STAR(1)

NAME
star - unique standard tape archiver

SYNOPSIS
star command [ options ] file1 ... filen
ustar command [ options ] file1 ... filen
tar command [ options ] file1 ... filen

DESCRIPTION
Star is a very fast tar(1) like tape archiver with improved functionality.

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.

FEATURES
Star includes the first free implementation of POSIX.1-2001 extended tar headers. The 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 fetch files from a list of directories (in create mode) or to distribute files to a list of directories (in extract mode).

Star includes a sophisticated diff command. 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 (1023 bytes with old OS versions and 4095 bytes with POSIX.1-2001) may be archived. Later versions may be able to deal with longer pathnames.

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, 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 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 automatically recognizes and handles compressed archives inside plain files.

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

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 compatibilitx 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.

-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 and gives with a good choice of diffopts - in some cases - a more readable output than diff -r. See diffopts for more details.

-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 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.

-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.

Exactly one of the commands above must be specified.

If one or more pattern are specified, they apply to any of the command listed above.

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.

-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.

-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:

        remove 'filename' ? Y(es)/N(o) :

-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 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.

-block-number
    Print the archive block number (archive offset / 512) at the beginning of each line when in verbose mode. This allows 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.

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 posible 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, 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:

        star: Blocksize = # records.

    Where # is the blocking factor in multiples of 512 bytes. The blocks= option and the bs= option are equivalent methods to specify the tape block size. The blocks= option is preferred by people who like to use an option that behaves similar to the interface of the historic tar(1) implementations.

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).

-bz run the input or output through a bzip2 pipe - see option -z below. As both the -bz and the -z option are non standard, it makes sense to omit the -bz and the -z inside shell scripts if you are going to extract a compressed archive that is located inside a plain file as star will auto detect compression and choose the right decompression option to extract.

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.

    •   In list mode (with the -t flag), star ignores all -C options.

    •   In create mode (with the -c, -r and -u flag), star walks through all -C options and file type arguments. While a BSD derived tar(1) implementation goes back to the current working directory after storing one file argument that immediately follows the -C option, star changes the directory only if a new -C option follows. To emulate the behavior of a BSD derived tar(1), add a -C . option after the file argument.

    •   In extract mode (with the -x, -n and -diff flag), star builds a pattern list together with corresponding directories and performs a chdir(2) to the corresponding directory of a matching pattern. All pat= options in this case are interpreted as if they were preceded by a -C . option. See EXAMPLES for more information.

-copylinks
    This option allows to copy hard/symlinks 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.

-ctime
    If used with the list command, this lists ctime rather than mtime if the archive format is star, xstar, xustar, exustar, or pax. If used with the extract command and the same archive formats, this tries 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. 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.

-D  Do not descend directories. 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.

-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:

    help
        Print a summary of possible members of the diffopts list.

    !

    not Invert the meaning of all members in the diffopts list i.e. exclude all present options from an initially complete set compare list. When using csh(1) you might have problems to use ! due to its strange parser. This is why the not alias exists.

    perm
        Compare file permissions. With this option in effect, star compares the low order 12 bits of the st_mode field.

    mode
        Same as perm.

    type
        Compare file type. Note that star cannot compare the file type in case of a hard link.

    nlink
        Compare link count on hardlinks (currently not supported).

    uid Compare numerical user id of file.

    gid Compare numerical group id of file.

    uname
        Compare ASCII version of user id of file. The user name is mapped via the file /etc/passwd.

    gname
        Compare ASCII version of group id of file. The group name is mapped via the file /etc/group.

    id  Compare all user/group related info of file. Note that this will always find differences if the source and target system use different user or group mappings.

    size
        Compare file size. Note that star cannot compare the file size in case of a hard link.

    nlink
        Compare link count on hardlinks (currently not supported).

    data
        Compare content of file. If star already found that the size of the files differ, it will not compare the content anymore.

    cont
        Same as data.

    rdev
        Compare major/minor numbers for device nodes.

    hardlink
        Compare target of hardlinks.

    symlink
        Compare target of symlinks. This evaluates the value returned by the readlink(2) call.

    atime
        Compare access time of file. This only works with if the archive format is star, xstar, xustar, exustar, or pax.

    mtime
        Compare modification time of file.

    ctime
        This only works with if the archive format is star, xstar, xustar, exustar, or pax.

    times
        Shorthand for: atime,mtime,ctime.

