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<h3><a href="../index.html">Table Of Contents</a></h3>
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<li class="toctree-l1"><a class="reference internal" href="../about.html">About S3QL</a></li>
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<li class="toctree-l1"><a class="reference internal" href="../installation.html">Installation</a></li>
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<li class="toctree-l1"><a class="reference internal" href="../backends.html">Storage Backends</a></li>
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<li class="toctree-l1"><a class="reference internal" href="../mkfs.html">File System Creation</a></li>
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<li class="toctree-l1"><a class="reference internal" href="../adm.html">Managing Buckets</a></li>
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<li class="toctree-l1"><a class="reference internal" href="../mount.html">Mounting</a></li>
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<li class="toctree-l1"><a class="reference internal" href="../special.html">Advanced S3QL Features</a></li>
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<li class="toctree-l1"><a class="reference internal" href="../umount.html">Unmounting</a></li>
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<li class="toctree-l1"><a class="reference internal" href="../fsck.html">Checking for Errors</a></li>
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<li class="toctree-l1"><a class="reference internal" href="../contrib.html">Contributed Programs</a></li>
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<li class="toctree-l1"><a class="reference internal" href="../tips.html">Tips & Tricks</a></li>
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<li class="toctree-l1"><a class="reference internal" href="../issues.html">Known Issues</a></li>
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<li class="toctree-l1 current"><a class="reference internal" href="index.html">Manpages</a><ul class="current">
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<li class="toctree-l2"><a class="reference internal" href="mkfs.html">The <strong class="program">mkfs.s3ql</strong> command</a></li>
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<li class="toctree-l2"><a class="reference internal" href="adm.html">The <strong class="program">s3qladm</strong> command</a></li>
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<li class="toctree-l2"><a class="reference internal" href="mount.html">The <strong class="program">mount.s3ql</strong> command</a></li>
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<li class="toctree-l2"><a class="reference internal" href="stat.html">The <strong class="program">s3qlstat</strong> command</a></li>
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<li class="toctree-l2"><a class="reference internal" href="ctrl.html">The <strong class="program">s3qlctrl</strong> command</a></li>
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<li class="toctree-l2 current"><a class="current reference internal" href="">The <strong class="program">s3qlcp</strong> command</a></li>
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<li class="toctree-l2"><a class="reference internal" href="rm.html">The <strong class="program">s3qlrm</strong> command</a></li>
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<li class="toctree-l2"><a class="reference internal" href="lock.html">The <strong class="program">s3qllock</strong> command</a></li>
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<li class="toctree-l2"><a class="reference internal" href="umount.html">The <strong class="program">umount.s3ql</strong> command</a></li>
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<li class="toctree-l2"><a class="reference internal" href="fsck.html">The <strong class="program">fsck.s3ql</strong> command</a></li>
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<li class="toctree-l2"><a class="reference internal" href="pcp.html">The <strong class="program">pcp</strong> command</a></li>
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<li class="toctree-l2"><a class="reference internal" href="expire_backups.html">The <strong class="program">expire_backups</strong> command</a></li>
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<li class="toctree-l1"><a class="reference internal" href="../resources.html">Further Resources / Getting Help</a></li>
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<div class="section" id="the-s3qlcp-command">
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<h1>The <strong class="program">s3qlcp</strong> command<a class="headerlink" href="#the-s3qlcp-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">s3qlcp </span><span class="ge">[options]</span><span class="l"> </span><span class="nv"><source-dir></span><span class="l"> </span><span class="nv"><dest-dir></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">s3qlcp</strong> command duplicates the directory tree <tt class="var docutils literal"><span class="pre">source-dir</span></tt>
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into <tt class="var docutils literal"><span class="pre">dest-dir</span></tt> without physically copying the file contents.
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Both source and destination must lie inside the same S3QL file system.</p>
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<p>The replication will not take any additional space. Only if one of
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directories is modified later on, the modified data will take
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additional storage space.</p>
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<p><tt class=" docutils literal"><span class="pre">s3qlcp</span></tt> can only be called by the user that mounted the file system
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and (if the file system was mounted with <tt class=" docutils literal"><span class="pre">--allow-other</span></tt> or <tt class=" docutils literal"><span class="pre">--allow-root</span></tt>)
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the root user. This limitation might be removed in the future (see <a class="reference external" href="http://code.google.com/p/s3ql/issues/detail?id=155">issue 155</a>).</p>
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<li>After the replication, both source and target directory will still
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be completely ordinary directories. You can regard <tt class=" docutils literal"><span class="pre"><src></span></tt> as a
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snapshot of <tt class=" docutils literal"><span class="pre"><target></span></tt> or vice versa. However, the most common
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usage of <tt class=" docutils literal"><span class="pre">s3qlcp</span></tt> is to regularly duplicate the same source
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directory, say <tt class=" docutils literal"><span class="pre">documents</span></tt>, to different target directories. For a
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e.g. monthly replication, the target directories would typically be
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named something like <tt class=" docutils literal"><span class="pre">documents_Januray</span></tt> for the replication in
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January, <tt class=" docutils literal"><span class="pre">documents_February</span></tt> for the replication in February etc.
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In this case it is clear that the target directories should be
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regarded as snapshots of the source directory.</li>
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<li>Exactly the same effect could be achieved by an ordinary copy
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program like <tt class=" docutils literal"><span class="pre">cp</span> <span class="pre">-a</span></tt>. However, this procedure would be orders of
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magnitude slower, because <tt class=" docutils literal"><span class="pre">cp</span></tt> would have to read every file
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completely (so that S3QL had to fetch all the data over the network
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from the backend) before writing them into the destination folder.</li>
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<li>Before starting with the replication, S3QL has to flush the local
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cache. So if you just copied lots of new data into the file system
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that has not yet been uploaded, replication will take longer than
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<div class="section" id="snapshotting-vs-hardlinking">
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<h3>Snapshotting vs Hardlinking<a class="headerlink" href="#snapshotting-vs-hardlinking" title="Permalink to this headline">¶</a></h3>
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<p>Snapshot support in S3QL is inspired by the hardlinking feature that
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is offered by programs like <a class="reference external" href="http://www.samba.org/rsync">rsync</a> or
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<a class="reference external" href="http://savannah.nongnu.org/projects/storebackup">storeBackup</a>.
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These programs can create a hardlink instead of copying a file if an
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identical file already exists in the backup. However, using hardlinks
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has two large disadvantages:</p>
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<li>backups and restores always have to be made with a special program
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that takes care of the hardlinking. The backup must not be touched
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by any other programs (they may make changes that inadvertently
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affect other hardlinked files)</li>
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<li>special care needs to be taken to handle files which are already
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hardlinked (the restore program needs to know that the hardlink was
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not just introduced by the backup program to safe space)</li>
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<p>S3QL snapshots do not have these problems, and they can be used with
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any backup program.</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">s3qlcp</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">--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">--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">--version</span></kbd></td>
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<td>just print program version and exit</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">s3qlcp</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>The S3QL homepage is at <a class="reference external" href="http://code.google.com/p/s3ql/">http://code.google.com/p/s3ql/</a>.</p>
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<p>The full S3QL documentation should also be installed somewhere on your
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system, conventional locations are <tt class="file docutils literal"><span class="pre">/usr/share/doc/s3ql</span></tt> or
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<tt class="file docutils literal"><span class="pre">/usr/local/doc/s3ql</span></tt>.</p>
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