-owner=user

If star extracts archives as root, this option allows one to control the owner of intermediate directories created by

-dirmode

If in create mode (i.e. when storing files to archive), star stores directories past the corresponding files. This guarantees that even old tar implementations without a directory cache will be able to restore the correct times of directories. The option -dirmode should only be used if the archive needs to be extracted by an old tar implementation. If star is used to extract an archive that has been created with -dirmode the directories will not get an old time stamp unless the option -U is used while extracting the archive.

-do-fsync

Tell star to call fsync(2) for every file when in extract mode. This enables star to check whether a file could be successfully extracted. See -no-fsync for more information.

-dodesc

Force star to descend directories found in a list=file. See also the -D option above. The -dodesc option only works in create mode.

-dump

Allows creating archives with the same number of attributes as an archive that has been created with the level= option but without the restrictions that apply to a true dump.

The resultant archive may be seen as a level-less dump which includes similar attributes as a level 0 dump but may span more than a single file system and does not need to use a -C option. It has been originally introduced to make it easier to implement a star version that supports true incremental dumps, but it is kept as it gives additional benefits. Star currently sets the archive type to exustar and, in addition archives more inode meta data inside POSIX.1-2001 extended headers. See also level= option and the section INCREMENTAL BACKUPS for more information on true incremental dumps.

-dump+

Works similar to -dump but creates more global archive header meta data, e.g. the SCHILY.volhdr.hostname tag.

This helps to understand where a tar archive has been created.

-dump-cumulative

instructs star to perform incremental dumps relatively to the last incremental dump of the same level. Incremental dumps with a level higher than 0 are normally done relatively to the content of a previous dump with lower level. If incremental dumps and restores are going to be used to synchronize filesystem content, every successive incremental dump will increase in size if -dump-cumulative is not used. See section SYNCHRONIZING FILESYSTEMS for more information.

dumpdate=name

Tells star to use the mtime of the time stamp file name instead of using the start time of star. This is needed when star is run on file system snapshots. If star would use the the it's own start time with snapshots, all files that have been modified between the setup of the snapshot and the start of star would be missing on the backup.

A solution is to create the time stamp file, then to create the snapshot and later use the option dumpdate=name.

-dumpmeta

changes the behavior of star in incremental dump mode. If -dumpmeta is used and only the inode change time (st_ctime) of a file has been updated since the last incremental dump, star will archive only the meta data of the file (e.g. uid, permissions, ...) but not the file content. Using -dumpmeta will result in smaller incremental dumps, but files that have been created between two incrementals and set to an old date in st_mtime (e.g. as a result from a tar extract) will not be archived with full content. Using -dumpmeta thus may result in incomplete incremental dumps, use with extreme care.

-e

Exit immediately with exit status -3 (253) if any unexpected error occurs. The -e option works as if the last error control option was

errctl="ABORT|ALL|DIFF *"

This allows one to use the errctl= option together with the -e option and thus to ignore some error conditions while aborting on all other conditions.

errctl= name

errctl= error control spec

Add the content from file name to the error control definitions or add error control spec to the error control definitions. More than one error control file and more than one error control spec as well as a mixture of both forms is possible.

The reason for using error control is to make star quiet about error conditions that are known to be irrelevant on the quality of the archive or restore run or to tell star to abort on certain error conditions instead of trying to continue with the archive.

A typical reason to use error control is to suppress warnings about growing log files while doing a backup on a live file system. Another typical reason to use error control is to tell star to abort if e.g. a file could not be archived instead of continuing to archive other files from a list.

The error control file contains a set of lines, each starting with a list of error conditions to be ignored followed by white space followed by a file name pattern (see match(1) or patmatch(3) for more information). The error control spec uses the same syntax as a single line from the error control file. If the file name pattern needs to start with white space, use a backslash to escape the start of the file name. It is not possible to have new line characters in the file name pattern. Whenever an error situation is encountered, star checks the lines in the error control file starting from the top. If the current error condition is listed on a line in the error control file, then star checks whether the pattern on the rest of the line matches the current file name. If this is the case, star uses the current error control specification to control the current error condition.

The list of error conditions to be handled may use one or more (in this case separated by a '|' character) identifiers from the list below:

If a specific error condition is ignored, then the error condition is not only handled in a silent way but also excluded from the error statistics that are printed at the end of the star run.

Be very careful when using error control as you may ignore any error condition. If you ignore the wrong error conditions, you may not be able to see real problems anymore.

-exclude-from name

Exclude from named file, this is an alias for the -X option. See -X option for more information.

-F,-FF ...

Fast and simple exclude option for create mode. With one -F argument, star ignores all directories called SCCS and RCS. With two -F arguments, star in addition ignores all files called core errs a.out all files ending with .o. OBJ/. With three -F arguments, star ignores all sub trees starting from a directory that includes a file .mirror or .exclude and all object files and files called core errs a.out all files ending with .o. With four -F arguments, star ignores all sub trees starting from a directory that includes a file .mirror or .exclude the latter files are excluded too as well as and all object files and files called core errs a.out all files ending with .o. With five -F arguments, star in addition again excludes all directories called SCCS and RCS.

f=tarfilename

Use tarfilename as the name for the tar archive. See option file=tarfilename.

-fifo

Use a fifo to optimize data flow from/to tarfile. This option is in effect by default (it may be changed at compile time). The default fifo size is 8 MBytes on all platforms except Linux versions that do not support mmap() (4 MB because kernels before 2.4 did not handle big shared memory areas) and Sun/mc68000 (1 MB). This will star make even work on a tiny machine like a Sun 3/50. The fifo size may be modified with the fs= option. A rule of thumb for the fifo size is to use more than the buffer size of the tape drive and less then half of the real memory of the machine. A good choice would be to use a fifo size between 8 and 256 MB. This may increase backup speed up to 5% compared to the speed achieved with the default fifo size. Note that with a DLT drive from y2000 that gives 12MB/s transfer rate, a fifo of 256 MB size will keep the tape at least streaming in units of 20 seconds.

Future LTO tape drives are expected to implement transfer rates of aprox. 3GB/s and need a much larger fifo size to keep the tape streaming.

All options that start with the -f sequence are sensitive to typo problems, see BUGS section for more information.

-fifostats

Print fifo statistics at the end of a star run when the fifo has been in effect. All options that start with the -f sequence are sensitive to typo problems, see BUGS section for more information.

file=tarfilename, f=tarfilename

Use tarfilename as the name for the tar archive. Currently up to 100 file= options are possible. Specifying more then one file= option make sense in multi volume mode. In this case star will use the next name in the list every time a media change is needed. To make star behave consistent with the single file case, star loops over the list of known archive files. Note that if star is installed suid root and the first tarfile is a remote archive, only the connection to this archive will be created with root privileges. After this connection has been established as root, star switches back to the id of the caller. If any of the other archives in the list is located on a different host, star will not be able to open this archive later on, unless run by root.

Star normally uses stdin/stdout for the tar archive because the most common way to use star is in conjunction with pipes. If star is installed suid root or if it has been called by root, tarfilename may be in remote syntax: user@host:filename as in rcp(1) even if invoked by non root users. See SUID NOTES for more information.

To make a file local although it includes a colon (:), the filename must start with: '/', './' or '../'

Note that if star talks to an old rmt remote tape server that does not support symbolic open modes, it does not open a remote tape with the O_CREAT open flag because this would be extremely dangerous. If the rmt server on the other side is the rmt server that comes with star or the GNU rmt server, star may use the symbolic mode for the open flags. Only the symbolic open modes allow sending all possible open modes in a portable way to remote tape servers.

It is recommended to use the rmt server that comes with star. It is the only rmt server that gives platform independent compatibility with BSD, Sun and GNU rmt clients and it includes security features that may be set up in /etc/default/rmt. All options that start with the -f sequence are sensitive to typo problems, see BUGS section for more information.

See -rsh option on how to set up a different protocol for the connection to the remote tape server.

See ENVIRONMENT section for information on how to use ssh(1) to create a remote tape server connection.

Note that if file=- has been specified, it is no longer possible to use the -find -exec primary.

-find

This option acts a separator. If it is used, all star options must be to the left of the -find option. To the right of the -find option, star accepts the find command line syntax only.

The find expression acts as a filter between the source of file names and the consumer, which may either be the archiving engine or list/extract engine. If the find expression evaluated as TRUE, then the related file is selected for processing, otherwise it is omited.

In order to make the evaluation of the find expression more convenient, star implements additional find primaries that have side effects on the file meta data. Star implements the following additional find primaries:

-force_hole

obsoleted by -force-hole

-force-hole

Try to extract all files with holes. This even works with files that are created without the -sparse option. Star, in this case examines the content of the files in the archive and replaces writes to parts containing binary zeroes with seeks.

If used together with the -sparse option in create mode, star assumes all files to be sparse and archives files with blocks of nulls as sparse files.

This option should be used with extreme care because you sometimes get in trouble when files get unattended holes. All options that start with the -f sequence are sensitive to typo problems, see BUGS section for more information.

