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<li class="toctree-l1"><a class="reference internal" href="about.html">About S3QL</a></li>
<li class="toctree-l1"><a class="reference internal" href="installation.html">Installation</a></li>
<li class="toctree-l1"><a class="reference internal" href="backends.html">Storage Backends</a></li>
<li class="toctree-l1"><a class="reference internal" href="durability.html">Important Rules to Avoid Losing Data</a></li>
<li class="toctree-l1"><a class="reference internal" href="mkfs.html">File System Creation</a></li>
<li class="toctree-l1"><a class="reference internal" href="adm.html">Managing File Systems</a></li>
<li class="toctree-l1 current"><a class="current reference internal" href="">Mounting</a><ul>
<li class="toctree-l2"><a class="reference internal" href="#compression-algorithms">Compression Algorithms</a></li>
<li class="toctree-l2"><a class="reference internal" href="#notes-about-caching">Notes about Caching</a></li>
<li class="toctree-l2"><a class="reference internal" href="#automatic-mounting">Automatic Mounting</a></li>
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<li class="toctree-l1"><a class="reference internal" href="special.html">Advanced S3QL Features</a></li>
<li class="toctree-l1"><a class="reference internal" href="umount.html">Unmounting</a></li>
<li class="toctree-l1"><a class="reference internal" href="fsck.html">Checking for Errors</a></li>
<li class="toctree-l1"><a class="reference internal" href="authinfo.html">Storing Authentication Information</a></li>
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<div class="section" id="mounting">
<h1>Mounting<a class="headerlink" href="#mounting" title="Permalink to this headline">¶</a></h1>
<p>A S3QL file system is mounted with the <tt class="docutils literal"><span class="pre">mount.s3ql</span></tt> command. It has
the following syntax:</p>
<div class="highlight-commandline"><div class="highlight"><pre><span class="l">mount.s3ql </span><span class="ge">[options]</span><span class="l"> </span><span class="nv"><storage url></span><span class="l"> </span><span class="nv"><mountpoint></span><span class="l"></span>
</pre></div>
</div>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">S3QL is not a network file system like <a class="reference external" href="http://en.wikipedia.org/wiki/Network_File_System_%28protocol%29">NFS</a>
or <a class="reference external" href="http://en.wikipedia.org/wiki/CIFS">CIFS</a>. It can only be
mounted on one computer at a time.</p>
</div>
<p>This command accepts the following options:</p>
<blockquote>
<div><table class="docutils option-list" frame="void" rules="none">
<col class="option" />
<col class="description" />
<tbody valign="top">
<tr><td class="option-group">
<kbd><span class="option">--log <var><target></var></span></kbd></td>
<td>Write logging info into this file. File will be
rotated when it reaches 1 MiB, and at most 5 old log
files will be kept. Specify <tt class="docutils literal"><span class="pre">none</span></tt> to disable
logging. Default: <tt class="docutils literal"><span class="pre">~/.s3ql/mount.log</span></tt></td></tr>
<tr><td class="option-group" colspan="2">
<kbd><span class="option">--cachedir <var><path></var></span></kbd></td>
</tr>
<tr><td> </td><td>Store cached data in this directory (default:
<tt class="docutils literal"><span class="pre">~/.s3ql)</span></tt> (default: /home/nikratio/.s3ql)</td></tr>
<tr><td class="option-group" colspan="2">
<kbd><span class="option">--authfile <var><path></var></span></kbd></td>
</tr>
<tr><td> </td><td>Read authentication credentials from this file
(default: <tt class="docutils literal"><span class="pre">~/.s3ql/authinfo2)</span></tt> (default:
/home/nikratio/.s3ql/authinfo2)</td></tr>
<tr><td class="option-group" colspan="2">
<kbd><span class="option">--debug <var><module></var></span></kbd></td>
</tr>
<tr><td> </td><td>activate debugging output from <module>. Use <tt class="docutils literal"><span class="pre">all</span></tt> to
get debug messages from all modules. This option can
be specified multiple times. (default: None)</td></tr>
<tr><td class="option-group">
<kbd><span class="option">--quiet</span></kbd></td>
<td>be really quiet (default: False)</td></tr>
<tr><td class="option-group">
<kbd><span class="option">--ssl</span></kbd></td>
<td>Always use SSL connections when connecting to remote
servers. For backends that allow only encrypted
connections, S3QL uses SSL automatically, even if this
option is not set. (default: False)</td></tr>
<tr><td class="option-group">
<kbd><span class="option">--version</span></kbd></td>
<td>just print program version and exit</td></tr>
<tr><td class="option-group" colspan="2">
<kbd><span class="option">--cachesize <var><size></var></span></kbd></td>
</tr>
<tr><td> </td><td>Cache size in KiB (default: 102400 (100 MiB)). Should
be at least 10 times the maximum object size of the
filesystem, otherwise an object may be retrieved and
written several times during a single write() or
read() operation. (default: 102400)</td></tr>
<tr><td class="option-group" colspan="2">
<kbd><span class="option">--max-cache-entries <var><num></var></span></kbd></td>
</tr>
<tr><td> </td><td>Maximum number of entries in cache (default: 768).
