vac man page on Plan9

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VAC(1)									VAC(1)

       vac, unvac - create, extract a vac archive on Venti

       vac  [  -mqsv  ] [ -b blocksize ] [ -d oldvacfile ] [ -e exclude ] [ -f
       vacfile ] [ -i name ] [ -h host ] file ...

       unvac [ -Tctv ] [ -h host ] vacfile [ file ...  ]

       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 con‐
       sumption 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  sim‐
       ply reduce the number of write operations to Venti.

       The output of vac is the hexadecimal representation of the SHA1 finger‐
       print of the root of the archive, in this format:


       The options to vac are:

       -b blocksize
	      Specifies the block size that data will  be  broken  into.   The
	      units  for  the  size  can be specified by appending to indicate
	      kilobytes.  The default is 8k.  The size must be in the range of
	      512 bytes to 52k.

       -d oldvacfile
	      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.

       -e exclude
	      Do not include the file or directory specified by exclude.  This
	      option may be repeated multiple times.

       -f vacfile
	      The results of vac are placed in vacfile, or the standard output
	      if no file is given.

       -i name
	      Include  standard input as one of the input files, storing it in
	      the archive with the specified name.

       -h host
	      The network address of the Venti server.	The default  is	 taken
	      from  the environment variable venti.  If this variable does not
	      exist, then the default is the metaname  $venti,	which  can  be
	      configured via ndb(6).

       -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 will be  merged.
	      To  be  detected,	 the  archives must end in Note, an archive is
	      inserted by simply copying the root  fingerprint	and  does  not
	      require the archive to be unpacked.

       -q     Increase the performance of the -d option by detecting unchanged
	      files based on a match of the files name and  other  meta	 data,
	      rather than examining the contents of the files.

       -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.

       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:

       -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

       -h     as per vac.

       -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.


       vacfs(4), venti(8)

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