-force_remove

obsoleted by -force-remove

-force-remove

Force to remove non writable files on extraction. By default, star will not overwrite files that are read only. If this option is in effect, star will silently remove these files to allow the extraction of a file. All options that start with the -f sequence are sensitive to typo problems, see BUGS section for more information.

-force-restore

Force an incremental restore even if there is a dump level mismatch or a reference date mismatch. See -wtardumps, level= and sections INCREMENTAL BACKUPS and INCREMENTAL RESTORES for more information.

-freeze

Run the input or output through a freeze pipe. See section COMPRESSION for details.

fs=#

Set fifo size to #. See bs= for the possible syntax.

The default size of the fifo is 1 Mbyte on Sun mc68000 systems, 4 Mbytes on non mmap() aware Linux systems and 8 Mbytes on all other systems. See -fifo option for hints on using the right fifo size.

fs-name=mount_point

Use mount_point when recording information in /etc/tardumps and when comparing against information in /etc/tardumps for incremental backups. This makes sense when backups are made using file system snapshots and allows /etc/tardumps and the archive to contain the real name of the file system instead of the temporary mount point that is used for the snapshot device.

H=headertype

See artype=headertype option. Note that POSIX.1-2001 defines an option -H that follows symbolic links that have been encountered on the command line. For this reason, the old star option H=headertype option may go away in the future even though this option has been in use by cpio since 1989.

-h, -L

Follow symbolic links as if they were files. Normally star will not follow symbolic links but stores their values in tarfile. See also the -L option.

-hardlinks

In extract mode, this option tells star to try to create a hardlink whenever a symlink is encountered in the archive. In create mode, this option tells star to try to archive a hardlink whenever a symlink is encountered in the file system.

-hpdev

Allow 24 bits for the minor device number using 8 octal digits. Note that although it allows one to create tar archives that can be read with HP-UX tar, this creates tar archives which violate POSIX.1-1988. This option is only needed if you like to use a POSIX.1-1988 based archive format that does not include extensions. If you use the xstar format, star will use a base 256 extension that allows bigger major/minor numbers by default, if you use the xustar or the exustar format there is no limitation at all as these formats use POSIX.1-2001 extended headers to archive the major/minor numbers by default.

-i

Ignore checksum errors on tar headers. If this option is specified, star will not exit if a header with a bad checksum is found but search for the next valid header.

-install

Carefully replace existing files when extracting files. This is done similar to install(1) by first extracting the files into a temporary name and renaming the file to the final name after the extraction of that file was successful.

As star by default does not remove non-empty directories, an install that needs to remove existing non-empty directories may also need the options -force-remove and -remove-recursive.

iskip=#

Set the initial skip size to #. See bs= for the possible syntax.

The skip size is the number of bytes to ignore from the first tape record. This option is typically used if a tar archive on a tape is not read from the beginning and the tape has been forwarded before the tape is read. iskip= then specifies the offset of the first archive header within the current tape record. It does not work on compressed archives.

-j

Run the input or output through a bzip2 pipe. This option is an alias for -bz. See section COMPRESSION for details.

-keep-nonempty-dirs

Do not complain about trying to remove nonempty directories in case that -remove-recursive has not been specified.

-keep_old_files

obsoleted by -keep-old-files

-keep-old-files, -k

Keep existing files rather than restoring them from tarfile. This saves files from being clobbered even if tarfile contains a more recent version of the corresponding file.

See SECURITY NOTES for more information.

-L, -h

Follow symbolic links as if they were files. Normally star will not follow symbolic links but stores their values in tarfile. See also the -h option.

-l

Do not print a warning message if not all links to hard linked files could be dumped. This option is evaluated in the opposite way to historic tar(1) implementations and to POSIX.1. POSIX.1 requests that by default no warning messages will be printed and -l will enable warning messages when not all links could be archived.

level=dumplevel

Set level for incremental dumps. This option is used to switch star into true incremental dump mode. The dumplevel may be in the range between 0..99.

In true incremental dump mode, a -C option which is followed by the name a mount point and a dot ('.') as starting directory name is required. Only a single file system may be handled at a time. If the directory following the -C option is not referring to a root directory of a file system, the dump is called a partial dump. If the directory following the -C option is referring to a root directory of a file system and no other restrictions apply that exclude certain files from the dump, the dump is called a full dump.

By default, the tardumps database is not written. See also the tardumps=name and -wtardumps options and the section INCREMENTAL BACKUPS for more information.

-link-data

In create mode, include the data for files even if these files are hard links. This feature in create mode is currently only available for the exustar archive format and only in case -sparse has not been specified.

In extract mode, allow star to deal with data in hard linked files even if the standard would not allow this for the used archive format.

-link-dirs

When in create mode, try to find hard linked directories. Using -link-dirs will force star to keep track of all directories that will go into the archive and thus causes a lot more memory to be allocated than in the default case.

If you like to extract a cpio archive that contains hard linked directories, you also need to specify -link-dirs in extract or diff mode. This is needed because many cpio implementations create buggy archives with respect to hard links. If star would look for hard linked directories in all cases, it would detect many pseudo hard links to directories. Use -link-dirs with care if you extract cpio archives.

Note that not all filesystem allow creating hard links to directories. Also note that even though a non-root user is able detect and archive hard linked directories, all known operating systems require the extraction to be done as root in order to be able to create or remove hard links to directories. For this reason its only recommended to use this option when doing accurate backups and when hard links to directories are expected.

When the option -link-dirs is not used and hard links to directories are present, the appendant sub-tree will appear more than once on the archive and star will print Linkcount below zero warnings for non directory hard links inside the sub-tree.

list=filename

Read filenames for store/create/list/diff command from filename. The file filename must contain a list of path names, each on a separate line. This option implies the -D option. To force star to descend directories, use the -dodesc option in this case. See also the -X option.

If used together with -find, no path list is accepted after the option -find.

See also the option pkglist= for a way to specify filename, permission, owner and group.

Note that if list=- has been specified, it is no longer possible to use the -find -exec primary.

-lowmem

Try to run with reduced memory requirements. This causes star to default to 1 MB of FIFO memory. Instead of allocating memory to hold the directory content and reading the directory at once, star reads the directory name by name. This may cause star to close the directory if it runs out of file descriptors because of deeply nested directories. If a directory then does not support telldir(3)/seekdir(3), star will fail.

-lzip

Run the input or output through a lzip pipe. See section COMPRESSION for details.

-lzma

Run the input or output through a lzma pipe. See section COMPRESSION for details.

-lzo

Run the input or output through a lzop pipe. See section COMPRESSION for details.

-M, -xdev

Do not descend mount points. This is useful when doing backups of complete file systems. See NOTES for more information.

When using -find, this may not always work as expected, e.g. when the /proc filesystem is involved. Use -xdev past -find for this reason.

-m

Do not restore access and modification time. (Access time is only available if star is reading star, xstar, xustar, exustar, or pax/epax archives). If star extracts other archive types, the -m flag only refers to the modification time.

-match-tree

If in create mode a pattern does not match a directory, and -match-tree has been specified, the whole directory tree is excluded from the archive and from further directory scans. By default, star excludes the directory but still recursively scans the content of this directory as complex patterns could allow files inside the directory tree to match. Using -match-tree allows one to efficiently exclude whole trees from scanning. This helps to avoid scanning directory trees that are on remote file systems or contain excessive bad blocks.

maxsize=#

Do not store files in tarfile if they are bigger than #. See bs= for the possible syntax. By default, the number is multiplied by 1024, so the value counts in units of kBytes. If the size specifier ends with a valid multiplication character (e.g '.' for bytes or 'M' for MB) the specified size is used as specified and not multiplied by 1024. See bs= option for all possible multipliers.

-meta

In create mode, -meta causes star to archive all meta data of the file (e.g. uid, permissions, ...) but not the file content. In extract mode, it causes star to restore all meta data but not the file content. In addition, in extract mode no plain file, special file or directory will be created. Meta files are needed to support incremental backups.

Warning: Do not try to extract star archives containing meta files using other tar implementations if they are not aware of the meta file extensions of star. Star tries to force all tar implementations that are not standard compliant to abort. Star also tries to make all non POSIX.1-2001 compliant tar implementations unable to find a valid filename. However when other POSIX.1-2001 aware tar implementations come up and don't know about meta files, they will destroy files on disk.

The problems result from the only current fallback in the POSIX standard that tells tar implementations to treat all unknown file types as if they were plain files. As meta files are needed for incremental backups, I am looking for people and companies who like to support me to be able to add the meta file concept to the POSIX.1-2005 standard.

-modebits

This options allows you to create tar archives that include more than 12 bits from st_mode. Note this create tar archives that violate POSIX but some tar implementations insist in reading such nonstandard archives.

mtskip=#

Set the initial archive skip amount to #. See bs= for the possible syntax.

The archive skip size is the number of 512 byte blocks to ignore before starting to read the archive. Typically, the value printed by the -block-number option is used as the parameter.

This option is used if a tar archive on a tape is not read from the beginning in order to fast forward to a specific file. Check the -one-file option for a way to extract only one file from the archive.

