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<li class="toctree-l2 current"><a class="current reference internal" href="">The <strong class="program">expire_backups</strong> command</a></li>
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<div class="section" id="the-expire-backups-command">
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<h1>The <strong class="program">expire_backups</strong> command<a class="headerlink" href="#the-expire-backups-command" title="Permalink to this headline">¶</a></h1>
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<div class="section" id="synopsis">
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<h2>Synopsis<a class="headerlink" href="#synopsis" title="Permalink to this headline">¶</a></h2>
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<div class="highlight-commandline"><div class="highlight"><pre><span class="l">expire_backups </span><span class="ge">[options]</span><span class="l"> </span><span class="nv"><age></span><span class="l"> </span><span class="ge">[<age> ...]</span><span class="l"></span>
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<div class="section" id="description">
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<h2>Description<a class="headerlink" href="#description" title="Permalink to this headline">¶</a></h2>
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<p>The <strong class="command">expire_backups</strong> command intelligently remove old backups that are no
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<p>To define what backups you want to keep for how long, you define a
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number of <em>age ranges</em>. <strong class="program">expire_backups</strong> ensures that you
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will have at least one backup in each age range at all times. It will
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keep exactly as many backups as are required for that and delete any
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backups that become redundant.</p>
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<p>Age ranges are specified by giving a list of range boundaries in terms
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of backup cycles. Every time you create a new backup, the existing
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backups age by one cycle.</p>
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<p>Example: when <strong class="program">expire_backups</strong> is called with the age range
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definition <tt class="docutils literal"><span class="pre">1</span> <span class="pre">3</span> <span class="pre">7</span> <span class="pre">14</span> <span class="pre">31</span></tt>, it will guarantee that you always have the
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following backups available:</p>
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<ol class="arabic simple">
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<li>A backup that is 0 to 1 cycles old (i.e, the most recent backup)</li>
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<li>A backup that is 1 to 3 cycles old</li>
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<li>A backup that is 3 to 7 cycles old</li>
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<li>A backup that is 7 to 14 cycles old</li>
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<li>A backup that is 14 to 31 cycles old</li>
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<div class="admonition note">
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<p class="first admonition-title">Note</p>
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<p class="last">If you do backups in fixed intervals, then one cycle will be
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equivalent to the backup interval. The advantage of specifying the
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age ranges in terms of backup cycles rather than days or weeks is
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that it allows you to gracefully handle irregular backup intervals.
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Imagine that for some reason you do not turn on your computer for
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one month. Now all your backups are at least a month old, and if you
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had specified the above backup strategy in terms of absolute ages,
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they would all be deleted! Specifying age ranges in terms of backup
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cycles avoids these sort of problems.</p>
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<p><strong class="program">expire_backups</strong> usage is simple. It requires backups to have
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names of the forms <tt class="docutils literal"><span class="pre">year-month-day_hour:minute:seconds</span></tt>
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(<tt class="docutils literal"><span class="pre">YYYY-MM-DD_HH:mm:ss</span></tt>) and works on all backups in the current
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directory. So for the above backup strategy, the correct invocation
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<div class="highlight-commandline"><div class="highlight"><pre><span class="l">expire_backups.py 1 3 7 14 31</span>
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<p>When storing your backups on an S3QL file system, you probably want to
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specify the <tt class="docutils literal"><span class="pre">--use-s3qlrm</span></tt> option as well. This tells
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<strong class="program">expire_backups</strong> to use the <a class="reference internal" href="../special.html#s3qlrm"><em>s3qlrm</em></a> command to
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delete directories.</p>
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<p><strong class="program">expire_backups</strong> uses a “state file” to keep track which
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backups are how many cycles old (since this cannot be inferred from
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the dates contained in the directory names). The standard name for
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this state file is <tt class="file docutils literal"><span class="pre">.expire_backups.dat</span></tt>. If this file gets
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damaged or deleted, <strong class="program">expire_backups</strong> no longer knows the ages
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of the backups and refuses to work. In this case you can use the
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<tt class="cmdopt docutils literal"><span class="pre">--reconstruct-state</span></tt> option to try to reconstruct the state
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from the backup dates. However, the accuracy of this reconstruction
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depends strongly on how rigorous you have been with making backups (it
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is only completely correct if the time between subsequent backups has
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always been exactly the same), so it’s generally a good idea not to
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tamper with the state file.</p>
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<div class="section" id="options">
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<h2>Options<a class="headerlink" href="#options" title="Permalink to this headline">¶</a></h2>
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<p>The <strong class="command">expire_backups</strong> command accepts the following options:</p>
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<div><table class="docutils option-list" frame="void" rules="none">
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<col class="option" />
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<col class="description" />
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<tr><td class="option-group">
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<kbd><span class="option">--quiet</span></kbd></td>
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<td>be really quiet</td></tr>
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<tr><td class="option-group">
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<kbd><span class="option">--debug</span></kbd></td>
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<td>activate debugging output</td></tr>
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<tr><td class="option-group">
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<kbd><span class="option">--version</span></kbd></td>
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<td>just print program version and exit</td></tr>
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<tr><td class="option-group">
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<kbd><span class="option">--state <var><file></var></span></kbd></td>
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<td>File to save state information in (default:
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”.expire_backups.dat”)</td></tr>
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<tr><td class="option-group">
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<kbd><span class="option">-n</span></kbd></td>
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<td>Dry run. Just show which backups would be deleted.</td></tr>
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<tr><td class="option-group" colspan="2">
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<kbd><span class="option">--reconstruct-state</span></kbd></td>
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<tr><td> </td><td>Try to reconstruct a missing state file from backup
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<tr><td class="option-group">
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<kbd><span class="option">--use-s3qlrm</span></kbd></td>
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<td>Use <tt class=" docutils literal"><span class="pre">s3qlrm</span></tt> command to delete backups.</td></tr>
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<div class="section" id="exit-status">
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<h2>Exit Status<a class="headerlink" href="#exit-status" title="Permalink to this headline">¶</a></h2>
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<p><strong class="command">expire_backups</strong> returns exit code 0 if the operation succeeded and 1 if some
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<div class="section" id="see-also">
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<h2>See Also<a class="headerlink" href="#see-also" title="Permalink to this headline">¶</a></h2>
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<p><strong class="command">expire_backups</strong> is shipped as part of S3QL, <a class="reference external" href="http://code.google.com/p/s3ql/">http://code.google.com/p/s3ql/</a>.</p>
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