2 <title>vac(1) - Plan 9 from User Space</title>
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9 <tr><td width=20><td><b>VAC(1)</b><td align=right><b>VAC(1)</b>
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12 <p><font size=+1><b>NAME </b></font><br>
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16 vac – create a vac archive on Venti<br>
19 <p><font size=+1><b>SYNOPSIS </b></font><br>
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23 <tt><font size=+1>vac</font></tt> [ <tt><font size=+1>−mqsv</font></tt> ] [ <tt><font size=+1>−b</font></tt> <i>blocksize</i> ] [ <tt><font size=+1>−d</font></tt> <i>oldvacfile</i> ] [ <tt><font size=+1>−e</font></tt> <i>exclude</i>
24 ] [ <tt><font size=+1>−f</font></tt> <i>vacfile</i> ] [ <tt><font size=+1>−i</font></tt> <i>name</i> ] [ <tt><font size=+1>−h</font></tt> <i>host</i> ] <i>file ...<br>
27 <p><font size=+1><b>DESCRIPTION </b></font><br>
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31 <i>Vac</i> creates an archival copy of Plan 9 file trees on Venti. It
32 can be used to build a simple backup system. One of the unusual
33 properties of Venti is that duplicate blocks are detected and
34 coalesced. When <i>vac</i> is used on a file tree that shares data with
35 an existing archive, the consumption of storage will be approximately
36 equal to an incremental backup. This reduction in storage consumption
37 occurs transparently to the user.
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40 As an optimization, the <tt><font size=+1>−d</font></tt> and <tt><font size=+1>−q</font></tt> options, described below, can
41 be used to explicitly create an archive relative to an existing
42 archive. These options do not change the resulting archive generated
43 by <i>vac</i>, but simply reduce the number of write operations to Venti.
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47 The output of <i>vac</i> is the hexadecimal representation of the Sha1
48 fingerprint of the root of the archive, in this format:<br>
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52 <tt><font size=+1>vac:64daefaecc4df4b5cb48a368b361ef56012a4f46<br>
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58 Option to <i>vac</i> are:<br>
59 <tt><font size=+1>−b</font></tt> <i>blocksize<br>
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63 Specifies the block size that data will be broken into. The units
64 for the size can be specified by appending <tt><font size=+1>k</font></tt> to indicate kilobytes.
65 The default is 8k. The size must be in the range of 512 bytes
69 <tt><font size=+1>−d</font></tt> <i>oldvacfile<br>
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73 Reduce the number of blocks written to Venti by comparing the
74 files to be stored with the contents of an existing <i>vac</i> file tree
75 given by <i>oldvacfile</i>.<br>
78 <tt><font size=+1>−e</font></tt> <i>exclude<br>
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82 Do not include the file or directory specified by <i>exclude</i>. This
83 option may be repeated multiple times.<br>
86 <tt><font size=+1>−f</font></tt> <i>vacfile<br>
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90 The results of <i>vac</i> are place in <i>vacfile</i>, or the standard output
91 if no file is given.<br>
94 <tt><font size=+1>−i</font></tt> <i>name<br>
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98 Include standard input as one of the input files, storing it in
99 the archive with the specified <i>name</i>.<br>
102 <tt><font size=+1>−h</font></tt> <i>host<br>
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106 The network address of the Venti server. The default is taken
107 from the environment variable <tt><font size=+1>venti</font></tt>.<br>
110 <tt><font size=+1>−m</font></tt> Expand and merge any <i>vac</i> archives that are found while reading
111 the input files. This option is useful for building an archive
112 from a collection of existing archives. Each archive is inserted
113 into the new archive as if it had been unpacked in the directory
114 in which it was found. Multiple archives can be unpacked in
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118 a single directory and the contents will be merged. To be detected,
119 the archives must end in <tt><font size=+1>.vac</font></tt>. Note, an archive is inserted by
120 simply copying the root fingerprint and does not require the archive
124 <tt><font size=+1>−q</font></tt> Increase the performance of the <tt><font size=+1>−d</font></tt> option by detecting unchanged
125 files based on a match of the files name and other meta data,
126 rather than examining the contents of the files.<br>
127 <tt><font size=+1>−s</font></tt> Print out various statistics on standard error.<br>
128 <tt><font size=+1>−v</font></tt> Produce more verbose output on standard error, including the
129 name of the files added to the archive and the vac archives that
130 are expanded and merged.<br>
133 <p><font size=+1><b>SOURCE </b></font><br>
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137 <tt><font size=+1>/usr/local/plan9/src/cmd/vac<br>
140 <p><font size=+1><b>SEE ALSO </b></font><br>
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144 Plan 9’s <i>vacfs</i>(4) and <i>venti</i>(8)<br>
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