If the archive is a plain file, this option results in a lseek() call to the input file. If the archive is a magnetic tape, this option results in a mtioctl(MTFSR) call for the part of the blocks that can be represented by the tape block size followed by a skip of the remainder of the blocks. Since star learns about the tape block size from the first read() call, this option does not work correctly if the tape block size used by star does not match the tape block size on the medium. See the blocks=# option above for information on the tape block size.

If mtskip=# has been specified, a iskip=# option is ignored and the value is rather computed from the mtskip=# parameter. mtskip=# does not work on compressed archives.

-multivol

Switch to multi volume mode. In multi volume mode, there will be no logical EOF marker written to the end of a single tape. If -multivol is used in read mode, a hard EOF on input (if not preceded by a logical EOF) triggers a medium change operation.

Specifying -multivol tells star to split files across volumes if needed. This way, a virtual archive is created that spans more than one medium. Multi volume mode is needed whenever it is not possible to split the archiving or extracting into several logically independent tasks. This is true for e.g. incremental dump/restore operations where inode numbers need to be traced for the whole task.

When tsize=# has been specified, but star is not in multi volume mode, files cannot be split across volumes.

When -multivol has been specified in create mode together with tsize=# then a media change is initiated exactly after an amount of tsize data has been written. When -multivol has been specified in create mode and tsize=# has not been specified, then the medium change is triggered by a EOT condition from writing the medium. This allows one to use media where the size cannot be known in advance (e.g. tapes with build in compression); it does not work if the EOT condition is not returned in sync with the related write operation. For this reason, it is expected that data buffering inside a device driver cannot be used.

Depending on the selected archive format, star writes a volume header at the beginning of a new medium. This medium header allows one to verify the correct volume after a change during read back. It is recommended to use the exustar format for best results. In create mode, -multivol is only supported for archives types that allow writing reliable multi volume header information.

See tsize=# option for more information.

Note that -multivol is an interactive option that prevents star from being used in non-interactive environments. If you like to use it in a non-interactive environment, you need to specify new-volume-script=script in addition in order to automate the media change procedure.

newer=filename

Do not store files to tarfile if their modification time is not newer than the modification time of filename. See -ctime option for changing this behavior.

-newest

In conjunction with the list command this lists you only the newest file in tarfile.

-newest_file

obsoleted by -newest-file

-newest-file

In conjunction with the list command this lists you only the newest regular file in tarfile.

new-volume-script=script

Call script at end of each tape (even the last one) if in multi volume mode or if the tsize= option has been specified. If this option is not in effect, star will ask the user to confirm the volume change. The script is called with two parameters. The first parameter is the next volume number and the second parameter is the next archive file name.

-nodump

If this option is set, star will not dump files that have the nodump flag set. Note that this currently only works on BSD-4.4 derivates and on Linux. On Linux, using this option will cause a performance degradation (the system time increases by 10%) because of the unlucky kernel interface that requires a separate open and ioctl.

-no-dirslash

Do not add a slash to the end of directory names if writing to an archive. Historic tar archive formats did only allow specifying plain files and hard links. Around 1980, BSD added a feature to specify a directory on tape by adding a slash to the end of the name. POSIX.1-1988 defined the first official tar archive format that had a clean method to specify the type of a directory. As old tar formats need the slash to recognize a directory, -no-dirslash may not be used if archives should be compatible with the old tar format.

-no_fifo

obsoleted by -no-fifo

-no-fifo

Don't use a fifo to optimize data flow from/to tarfile. Currently the -fifo option is used as default. (This may be changed at compile time.)

-no-fsync

Do not call fsync(2) for each file that has been extracted from the archive. Using -no-fsync may speed up extraction on operating systems with slow file I/O (such as Linux with any filesystem or platforms with Copy on Write filesystems like ZFS), but includes the risk that star may not be able to detect extraction problems that occur after the call to close(2). A typical cause for such problems is a NFS file system that fills up before the buffer cache is synced or a write error that occurs while the buffer cache is synced. There may be other reasons. Use with extreme care.

See also -do-fsync and STAR_FSYNC in ENVIRONMENT and /etc/default/star for ways to configure the default behavior.

-nochown, -o

Do not restore owner and group of files. This may be used if super user privileges are needed to overwrite existing files but the local ownership of the existing files should not change.

-no-p

Do not restore files and directories to their original permissions. This option is needed only if star is called by the super user and the permissions should not be restored from the archive. See also the -p option. The -p options has a higher precedence than the -no-p option.

-no_statistics

obsoleted by -no-statistics

-no-statistics

Do not print statistic messages at the end of a star run.

-no-secure-links

Extract hard links or symbolic links even if the target of the link starts with a slash (/) or if /../ is contained in the link target. See the description of the option -secure-links below and STAR_SECURE_LINKS in ENVIRONMENT and /etc/default/star for ways to configure the default behavior.

-no-xheader

Do not create or extract POSIX.1-2001 extended headers. This option may be used if you like to read an archive with broken extended headers.

-not, -V

Invert the meaning of the pattern list. i.e. use those files which do not match any of the pattern. Note that this option only applies to patterns that have been specified via the pattern=pattern or pat=pattern option. Patterns specified as file type arguments will not be affected.

-notarg, -pax-c

Match all file or archive members except those specified by the pattern or file operands.

-nowarn

Do not print warning messages. This sometimes is useful to make the output more readable (e.g. when hundreds of files that are going to be extracted are not newer in the archive then on the filesystem).

-numeric

Use the numeric user/group fields in the listing rather than the default. The default allows one to list the ASCII version of user/group of the file and to extract the owners of the files based on numeric values rather than the names. In create mode, no user/groups names are put on the archive. The -numeric option also applies when ACLs are going to be archived or extracted.

-O

Be compatible to old versions of tar. If star is invoked with this option, star generates archives which are fully compatible with old UNIX tar archives. If in extract mode, star ignores any additional info in the headers. This implies neither that archives generated with this option are binary equal with archives generated by old tar versions nor that star is trying to comprehend all bugs that are found in old tar versions. The bug in old tar versions that cause a reversal of a space and a NULL byte in the checksum field is not repeated. If you want to have signed checksums you have to specify the -signed-checksum option too. If you want directories not to be archived in order to be compatible to very old historic tar archives, you need to specify the -d option too.

This option is superseded by the H=headertype option.

-o, -nochown

Do not restore owner and group of files. This may be used if super user privileges are needed to overwrite existing files but the local ownership of the existing files should not change.

-one-file

Exit star after one file has been extracted as a result from a match with a pattern or with a command line argument. This option is intended for users that need to restore single files from larger tape archives and do not like to wait until the end of the tape is reached. To let star exit after the first file, call -one-file together with pat=*. This is e.g. useful together with the option mtskip=#.

-onull, -nullout

Do not actually write to the archive but compute and add the sizes. This is useful when trying to figure out if a tape may hold the current backup. Please only use the -onull option as it is a similar option as used by the sdd(1) command.

-P

Allow star to write a partial record as the last record. Normally, star writes each record with the same size. This option is useful on unblocked tapes i.e. cartridge tapes like QIC tapes as well as with archives that are located in files. If you use this option on local files, the size of the archive will be smaller. If you use this option on cartridge tapes, is makes sure that later - in extract mode - star will read up to the end of file marker on the tape and the next call to star will read from the next archive on the same tape.

-p

Restore files and directories to their original permissions. Without this option, they are created using the permissions in the archive and the present umask(2). If star is called by the super user, star behaves as if it has been called with the -p option. See also -no-p option. If the archive contains Access Control Lists (ACLs) in POSIX.1-2001 extended headers, star will restore the access control lists from the archive for files if the -acl option is specified. If the option -acl has not been specified, ACLs are not restored at all.

-partial

Force an incremental restore even if the incremental dump is only a partial dump. See -wtardumps, level= and sections INCREMENTAL BACKUPS and INCREMENTAL RESTORES for more information.

pattern=pattern, pat=pattern

Set matching pattern to pattern. A maximum of 100 pattern=pat options may be specified. As each pattern is unlimited in length, this is no real limitation. If more than one pattern is specified, a file matches if any of the specified pattern matches. Patterns may be used in create mode to select or exclude files from the list of file type arguments or the files located in a sub tree of a file type argument directory. By default, star scans the whole directory tree underneath a directory that is in the argument list. This may be modified by using the -match-tree option. In extract or list mode, all file type arguments are interpreted to be select pattern and all option type patterns may be either select or exclude patterns depending on the presence or absence of the -not option. If you use file type select patterns, they work exactly like the method used by other (non pattern aware) tar(1) implementations. File type select patterns do not offer pattern matching but allow restoring subtrees. To extract a complete sub tree from the directory dir with star using the pattern= option, use pattern= dir/ if you like to select a subtree by using the historic method, use dir as file type argument. If you only like to extract the directory itself, use dir/ as file type argument. See manual page for match(1) for more details of the pattern matcher. All patterns are selection patterns by default. To make them exclude patterns, use the -not or the -V option.

pkglist=file

This is (for now) an internal interface for the Schily Source Package System (sps). It only works in create mode and behaves similar to the list= option, but it allows one to overwrite the permissions, the uid and gid values from the content of the pkglist= file. Each line from the pkglist= file contains a file name followed by the permission, a user name and a group name. The permission is an octal character string. Each value that is not used to overwrite the original values may be replaced by a '?'. The fields are separated by spaces, so the pkglist= option does not allow files that contain newline or space characters.

