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 NAME     
 |  |  |  | vac, unvac – create, extract a vac archive on Venti 
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 SYNOPSIS     
 |  |  |  | vac [ −mqsv ] [ −a vacfile ] [ −b blocksize ] [ −d oldvacfile
    ] [ −e exclude ] [ −f vacfile ] [ −i name ] [ −h host ] [ −x excludefile
    ] file ... 
    
    
    unvac [ −Tcdtv ] [ −h host ] vacfile [ file ... ] 
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 DESCRIPTION     
 |  |  |  | Vac creates an archival copy of Plan 9 file trees on Venti. It
    can be used to build a simple backup system. One of the unusual
    properties of Venti is that duplicate blocks are detected and
    coalesced. When vac is used on a file tree that shares data with
    an existing archive, the consumption of storage will be approximately
    equal to an incremental backup.
    This reduction in storage consumption occurs transparently to
    the user. 
    
    
    As an optimization, the −d and −q options, described below, can
    be used to explicitly create an archive relative to an existing
    archive. These options do not change the resulting archive generated
    by vac, but simply reduce the number of write operations to Venti.
    
    
    
    The output of vac is the hexadecimal representation of the SHA1
    fingerprint of the root of the archive, in this format: 
 The options are:|  |  |  | vac:64daefaecc4df4b5cb48a368b361ef56012a4f46 
 | 
 −a vacfile
 
 −b blocksize|  |  |  | Specifies that vac should create or update a backup archive, inserting
        the files under an extra two levels of directory hierarchy named
        yyyy/mmdd (year, month, day) in the style of the dump file system
        (see Plan 9’s fs(4)). If vacfile already exists, an additional
        backup day is added to the existing hierarchy, behaving as though
        the −d flag was
        specified giving the most recent backup tree in the archive. Typically,
        this option is used as part of a nightly backup script. This option
        cannot be used with −d or −f. 
 | 
 
 −d oldvacfile|  |  |  | Specifies the block size that data will be broken into. The units
        for the size can be specified by appending k to indicate kilobytes.
        The default is 8k. The size must be in the range of 512 bytes
        to 52k. 
 | 
 
 −e exclude|  |  |  | Reduce the number of blocks written to Venti by comparing the
        files to be stored with the contents of an existing vac file tree
        whose score is stored in oldvacfile. 
 | 
 
 −f vacfile|  |  |  | Do not include the file or directory specified by exclude. This
        option may be repeated multiple times. Exclude can be a shell
        pattern as accepted by rc(1), with one extension: ... matches
        any sequence of characters including slashes. 
 | 
 
 −i name|  |  |  | The results of vac are placed in vacfile, or the standard output
        if no file is given. 
 | 
 
 −h host|  |  |  | Include standard input as one of the input files, storing it in
        the archive with the specified name. 
 | 
 
 −m    Expand and merge any vac archives that are found while reading
    the input files. This option is useful for building an archive
    from a collection of existing archives. Each archive is inserted
    into the new archive as if it had been unpacked in the directory
    in which it was found. Multiple archives can be unpacked in a
    single directory and the contents|  |  |  | The network address of the Venti server. The default is taken
        from the environment variable venti. 
 | 
 −q    Increase the performance of the −a or −d options by detecting
    unchanged files based on a match of the files name and other meta
    data, rather than examining the contents of the files.|  |  |  | will be merged. To be detected, the archives must end in .vac.
        Note, an archive is inserted by simply copying the root fingerprint
        and does not require the archive to be unpacked. 
 | 
 −s    Print out various statistics on standard error.
 −v    Produce more verbose output on standard error, including the
    name of the files added to the archive and the vac archives that
    are expanded and merged.
 −x excfile
 
 Unvac lists or extracts files stored in the vac archive vacfile,
    which can be either a vac archive string in the format given above
    or the name of a file containing one. If file arguments are given,
    only those files or directories will be extracted. The options
    are:|  |  |  | Read exclude patterns from the file excfile. Blank lines and lines
        beginning with # are ignored. All other lines should be of the
        form include pattern or exclude pattern . When considering whether
        to include a directory or file in the vac archive, the earliest
        matching pattern in the file applies. The patterns are the same
        syntax accepted by the
        −e option. This option may be repeated multiple times. | 
 −T    Set the modification time on extracted files to the time listed
    in the archive.
 −c    Write extracted files to standard output instead of creating
    a file.
 −d    Reduce the number of blocks read from Venti by comparing the
    files to be stored with their counterparts in the file system.
    This option cannot be used with −c.
 −t    Print a list of the files to standard output rather than extracting
    them.
 −v    If extracting files, print the name of each file and directory
    to standard error. If listing files, print metadata in addition
    to the names.
 
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 SOURCE     
 SEE ALSO     
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