    If optlst starts with a ! the meaning of all members in optlst is inverted as with the not optlist member.

    If diffopts are not specified, star compares everything but the access time of the files.

-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.

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

-dump
    This currently is an experimental option to make it easier to implement a star version that supports true incremental dumps. Star currently sets the archive type to exustar and archives more inode meta data inside POSIX.1-2001 extended headers.

-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.

-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 dumb 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 that gives 12MB/s transfer rate, a fifo of 256 MB size will keep the tape at least streaming in units of 20 seconds. 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 privilleges. 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 to send 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.

-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. 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.

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.

H=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:

    help
        Print a help message about possible header types.

    tar Old UNIX tar format. This archive format may only store plain files, directories and symbolic links. Pathnames or linknames longer than 99 chars may not be archived. See also the -d option as a note to some even older tar implementations.

        If the tar format has been selected, star will not use enhancements to the historic tar format. File size is limited to 2 GB - 2 bytes, uid/gid is limited to 262143. Sparse files will be filled up with zeroes.

    star
        Old star standard format. This is an upward/downward compatible enhancement of the old (pre Posix) UNIX tar format. It has been introduced in 1985 and therefore is not Posix compliant. The star format allows to archive special files (even sockets) and records access time and creation time besides the modification time. Newer versions of the old star format allow very long filenames (100+155 chars and above), linknames > 100 chars and sparse files. This format is able to copy the device nodes on HP-UX that have 24 bits in the minor device number, which is more then the 21 bits that are possible with the POSIX-1003.1-1988 archive format.

    gnutar
        This is a commonly used, but unfortunately not Posix compliant (although designed after 1987) enhancement to the old tar format. Do not use the gnutar archive format unless you want to create an archive for a target system that is known to have only the gnutar program available. The gnutar archive format violates basic rules for any (even the historic) tar archive format. Using the gnutar archive format causes a high risk that the resulting archive may only be read by gnutar or by star. The implementation of the gnutar archive format within star is not complete, but sufficient for most gnutar archives. See NOTES for more information.

    ustar
        IEEE/Posix1003/IEC-9945-1-1988 Standard Data Interchange format. With this option in effect, star will generate 100% POSIX.1-1988 compliant tar archives. Files with pathnames longer than 100+155 chars or linknames longer than 100 chars may not be archived. If star is called as ustar the default archive format is ustar.

        If the ustar format has been selected, star will not use enhancements to the POSIX.1-1988 tar format, the archive will be strictly conforming. File size is limited to 8 GB, uid/gid/major/minor is limited to 2097151. Sparse files will be filled up with zeroes.

    pax The IEEE/Posix1003/IEC-9945-1-1988 successor, the POSIX-1003.1-2001 Standard Data Interchange format.

        If the pax format has been selected, star will not use enhancements to the POSIX.1-2001 tar format, the archive will be strictly conforming. File size is unlimited, uid/gid/uname/gidname is unlimited, major/minor is limited to 2097151. Sparse files will be filled up with zeroes.

    xstar
        Extended standard tar format. Star uses the xstar format as default archive format. This is an upward/downward compatible enhancement of the IEEE/Posix1003/IEC-9945-1 Standard Data Interchange format. It allows among others very long filenames (100+130 chars and above) and records access time and creation time. The xstar format is the default format when star is neither called as tar nor called as ustar.

    xustar
        New format introduced 1998, that omits the tar signature at the end of the tar header. It is otherwise identical to the xstar format. As some tar implementations do not follow the POSIX rules and compute the checksum for less than 512 bytes of the tar header, this format may help to avoid problems with these tar implementations. The main other difference to the xstar format is that the format uses POSIX.1-2001 extended headers to overcome limitations of the historic tar format while the xstar format uses proprietary extensions. The xustar format is the default format when star is called as tar.

        File size is unlimited, uid/gid/uname/gidname is unlimited, major/minor is unlimited. Sparse files will be archived correctly.

    exustar
        A format similar to the xustar format but with forced POSIX.1-2001 extended headers. If this format is used together with the -acl option, star records Access Control Lists (ACLs) in POSIX.1-2001 extended headers.