If used together with -find, the uid, gid and permission values from the pkglist=file have precedence over changes on this meta data introduced by libfind.

See list= option for further information.

-pax-c, -notarg

Match all file or archive members except those specified by the pattern or file operands.

-pax-H

Follow symbolic links that have been encountered on the command line. If the referenced file does not exist, the file information and type will be for the link itself. If the link is referencing a file type that cannot be archived with the current archive format, the file information and type will be for the link itself.

-pax-i

Do interactive renaming in a way that has been defined for POSIX pax. Star will print the original filename and prompt for a reply. If you type just RETURN, than the file is skipped. If you type '.', then the original file name is retained. If you type anything else, then this is taken as the new file name.

Note that -pax-i is an interactive option that prevents star from being used in non-interactive environments.

-pax-L

Follow symbolic links. If the referenced file does not exist, the file information and type will be for the link itself. If the link is referencing a file type that cannot be archived with the current archive format, the file information and type will be for the link itself.

-pax-ls

Switch listing format to the format defined for POSIX pax and ls.

-pax-match

Allow file type arguments to be recognised as regular expressions in a way that has been defined for POSIX pax.

-pax-n

Allow each pattern to match only once. If a pattern matches a directory, then the whole sub tree matches the pattern.

-pax-o string

Set a pax like option control pattern.

The only argument that is currently supported is binary to create a hdrcharset=BINARY header.

-pax-p string

PAX style privileges string. Several characters (each has its own meaning). The following characters are defined:

-pax-s replstr

Modify file or archive member names named by a pattern according to the substitution expression replstr. The format of replstr is:

-pax-s /old/new/[gp]

The old pattern may use regular expressions and the new string may contain the special character '&'. The character '&' is substituted by the string that matches the old pattern. The new string may also contain the special strings '\1' .. '\9' that refer to parts of the old string selected by '\(...\)' groups. The optional trailing 'g' means global substitution. If 'g' is not used, a substitution pattern is only used once on a name. If the optional trailing 'p' is used, the substitution is printed to standard error.

Up to 100 substitute options may be used. If more than one substitute option has been specified, star will loop over all substitute patterns until one matches. The up to 100 substitute options are processed together with the -s replstr options in the order they appear on the command line.

If the name substitutes to the empty string, the file is skipped.

If the target platform for star does not support regex functions, there is a silent fallback to the -s replstr option and the '\1' .. '\9' substitutions are not possible.

-prinodes

Print inode numbers in verbose list mode if the archive contains inode numbers.

-print-artype

Check the type of the archive, print the archive and compression type on a single line and exit.

-qic24

Set tape volume size to 61440 kBytes. See tsize=# option for more information.

-qic120

Set tape volume size to 128000 kBytes. See tsize=# option for more information.

-qic150

Set tape volume size to 153600 kBytes. See tsize=# option for more information.

-qic250

Set tape volume size to 256000 kBytes. See tsize=# option for more information.

-qic525

Set tape volume size to 512500 kBytes. See tsize=# option for more information.

-read0

Read null terminated file names from the file specified with the list= option.

-refresh_old_files

obsoleted by -refresh-old-files

-refresh-old-files

-refresh

Do not create new files. Only already existing files may be overwritten from tarfile if either newer versions are present in the archive or if the -U flag is used. This allows one to overwrite files by more recent files from an archive that contains more files than the target directory should contain. The option -refresh-old-files is the same as the -refresh option.

-remove_first

obsoleted by -remove-first

-remove-first

Remove files before extraction. If this option is in effect, star will remove files before extracting a file from the archive. This is needed if you want to change the file type or if you need to break a hard link. If you do not use either -ask-remove or -force-remove together with -remove-first, this option is useless and no files will be removed.

-remove_recursive

obsoleted by -remove-recursive

-remove-recursive

Remove files recursive. If removing of a file is permitted, star will only remove files, specials and empty directories. If this option is in effect, star will be allowed to recursively removes non empty directories too.

-restore

switches star into true incremental restore mode. A file named star-symtable and a directory named star-tmpdir is created in the root directory of the file system where the extraction takes place. If -restore has been specified, star behaves as if -xdot has been specified too. See also level= option and section INCREMENTAL BACKUPS for more information.

Note: Do not use the -restore option if you only like to restore a single file or a list of selected files.

rmt=path

Specify the path to the program at the remote tape server for the RMT protocol.

star by default calls the UNIX default path /etc/rmt.

Since most rmt implementations cause problems in case that server and client are on a different OS, it is recommended to tell star to call the rmt program that comes with star (/opt/schily/sbin/rmt).

rsh=path

Specify the program to log into the remote tape server for the RMT protocol. If the argument is the empty string, connections are made via rcmd(3). The default method to log into the remote server is configurable at compile time. The current default is set up to use ssh.

-S

Do not store/create special files. A special files is any file except plain files, symbolic links and directories. You need to be super user to extract special files.

-s replstr

Modify file or archive member names named by a pattern according to the substitution expression replstr. The format of replstr is:

-s /old/new/[gp]

The old pattern may use regular expressions and the new string may contain the special character '&'. The character '&' is substituted by the string that matches the old pattern. The optional trailing 'g' means global substitution. If 'g' is not used, a substitution pattern is only used once on a name. If the optional trailing 'p' is used, the substitution is printed to standard error.

Up to 100 substitute options may be used. If more than one substitute option has been specified, star will loop over all substitute patterns until one matches. The up to 100 substitute options are processed together with the -pax-s replstr options in the order they appear on the command line.

If the name substitutes to the empty string, the file is skipped.

-secure-links

Do not extract hard links or symbolic links if the target of the link starts with a slash (/) or if /../ is contained in the link target. Tar archives containing such links could be used to compromise the system. If they are unpacked together with a lot of other files, this may not even be noticed.

Links that do not point outside the tree that starts with the current working directory are not seen as a security risk. This makes star easy to use. It is always safe to unpack an unknown archive in an empty directory.

Many system installations contain plenty of symbolic links with absolute path name or with /../ inside. The usability of a tar archiver for system backups and in copy mode would be limited if -secure-links checking would be done by default for backups or when in copy mode, star thus makes link checking optional when in -restore or in -copy mode. When neither -restore nor -copy have been specified, link checking is the default, since this is the usual way when archives from unknown sources are going to be unpacked.

To turn off this default for the usual case, the option -no-secure-links may be used and in -restore or -copy mode, -secure-links may be specified to turn it on.

If you unpacked a tar archive while -secure-links is effective and did not get a security warning at the end of the star run, all files and links have been extracted. If you get a warning, you should unpack the archive a second time and specify the options -k, -w and -nowarn in addition to the options used for the first run. To speed this up, it helps to use:

star -xvpw -find -type l

See section SECURITY NOTES for more information and STAR_SECURE_LINKS in ENVIRONMENT and /etc/default/star for ways to configure the default behavior.

-shm

Use System V shared memory for fifo. Normally star is compiled to use mapped /dev/zero pages for the fifo, if the operating system supports this. If star is compiled to have both code for mapped pages and for System V shared memory, star will use shared memory instead of the default. If the -help menu doesn't show the -shm flag you have no choice. When using System V shared memory, you may have to raise the system's internal limit for shared memory resources to get enough shared memory for star.

-signed_checksum

obsoleted by -signed-checksum

-signed-checksum

Use signed chars to calculate checksums. This violates the tar specs but old versions of tar derived from the seventh edition of UNIX are implemented in this way. Note: Only filenames and linknames containing chars with the most significant bit set may trigger this problem because all other fields only contain 7 bit ASCII characters, octal digits or binary zeroes.

-silent

Suppress informational messages like foobar is sparse.

-sparse

Handle files with holes effectively on store/create. Note that sparse files may not be archived this way if the archive format is tar, ustar, suntar, pax, or any cpio variant. On Solaris-2.3 ... Solaris-2.5.1 there is a special ioctl() called _FIOAI that allows root to get the allocation info more efficiently. On Solaris 11 there is an enhanced lseek(2) call with additional whence values SEEK_HOLE and SEEK_DATA that allow finding holes in an efficient way. Other operating systems lack support to get the real allocation list and force star to scan the files to look for blocks that only contain null characters. This may star cause to assume more holes to be present than the number that the file really contains.

-symlinks

This option tells star in extract mode to try to create a symlink whenever a hardlink is encountered in the archive.

-T

If the option file= or f= is omitted and the -T option is present, star will use the device indicated by the TAPE environment variable, if set.

tardumps=name

Set the file name for tar dump dates database to name. The default name is /etc/tardumps. Use in combination with the level= option to create true incremental dumps. See also -wtardumps option and section INCREMENTAL BACKUPS for more information.

-time

Print timing info. See DIAGNOSTICS for more information.

-to_stdout

obsoleted by -to-stdout

-to-stdout

Extract files to stdout. This option may be used to extract tarfiles containing tarfiles (see examples below).

-tpath

Use this option together with the -t option or with -cv (verbose create) to get only a list of the pathnames of the files in the archive. This may be used in shell scripts to generate a name list. If used together with the -diff option, star will only print the names of the files that differ. A second run of star may then be used to restore all files that had differences to the archive. Use the list= option to specify the namelist in this case.

tsize=#

Set tape volume size to # to enable multi volume tape support. The value refers to the archive size without compression. See bs= for the possible syntax. By default, the number is multiplied by 512, so the value counts in units of 512 byte blocks. If the size specifier ends with a valid multiplication character (e.g '.' for bytes or 'M' for MB) the specified size is used as specified and not multiplied by 512. With this option in effect, star is able to archive filesystems that are bigger then the tape size. If the option tsize=# without -multivol then no file will be split across volumes and each volume may in theory be read back separately. Files that do not fit on a single tape may not be stored in this mode. If -multivol has been specified in addition, star will split files when the maximum allowed tape size has been reached. If the tape volume size is not a multiple of the tape block size, the tape volume size is silently rounded down to a value that is a multiple of the tape block size.

See -multivol option for more information.

-U

Restore files unconditionally. By default, an older file from the archive will not replace a corresponding newer file on disk.

umask=mask

Set star's umask to mask. This allows one to control the permissions for intermediate directories that are created by star in extract mode. See also -p option.

-uncond-rename

When in interactive restore mode or when the -s option was specified, unconditionally ask for a new name or apply a substitution. This happens even when the current path name would be skipped otherwise because the file in the archive is not newer than the file with the original name on disk.

-v

Increment verbose level by one. This normally results in more output during operation. See also in the description for the -t flag. Normally, star does its work silently. If the verbose level is 2 or more and star is in create or update mode, star will produce a listing to the format of the ls -l output.

-V, -not

Invert the meaning of the pattern list. i.e. use those files which do not match any of the pattern. Note that this option only applies to patterns that have been specified via the pattern=pattern or pat=pattern option. Patterns specified as file type arguments will not be affected.

-version

Print version information and exit.

VOLHDR=name

Use name to generate a volume header.

-w

Do interactive creation, extraction or renaming. For every file that matches the list of patterns and that has a more recent modification time in the tar archive (if in extract mode and the -U option is not specified) star prints its name and asks:

-wready

This option tells Star to wait up to two minutes for the drive to become ready. It has been added as a hack for a bug in the SunOS/Solaris st device driver. This driver has problems to sense the loading time with Exabyte drives with factory settings. It also makes sense to use -wready if multiple remote backups are made. In this case, the remote connection is closed while the remote tape server is still writing a file mark. If another remote backup is initiated before the old remote server did finish to write the file mark, it would be impossible to open the tape driver unless -wready is specified to tell star to wait for the drive to become ready again.

-wtardumps

Tell star to update the file that contains the tar dump dates data base if in dump mode. If the dump is not a full dump, the tar dump dates data base file is not written. See also tardumps=name and -C option or INCREMENTAL BACKUPS section for more information.

-X filename

Use the file filename as a file containing a list of path names to be excluded from the store/create/list/diff operation. The file filename must contain a list of path names, each on a separate line. Be careful with white space and note that path names in the list may not contain new lines. Multiple -X options may be used. Each argument must refer to a file containing path names. The -X option has precedence before other options that select files to be included in the operation. See also list= option.

-xattr

Reserved for NFSv4 extended attributes.

-xattr-linux

Store and extract extended file attributes as found on Linux systems. This option only makes sense when creating or extracting exustar archives as it is based on POSIX.1-2001 extended tar headers.

The method used in the current implementation could be used to store and extract extended file attributes from BSD too. Note that the current implementation is not generic enough to cover more general extended file attribute implementations as found on Solaris. If star starts to implement a method that covers extended file attributes on Solaris, the new method will be used then -xattr has been specified and -xattr-linux will refer to the old method. The method used with -xattr-linux may go away in the future.

-xcopy

An alias for -copy -sparse -acl

xdebug=#, xd=#

Set extended debug level to #.

-xdev, -M

Do not descend mount points. This is useful when doing backups of complete file systems. See NOTES for more information.

When using -find, this may not always work as expected, e.g. when the /proc filesyestem is involved. Use -xdev past -find for this reason.

-xdir

Extract directories even if the corresponding directories on the archive are not newer. This is useful when for some reason, the directories are recorded after their content (see -dirmode option), or when the permissions of some directories must be set in any case. As the classical UNIX cpio program does not implement delayed directory permission and time stamp setting, cpio users often create archives in reverse order (directories past their content). For this reason, it makes sense to use -xdir while extracting cpio archives.

-xdot

Unconditionally extract the first directory in the archive if the name of this directory is either '.' or './'. This helps to extract archives in an expected way if the target directory is a newly created empty directory. As this directory is newer than the top level directory in the archive, star would usually skip this directory during extraction. The effect of this directory is as if -xdir has been specified but is switched off after the first directory has been found.

-xfflags

Store and extract extended file flags as found on BSD and Linux systems. This option only makes sense when creating or extracting exustar archives as it is based on POSIX.1-2001 extended tar headers. See NOTES section for problems with -xfflags on Linux systems.

-xmeta

Extract meta files as if they were files. Meta files in archives are plain files that do not contain any content data in the archive. They may be created by using the -meta option in star's create mode. Existing files are not overwritten. If a file is missing, a zero sized file is created. If the option -meta is used together with the option -force-hole, missing plain files are created as sparse empty files of the original size.

-xz

Run the input or output through a xz pipe. See section COMPRESSION for details.

-Z

Run the input or output through a compress pipe. See section COMPRESSION for details.

-z

Run the input or output through a gzip pipe. See section COMPRESSION for details.

-zstd

Run the input or output through a zstd pipe. See section COMPRESSION for details.

COMPRESSION¶

In most cases, star automatically detects compressed archives and executes an appropriate decompression program to assist it in extracting files from the archive. The compressed archive is first passed to standard input of the decompression program. Star reads the decompressed archive from standard output of the decompression program and processes it as usual.

If the creation of a compressed archive is desired or if this mechanism fails, the option compress-program=name can be used to configure name as a compression/decompression helper. Options -7z, -bz, -freeze, -j, -lzip, -lzma, -lzo, -xz, -Z, -z, and -zstd are available as shorthands for the most common compression/decompression helpers. For all of these helpers, star is capable of detecting that a compressed file needs one of them to be decompressed automatically.

Compression and decompression helpers are expected to be filters reading from standard input and writing to standard output. By default, star passes the sole option -d to a decompression helper. Compression helpers are started without any options. Helper commands and options can be overridden using the name_CMD options in sections [compress] and [decompress] of /etc/default/star. See section FILES for details.

If the environment variable STAR_COMPRESS_FLAG is set, its contents are appended to the argument list for compression helpers. This is useful to pass a compression level to programs like gzip(1).

INCREMENTAL BACKUPS¶

Star is able to back up file system in full and incremental mode. To allow incremental backups, the file system must implement POSIX semantics.

To be more verbose:

•

The filesystem needs to uniquely identify files by the two numbers st_dev (The filesystem ID or device ID of the device containing the file) and st_ino (The file serial number). If a file is renamed, these numbers need to be retained. Both numbers need to be a cardinal scalar that is expressible in a decimal number.

•

The filesystem needs to implement at least two time stamps, st_mtime the file's last modification time and st_ctime the file's last status change time. Both time stamps need to be dealt with as documented by the POSIX standard. Both numbers need to be a cardinal scalar that is expressible in a decimal number or as a decimal number that counts in seconds plus another number that counts in fractions of a second.

•

The filesystem needs to allow renaming files and directories by either calling rename(2), or link(2) and unlink(2).

•

The filesystem needs to honor and preserve the case of file names.

The incremental backup method used by star depends on comparing the time stamps of all files against the time of the last backup. Note that this method only works correctly if the level 0 backup and all higher level incrementals include the whole file system. As star archives all inode meta data, star is able to detect renamed files by comparing the inode numbers of all files while in incremental restore mode.

Detecting renamed files only works if star, while in backup mode, scans the whole file system tree for each full and incremental backup. This will work in case no files are excluded and the dump starts at the root directory of a file system. In case that no files are renamed from excluded parts to included parts, partial backups may be taken also. Partial backups only make sense if a complete directory sub tree is excluded (e.g. by using the pat= option) or if a partial backup starts at a sub directory that is not the root directory of the file system.

In case of a partial backup, it is important that no file or directory will ever be moved outside the scope and later move into the scope again. Moving files or directories outside the scope of a partial backup is detected as deletion and moving the files back into the scope does not make them appear in an incremental backup since the time stamps of files from inside renamed directories did not change.

Note that a backup must not include files that are mounted from another filesystem and a restore cannot be done with more than one filesystem as target.

Files in the backup tree that are hidden under a mount point cannot be part of the backup as long as the backup is not done from a snapshot.

To create a level 0 dump call:

star -c -xdev -sparse -acl -link-dirs level=0 -wtardumps \
    f=archive-name -C /filestem-mount-point .