        File size is unlimited, uid/gid/uname/gidname is unlimited, major/minor is unlimited. Sparse files will be archived correctly.

    suntar
        The extended header format found on Solaris 7/8. This format is similar to the pax format but does not handle atime and ctime and in addition uses 'X' as the typeflag for the extended headers instead of the standard 'x'.

        File size is unlimited, uid/gid/uname/gidname is unlimited, major/minor is unlimited. Sparse files will be filled up with zeroes.

    All tar archive formats may be interchanged if the archive contains no files that may not be archived by using the old tar format. Archives in the xstar format may be extracted by any 100% POSIX compliant tar implementation if they contain no files with pathnames > 100+130 chars and if they contain no sparse files that have been archived by using the -sparse option.

-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 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.

-I  Obsolete option, otherwise identical to -w.

-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.

-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.

-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.

    Note that not all filesystem allow to create 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 command from filename. The file filename must contain a list of filenames, each on a separate line. This option implies the -D option. To force star to descend directories, use the -dodesc option in this case.

-M  Do not descend mount points. This is useful when doing backups of complete filesystems. See NOTES for more information.

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

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
    This currently is an experimental option. In create mode, it causes star to archive all meta data of the file (e.g. uid, permissions, ...) bit 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 in future star versions that 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.

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 if in multi volume mode. If this option is not in effect, star will ask the user to confirm the volume change.

-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.

-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.)

-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_statistics
    obsoleted by -no-statistics

-no-statistics
    Do not print statistic messages at the end of a star run.

-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.

-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 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 -singed-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 superseeded 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.

-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 filemodes of directories. Without this option directories are created using the present umask(2). 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 will be able to restore the correct times of directories. 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.

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. 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 to restore 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. 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.

-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.

-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 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.

-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.

-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, pax, or suntar. 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. 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 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.

-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 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. 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. Files that do not fit on a single tape may not be stored with the current version of star.

-U  Restore files unconditionally. By default, an older file from the archive will not replace a corresponding newer file 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:

        get/put ? Y(es)/N(o)/C(hange name) :

    You may answer either `N' for No or <Return> to skip this file. If you answer `Y' the file is extracted or archived on tape with its original name. If you answer `C', you are prompted for a new name. This name is used for the filename on disk if star is in extract mode or for the archive name if star is in create mode.

-wready
    This option is 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. Star waits up to one minute for the drive to become ready if this option is specified.

-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.

-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.

-z  run the input or output through a gzip pipe. This is currently a quick and dirty hack, that mainly will cover the most common usage to compress the tar output if it is a file. No reblocking will be done, so this option will currently only make sense on plain files. The environment variable As both the -bz and the -z option are non standard, it makes sense to omit the -bz and the -z inside shell scripts if you are going to extract a compressed archive that is located inside a plain file as star will auto detect compression and choose the right decompression option to extract. STAR_COMPRESS_FLAG may be used to specify one option for gzip. If you want to write write compressed archives to tape, you should use
    star -c . | gzip | sdd ibs=4k obs=32k -fill of=/dev/rmt/1bn
    or
    star -c . | gzip | sdd ibs=4k obs=32k -fill ovsize=60m of=/dev/rmt/1bn
    if the tape can hold 60 MB.

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
    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.

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

To copy a file tree including the Access Control List entries for all files use:

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

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 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

ENVIRONMENT

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

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.

FILES
Currently none except the files implied be the command line from star.

In future, star may use /etc/default/star to set up global defaults.

SEE ALSO
tar(1), cpio(1), rcp(1), mt(1), rmt(1), match(1), dd(1), sdd(1), star(4/5), rcmd(3), fssnap(1m)

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 POSIX command line syntax for the tar command 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 to either write options separately or combined (in case of boolean flags), the POSIX 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 to specify a command line syntax as documented for the POSIX 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 POSIX 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 POSIX.

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 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 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 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.

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.

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 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.

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.

HISTORY
Star was first created in 1982 to extract tapes on a UNIX clone 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).

AUTHOR
Joerg Schilling
Seestr. 110
D-13353 Berlin
Germany

Mail bugs and suggestions to:

schilling@fokus.gmd.de or js@cs.tu-berlin.de or joerg@schily.isdn.cs.tu-berlin.de