To create a level 1 dump call:

star -c -xdev -sparse -acl -link-dirs level=1 -wtardumps \
    f=archive-name -C /filestem-mount-point .

Do not forget the dot at the end of the command line that specifies the directory to start the operation.

Backups from live filesystems should be avoided. On operating systems that support file system snapshots, backups should be made from a read-only mount of a snapshot. Be careful that all files that have been created between setting up a snapshot and starting an incremental backup may be missing from all backups unless the dumpdate=name option is used.

If the system that is going to be backed up is not acting as a file server, it makes sense to shut down all services that may result in inconsistent file states before setting up the filesystem snapshot. After the filesystem snapshot has been set up, the services may be restarted.

If the the system that is going to be backed up is acting as a file server, it may be that services on remote clients cause inconsistent file states unless all such services that remotely access files are shut down before the snapshot is set up.

Star includes options that help to deal with file system snapshots. The following example backs up a file system on Solaris using a file system snapshot from UFS:

echo > /tmp/snapstamp

mount -r `fssnap -F ufs -o \
    backing-store=/var/tmp/EXPORT-NFS.snap /export/nfs` /mnt

star -c -xdev -sparse -acl -link-dirs level=0 -wtardumps \
    f=archive-name dumpdate=/tmp/snapstamp \
    fs-name=/export/nfs -C /mnt .

First a file with a current time stamp is created, then a snapshot for /export/nfs is created and mounted on /mnt. The following star command then creates a level 0 backup from the file system using the time the snapshot was created and the original mount point of the file system for /etc/tardumps and the archive header.

Note that if the backup is done on a live file system, it may be unreliable. A typical problem problem in this context is caused by growing log files. As growing files are not a real problem with backups, the best way of dealing with growing files is to set up a star error control file (see errctl= option) and to tell star to ignore growing files.

BACKUP SCHEDULES¶

Full (level 0) dumps should be made on a regular base (e.g. once a month). As a full dump may take a long time and takes a lot of tape, it is wise to make higher level incremental dumps with shorter intervals. The next table shows a dump level list that may be used if monthly full dumps take place:

	Sun 	Mon	Tue	Wed	Thu	Fri
Week 1:	0	10	10	10	10	5
Week 2:	10	10	10	10	10	5
Week 3:	10	10	10	10	10	5
Week 4:	10	10	10	10	10	5

The level 10 dumps made between Monday and Friday accumulate all changes made within the week, but you only need to restore the latest level 10 dump in order to get all changes back. If you don't like the size of the accumulated changes, use the following backup schedule:

	Sun 	Mon	Tue	Wed	Thu	Fri
Week 1:	0	20	30	40	50	5
Week 2:	10	20	30	40	50	5
Week 3:	10	20	30	40	50	5
Week 4:	10	20	30	40	50	5

Note that in this case, 7 dumps need to be restored if the a crash happens at the worst case date (just before the Friday dump in week 2 or later).

INCREMENTAL RESTORES¶

Incremental restores should be made to an empty file system (except for the lost+found directory). Star is currently unable to perform incremental restores to a file system that contains active mount points.

Incremental restores should be run as root user. Star supports private incremental dumps and restores run as an unprivileged user, but this mode has been tested less frequently.

The incremental restore procedure starts with restoring the last full (level 0) dump. Then the latest incremental dump of each dump level (with ascending order of dump levels) need to be restored.

Let us assume the first example from the section BACKUP SCHEDULES for the backup schedule. If a disk crash happens before the Thursday dump of week 3 has been made, the following restore procedure needs to be applied:

level 0

starting with an empty disk, the full (level 0) dump from week 1 is restored.

level 5

after the level 0 restore has been finished, the level 5 dump from Friday in week 2 is restored.

level 10

after the level 5 restore has been finished, the level 10 dump from Wednesday in week 3 is restored.

The disk now contains the same files as it did when the level 10 dump has been made on Wednesday of week 3.

To extract a level 0 dump call:

cd /extract-filestem-mount-point
star -xpU -restore f=archive-name

This creates the directory star-tmpdir and the database star-symtable in the root directory of the new file system. Subsequent restores with higher level backups depend on these files.

To extract a level 1 (or higher) dump call:

cd /extract-filestem-mount-point
star -xpU -restore f=archive-name

In order to restore a partial dump, the -partial option needs to be specified. This is to make sure that the user understands that renames to a path outside the scope of the partial dump may result in inconsistencies during a restore.

In case there is a dump level mismatch or a reference date mismatch, it is possible to give a restore a chance by specifying the -force-restore option.

Note that the environment variable STAR_DEBUG exists, star does not remove files with link count 1 that have been removed between incremental dumps. These files are moved to the directory star-tmpdir. Before you start to extract the next incremental, you need to remove all files in star-tmpdir.

SYNCHRONIZING FILESYSTEMS¶

Star may be used to synchronize filesystem content. To do this, an initial copy of the current content of the source filesystem needs to be performed first.

To create an initial copy of a filesystem call:

star -c -xdev -sparse -acl -link-dirs level=0 -wtardumps \
    -C /filestem-mount-point . | \
    star -xpU -restore -C /extract-target-dir

In order to perform subsequent synchronization of the target filesystem with the content of the source filesystem, a modified incremental dump/restore procedure may be used.

To copy incremental content of a filesystem call:

star -c -xdev -sparse -acl -link-dirs level=1 -wtardumps \
    -cumulative -C /filestem-mount-point . | \
    star -xpU -restore -C /extract-target-dir

Note that like with backups in general, copies from a live filesystem should be avoided. On operating systems that support file system snapshots, copies should be made from a read-only mount of a snapshot. Be careful that all files that have been created between setting up a snapshot and starting an incremental copy may be missing from all copies unless the dumpdate=name option is used.

See section INCREMENTAL BACKUPS to learn how to modify the command line in case file system snapshots are used.

SIGNALS¶

If star handles a signal, it first prints the statistics. Star handles the following signals:

SIGINT

usually generated by ^C from the controlling tty. Upon receipt of a SIGINT, star prints statistics and exits. If in create mode i.e. storing files to archive, star finishes with the current file to ensure that no partial file is written to the archive, write an eof record and then exits.

SIGHUP

not to be generated from a tty. The actions are the same as upon receipt of a SIGINT.

SIGQUIT

SIGINFO

usually generated by ^\ from the controlling tty. Upon receipt of a SIGQUIT, star prints statistics and continues with the current operation. This is useful to watch the progress of the current operation.

EXIT STATUS¶

The following exit values are returned. Note that the negative values are only available to modern shells and programs that use waitid(2) on a POSIX OS and thus can retrieve the full 32 bits of the star exit code. The positive number variants are what you get when only the low 8 bits from the exit code are available.

0

All files were processed successfully.

-64 / 192

An exit code has been used that does not fit into an 8-bit unsigned number and the environment COMERR_EXCODE has not been set. The value -64 / 192 in this case marks a clash.

-4 / 252

Star has been interrupted in create mode and the end of star has been delayed until the current file has been archived completely. This error is only used in case that no other error occurred and the tar archive only has become shorter than expected.

-3 / 253

Star has been called with the option -e, or the errctl= option has been used to mark the current error fatal.

-2 / 254

One or more files could not be processed successfully.

-1 / 255

Command line parsing error.

>0

Other positive exit codes: The errno of the call that caused the fatal error.

EXAMPLES¶

To get a listing in a way similar to ls -l one might use:

example% star -tv f=/dev/rmt/1bn

The same command as listed above in a POSIX tar command line syntax compliant way is:

example% star tvf /dev/rmt/1mbn

To copy the directory tree in /home/someuser to the directory /home/fs use:

example% (cd /home/someuser; star -c .) | (cd /home/fs ; star -xp)

or by using the change directory option of star:

example% star -c -C /home/someuser . | star -xp -C /home/fs

Note that both examples above are not the optimum way to copy a directory tree. A more efficient way to copy a directory tree is to use the -copy option.

example% star -copy -p -xdot -C /home/someuser . /home/fs

To copy a file tree including the Access Control List entries for all files and to correctly copy sparse (holey) files use:

example% star -copy -p -xdot -acl -sparse -C /home/someuser . /home/fs

To compare the content of a tape to the filesystem one might use:

example% star -diff -v f=/dev/rmt/1bn

To compare two directory trees one might use:

example% star -c . | star -C todir -diff -v diffopts=!times

or better by using a method similar to the -copy method above:

example% star -c -diff -v diffopts=!times -C fromdir . todir

To compare all properties of two file trees, use:

example% star -c -diff -vv -dump -acl -sparse -C fromdir . todir

To extract a backup of the /usr tree without all files residing below /usr/openwin one might use:

example% star -xp -V pat=openwin/\* f=/dev/rmt/1bn

To extract all .c files to src, all .o files to obj and all other files to /tmp one might use:

example% star -xp -C src '*.c' -C obj '*.o' -C /tmp '*' f=/dev/rmt/1bn

To extract files from a zipped tar archive that is located on a read only filesystem e.g. a CD while having the shell's working directory on the CD one might use:

example% star -zxp -C /tmp f=star-1.1.tar.gz

to extract the files from the tar archive to the /tmp directory.

To backup a list of files generated by the find(1) command:

example% find . find_options -print | star -c list=- f=/dev/rmt/1bn

Note that this does not work if the file names from output of the find command include new line characters.

To extract a tarfile that contains a tarfile one might use:

example% star -x -to-stdout f=/dev/rmt/1bn pat=pat | star -xp

Pat, in this case should match the tarfile in the tarfile on tape that should be extracted.

To make a backup of the root filesystem to a tape drive connected to a remote machine, one might use:

example# cd /

example# star -cM fs=128m bs=63k f=tape@remotehost:/dev/rmt/1bn .

You need a line in /etc/passwd like the following to enable this:

tape:NP:60001:60001:Tape:/etc/tapehome:/opt/schily/sbin/rmt

And a .rhosts file in /etc/tapehome to allow remote connections from the appropriate hosts. Make sure that the file /etc/default/rmt exists and allows remote access to the requested tape drive.

To use a faster rcmd(3) connection for a backup to a remote tape server, one might use:

example# env RSH='' star -cM fs=128m bs=63k f=tape@remotehost:/dev/rmt/1bn .

Note that this requires root privileges.

To repair a corrupted filesystem for which no recent backup exists, do the following:

example# fsck -y /filesys
example# mount /filesys
example# cd /filesys
example# star -xpk f=/dev/rmt/1bn
example# mt -f /dev/rmt/1bn rewind
example# star -diff -v diffopts=!times f=/dev/rmt/1bn

Now check the differences and decide whether to restore additional files. This may be done by generating a list containing the needed filenames and using the list= option or by using the interactive mode (see -w option).

If you want a list that only contains all filenames from files with differences you may use:

example# star -diff -tpath diffopts=!times f=/dev/rmt/1bn

If you are looking for files that changed the type or the access permission because this is a common case on still corrupted files, use:

example# star -diff -tpath diffopts=type,perm f=/dev/rmt/1bn

If you like to archive all directories only that are part of the directory tree under ".", use:

example# star -c f=archive-name -find . -type d

If you like to archive all files as owner root and group root and make all files world readable in the archive, use:

example# star -c f=archive-name -find . -chown root -chgrp root -chmod o+r

If you like to archive all files with a mtime of now, use:

example# star -c f=archive-name -find . -chmtime now

If you like to list all files in an archive in a way like sfind(1), instead of the way used by star, use:

example# star -t f=archive-name -find . -ls -false

If you like to split the content of an archived tree into tar chunks of 1 GB, you could call:

example# star -c f=/tmp/v.tar tsize=1G \



new-volume-script='sh -c "mv /tmp/v.tar /tmp/v$(($1-1)).tar" nv' .

ENVIRONMENT¶

COMERR_EXCODE

If this environment is present, exit codes are not mapped to avoid possible clashes with calling programs that use the outdated waitpid(2) instead of the waitid(2) call to wait for the exit status from star. While waitid(2) returns the full 32 bit exit code, waitpid(2) masks the exit code with 0377. Without the environment COMERR_EXCODE, exit codes outside the range -63 .. 191 are mapped to -64 (192) to mark a clash.

If the environment COMERR_EXCODE is set and the value starts with the character '0', an exitcode code > 0 that leads to exitcode & 0377 == 0, is mapped to -64 to avoid confusion with shells that use waitid(2) but interpret these exit codes as zero with respect to conditional execution in order to implement compatibility to historical shells.

With a shell that supports the full exitcode on and a POSIX compliant operating system, it is recommended to set the environment COMERR_EXCODE.

STAR_COMPRESS_FLAG

If you like star to always create compressed files that use maximum compression, you may set the environment variable STAR_COMPRESS_FLAG to -9.

STAR_DEBUG

If this environment variable is present, star will not remove temporary files from ./star-tmpdir. The files in this directory are files that have been removed by users before the last incremental dump did take place on the master filesystem.

STAR_FIFOSIZE

If you like to by default let star use a different fifo size, set this environment variable to the desired size.

STAR_FSYNC

If set to `N', the default behavior of star is as if the -no-fsync option has always been specified.

This grants that star is always faster than other archivers, but makes it impossible for star to check whether the extraction of a file to the filesystem was successful.

If set to any other value, the default behavior of star is as if the -do-fsync option has always been specified.

The environment STAR_FSYNC has precedence over /etc/default/star but may still be overwritten by command line options.

STAR_NOHINT

If this environment is seen, some informative messages are not printed. this currently applies to messages related to STAR_FSYNC and STAR_SECURE_LINKS.

STAR_SECURE_LINKS

If set to `N', the default behavior of star is as if the -no-secure-links option has always been specified.

This disables checks for potentially insecure links by default.

If you like to make this the default, keep in mind that you need to specify -secure-links in case you like to unpack an archive from unknown sources.

The environment STAR_SECURE_LINKS has precedence over /etc/default/star but may still be overwritten by command line options.

STAR_WORKAROUNDS

If this environment variable is present, implement workarounds for named problems. The environment variable is expected to contain a comma separated list of bug names:

TAPE

Unlike other tar(1) implementations, star defaults to use stdin/stdout for the archive. If you like star to use the file name from the TAPE environment instead, you need to specify the -T option too.

RSH

If the RSH environment is present, the remote connection will not be created via the default method, but rather uses the program specified by RSH. Use e.g. RSH=/path/to/ssh to create a secure shell connection using a specific ssh version.

If the RSH environment is not present, the compiled in default is used. This currently is ssh.

If the RSH environment is empty, then rcmd(3) is used.

Former versions of star by default did use rcmd(3) to create a remote connection. Using a different method forces star to create a pipe to the rsh(1) or ssh (1) program and disallows star to directly access the network socket to the remote server. This makes it impossible to work at maximum performance and slows down the connection compared to a root initiated rcmd(3) connection.

See rsh= option for more information.

See BUGS section for more information.

RMT

If the RMT environment is present, the remote tape server will not be the program /etc/rmt but the program pointed to by RMT. Note that the remote tape server program name will be ignored if you log in using an account that has been created with a remote tape server program as login shell.

See rmt= option for more information.

FILES¶

/etc/default/star

Default values can be set for the following options in /etc/default/star. For example: CDR_FIFOSIZE=64m

/etc/tardumps

The default name for the dump level archive. The default name is used whenever the tardumps=name option has not been specified. The file is written or updated when -wtardumps is used.

The file holds one or more lines, each specifying a dump level entry. Each dump level entry starts with a mount point name followed by a TAB and one or more spaces, followed by the decimal dump level, a space and the dump time.

If the dump level is directly followed by a 'P', then the dump refers to a partial dump (a dump that does not include the whole filesystem).

The dump time itself includes the decimal representation of the UTC seconds since Jan 01 1970, a space and the textual local time representation of the dump time.

The numerical decimal dump time representation may be followed by a dot and a sub second value. The textual local time representation is for informational use by humans only and not evaluated by star.

./star-symtable

Contains a database that is needed in incremental restore mode.

./star-symdump

Contains an intermediate dump of restore database after a fatal error condition was met during an incremental restore operation.

./star-tmpdir

Is the temporary directory that is used as intermediate file storage by star if in incremental restore mode.

./star-lock

Is a lock file created by star when doing an incremental restore. If this file is present, it prevents star from running another incremental restore operation. This helps to avoid more than one restore operation at a time (e.g. from a cron script).

/dev/tty

Is used for the interactive user interface.

SEE ALSO¶

spax(1), suntar(1), scpio(1), tar(1), cpio(1), pax(1), rcp(1), mt(1), rmt(1), match(1), dd(1), sdd(1), rsh(1), ssh(1), star_sym(1), tartest(1), star(5), rcmd(3), fssnap(1m), waitid(2), waitpid(2)

DIAGNOSTICS¶

star: f records + p bytes (total of x bytes = d.nnk).

The number of full records, the number of bytes in partial records and the total amount of data in KBytes.

star: Total time x.yyysec (z kBytes/sec)

The time used and the transfer speed from/to the archive.

If there have been non fatal errors during the archive processing, star will display a delayed error summary before exiting.

NOTES¶

The command line syntax for the tar command (as defined in SUSv2 - UNIX-98) deviates from the command line syntax defined for all other commands. While the POSIX command line syntax requests all options to start with a dash (-) and allows one to either write options separately or combined (in case of boolean flags), the tar command line syntax requires all options to be combined into a single string that does not start with a dash. Star by default assumes a command line syntax like a typical POSIX command and includes a compatibility mode that allows one to specify a command line syntax as documented for the UNIX-98 tar command. If you believe that you found a bug in the way star parses the command line, please first check your command line for correctness before you make a bug report for star.

If you like to write portable shell scripts that call tar, use the UNIX-98 tar command line syntax (i.e. a single option string and no dash), choose the commands and options from the following set of characters ( rxtuc vxfblmo ) and check the shell script with both, your local tar and star for correct behavior. It you expect the script to call gnutar, do not include the -o option as gnutar implements this option in a way that violates UNIX-98.

Star strips leading ./ sequences from pathnames. This lets star in many cases store longer pathnames than other implementations.

The POSIX.1-1988 method (ustar format) of storing files with pathnames that are longer than 100 chars has some limitations:

The name field (100 chars) an inserted slash (`/') and the prefix field (155 chars) produce the pathname of the file. When recreating the original filename, name and prefix are concatenated, using a slash character in the middle. If a pathname does not fit in the space provided or may not be split at a slash character so that the parts will fit into 100 + 155 chars, the file may not be archived. Linknames longer than 100 chars may not be archived too.

The star, xstar, xustar, exustar, pax, and gnutar archive formats don't have these limitations. While gnutar uses a method that makes it impossible for other tar implementations (except star) to restore filenames that are longer than 100 chars, the xstar, xustar, exustar and pax/epax archive format uses a method that allows an POSIX.1-1988 compliant way of storing filenames, if the POSIX method would allow this. When the archive format is xustar, exustar or pax/epax very long filenames are stored using extended headers from the POSIX.1-2001 standard.

Some buggy tar implementations will generate incorrect filenames during a restore operation if the archive contains pathnames or linknames of exactly 100 chars length.

Star adds a tar signature in the last four bytes of each tar header if the archive format is star or xstar. This is no problem with the star archive format as it is an extension of the old pre POSIX.1-1988 tar format. On the other side, the xstar archive format claims to be as POSIX.1-1988 compliant as possible. Inserting this tar signature is a minor deviation from the standard that has the last 12 bytes of each header reserved for future use. On the other side, tar implementations such as some pax implementations that only compute checksums on the first 500 bytes of the header are violating the standard that requests the checksum to be computed on all 512 bytes of the tar header. All tar implementations that are 100% Posix compliant will be able to extract xstar archives as long as no new standard is defined that claims the last 12 bytes of the header for a different use. But then the ustar version number should be changed from `00' to `01'. Now, that the POSIX-2001 standard has been accepted, it is even predictable that all extensions to the standard tar format will go into the POSIX.1-2001 extended headers which are extensible to include any feature without future limitation. The only known tar implementation that also uses the last 12 bytes of the tar header is Sun's tar which uses these 12 bytes for files that are split over several archives. Such archives created by Sun's tar are not readable by the buggy pax implementation too. The Sun extension is not incompatible to the star signature because Sun expects an octal number at the beginning of the 12 byte field which is a null character in the star case.

Star uses these four bytes since 1985 without problems. If you need a 100% POSIX.1-1988 and 100% POSIX.1-2001 compliant tar archive, you may use the xustar, exustar or the pax/epax archive format. The probability of falsely detecting other tar formats as xustar or exustar format however is higher.

There is no way to ask for the n-th occurrence of a file.

The way EOF is handled by star differs, whether the fifo is in effect or not. If the fifo is not used, star stops reading the archive if it encounters a logical EOF record in the archive. If the fifo is used, star may read until the fifo is full or until the real EOF mark on tape is reached. How much data star actually reads depends on the time when the star foreground process sends a fifo shutdown signal to the background fifo read process.

Gnu tar often creates tar archives with incorrect logical EOF marks. The standard requires two blocks that are completely zeroed, whereas gnutar often only adds one of them.

Old versions of tar found on SYSVr3 and earlier cannot read tar archives with a blocksize greater than 10 kBytes.

The method of storing sparse files currently used with the star and xstar format is not guaranteed to be used in later versions of star. If the author decides to change this method, later versions of star may not be able to restore sparse files from tar archives made by the current version of star.

Some tar implementations violate the standard in using only the first 500 Bytes of the header for checksum computation. These tar implementations will not accept star and xstar type tar archives.

Sun's Solaris 2.x tar implementation violates the Posix standard. Tar archives generated by star cause Sun's tar to print tar: impossible file type messages. You may ignore these messages.

Gnutar's dumpdirs are non standard and are currently not implemented.

If gnutar archives sparse files with more than four holes, it produces archives that violate the standard in a way that prevents other tar implementations to read these archives. Star knows about that and is able to handle these gnutar archives.

The filetype N (LF_NAMES) from gnutar (an obsolete method of storing long names) will never be implemented.

Note that on operating systems (like DOS) that do not implement real pipes, star implements compression via a temporary file. Using compression thus is limited by the maximum file size and the available disk space.

The extended file flags implementation (see -xfflags option) on Linux is buggy by design. In order to retrieve the needed information, every file needs to be opened. If the /dev directory is included in create mode, every possible driver will be loaded which may hang the system for a long time. In the worst case, unwanted side effects from opening devices (such as causing tape drives to rewind the media) may be caused.

SECURITY NOTES¶

If you unpack a tar archive in a non empty directory, any file in that directory may be overwritten unless you specify the -k option. If the archive contains symbolic links or hard links, star may even overwrite files outside the current directory. If the directory where the archive is been unpacked is not empty and contains contains symbolic links or hard links to directories outside that directory, star may also overwrite files outside the current directory. As many other commands, star usually has all possible permissions when run as root. Unpacking archives as root thus may have fatal results to any file on your system. Be very careful when you try to extract an archive that has not been created by you. It is possible to create hand crafted tar archives that may overwrite critical files (like /etc/passwd) on your system. In addition all tar archives that have been created with the list= option and tar archives where the C= option was not specified before all file type arguments may be critical.

A good advise is to extract all doubtful archives as non root in an empty directory and to neither specify the -/ nor -.. or -no-secure-links options. If you get a warning, you should unpack the archive a second time and specify the options -k, -w and -nowarn in addition to the options used for the first run.

See the ENVIRONMENT section and /etc/default/star for ways to configure the default behavior.

SUID NOTES¶

If star is installed suid root, star is able to make connections to remote archives for non root users. This is done by using the rcmd(3) interface to get a connection to a rmt(1) server.

Star resets its effective uid back to the real user id immediately after setting up the remote connection to the rmt server and before opening any other file.

If star has not been installed suid root and not called by root, it will try to create the remote connection via rsh(1) or ssh(1) (in case the environment RSH has been set to ssh). Note that in this case, the throughput to the remote tape server will be much lower than with a connection that has been initiated via rcmd(3).

LIMITATIONS¶

If star is running on a large file aware platform, star is able to handle files up to 8 GB in a mode that is compliant to the POSIX.1-1988 ustar format. With a nonstandard star specific extension, up to 95 bits may be used to code the filesize. This will handle files up to 200,000,000 TB. With the new POSIX.1-2001 extended headers used by the xustar, exustar and pax/epax format, any filesize may be archived.

BUGS¶

The fact that the -f option has to be implemented in a way that is compatible with old tar implementations gives several problems. The options -fifostats, -force-hole, -force-remove and -fifo interfere with the -f option and the fact that they exist prevents users from using filenames like e.g. ifo using the traditional way where the filename directly follows the string -f without any space between the option name and the file name. However, there is no problem to use a file named ifo by by calling -f ifo, f=ifo, -f=ifo or -f= ifo. Be careful not to make typos with the above options. The result could be that a file is created as a result of the mistyped option.

There is currently no way to set the fifo lowwater and highwater marks.

If you ever discover a hang in the fifo of star, get the process ids for both star processes, send both a RTMAX signal using kill(1) and report the diagnostic output.

There is currently no way to automatically delete files in the target file tree if they are obsolete. Star should implement something similar to gnutar's dumpdirs.

If not invoked by the super user star may not be able to extract files if they reside in read only directories.

Star is not able to make a complete backup of a filesystem if files are hidden by a mount that is in effect on a directory of this filesystem. This may be avoided in case of the ufs filesystem if the backup is made off a ufs snapshot (see the man page for fssnap(1m) It could be avoided for any filesystem if the loopback filesystem had an option that tells lofs not to traverse mountpoints.

For now (late 2002), we know that the following programs are broken and do not implement signal handling correctly:

rsh

on SunOS-5.0...SunOS-5.9

ssh

from ssh.com

ssh

from openssh.org

Sun already did accept a bug report for rsh(1)/ssh(1). Openssh.org accepted and fixed a bug for their implementation of ssh(1).

If you use star to create a remote connection via an unfixed rsh(1) or ssh(1), be prepared that terminal generated signals may interrupt the remote connection.

Mail other bugs and suggestions to schilytools@mlists.in-berlin.de or open a ticket at https://codeberg.org/schilytools/schilytools/issues.

The mailing list archive may be found at:

https://mlists.in-berlin.de/mailman/listinfo/schilytools-mlists.in-berlin.de.

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 replaced the tap program from First Edition Unix.

Star was first created in 1982 to extract tapes on a UNIX clone (UNOS) that had no tar command. In 1985 the first fully functional version has been released as mtar.

When the old star format extensions have been introduced in 1985, it was renamed to star (Schily tar). In 1994, Posix 1003.1-1988 extensions were added and star was renamed to star (Standard tar).

AUTHORS¶

Joerg Schilling and the schilytools project authors.

SOURCE DOWNLOAD¶

The source code for star is included in the schilytools project and may be retrieved from the schilytools project at Codeberg at

https://codeberg.org/schilytools/schilytools.

The download directory is

https://codeberg.org/schilytools/schilytools/releases.