Each cache entry requires one file descriptor, so if
you increase this number you have to make sure that
your process file descriptor limit (as set with
<tt class="docutils literal"><span class="pre">ulimit</span> <span class="pre">-n</span></tt>) is high enough (at least the number of
cache entries + 100).</td></tr>
<tr><td class="option-group">
<kbd><span class="option">--allow-other</span></kbd></td>
<td>Normally, only the user who called <tt class="docutils literal"><span class="pre">mount.s3ql</span></tt> can
access the mount point. This user then also has full
access to it, independent of individual file
permissions. If the <tt class="docutils literal"><span class="pre">--allow-other</span></tt> option is
specified, other users can access the mount point as
well and individual file permissions are taken into
account for all users. (default: False)</td></tr>
<tr><td class="option-group">
<kbd><span class="option">--allow-root</span></kbd></td>
<td>Like <tt class="docutils literal"><span class="pre">--allow-other</span></tt>, but restrict access to the
mounting user and the root user. (default: False)</td></tr>
<tr><td class="option-group">
<kbd><span class="option">--fg</span></kbd></td>
<td>Do not daemonize, stay in foreground (default: False)</td></tr>
<tr><td class="option-group">
<kbd><span class="option">--single</span></kbd></td>
<td>Run in single threaded mode. If you don’t understand
this, then you don’t need it. (default: False)</td></tr>
<tr><td class="option-group">
<kbd><span class="option">--upstart</span></kbd></td>
<td>Stay in foreground and raise SIGSTOP once mountpoint
is up. (default: False)</td></tr>
<tr><td class="option-group">
<kbd><span class="option">--profile</span></kbd></td>
<td>Create profiling information. If you don’t understand
this, then you don’t need it. (default: False)</td></tr>
<tr><td class="option-group" colspan="2">
<kbd><span class="option">--compress <var><name></var></span></kbd></td>
</tr>
<tr><td> </td><td>Compression algorithm to use when storing new data.
Allowed values: <tt class="docutils literal"><span class="pre">lzma</span></tt>, <tt class="docutils literal"><span class="pre">bzip2</span></tt>, <tt class="docutils literal"><span class="pre">zlib</span></tt>, none.
(default: <tt class="docutils literal"><span class="pre">lzma</span></tt>)</td></tr>
<tr><td class="option-group" colspan="2">
<kbd><span class="option">--metadata-upload-interval <var><seconds></var></span></kbd></td>
</tr>
<tr><td> </td><td>Interval in seconds between complete metadata uploads.
Set to 0 to disable. Default: 24h. (default: 86400)</td></tr>
<tr><td class="option-group">
<kbd><span class="option">--threads <var><no></var></span></kbd></td>
<td>Number of parallel upload threads to use (default:
auto). (default: None)</td></tr>
<tr><td class="option-group">
<kbd><span class="option">--nfs</span></kbd></td>
<td>Enable some optimizations for exporting the file
system over NFS. (default: False)</td></tr>
</tbody>
</table>
</div></blockquote>
<div class="section" id="compression-algorithms">
<h2>Compression Algorithms<a class="headerlink" href="#compression-algorithms" title="Permalink to this headline">¶</a></h2>
<p>S3QL supports three compression algorithms, LZMA, Bzip2 and zlib (with
LZMA being the default). The compression algorithm can be specified
freely whenever the file system is mounted, since it affects only the
compression of new data blocks.</p>
<p>Roughly speaking, LZMA is slower but achieves better compression
ratios than Bzip2, while Bzip2 in turn is slower but achieves better
compression ratios than zlib.</p>
<p>For maximum file system performance, the best algorithm therefore
depends on your network connection speed: the compression algorithm
should be fast enough to saturate your network connection.</p>
<p>To find the optimal algorithm and number of parallel compression
threads for your system, S3QL ships with a program called
<tt class="docutils literal"><span class="pre">benchmark.py</span></tt> in the <tt class="docutils literal"><span class="pre">contrib</span></tt> directory. You should run this program
on a file that has a size that is roughly equal to the block size of
your file system and has similar contents. It will then determine the
compression speeds for the different algorithms and the upload speeds
for the specified backend and recommend the best algorithm that is
fast enough to saturate your network connection.</p>
<p>Obviously you should make sure that there is little other system load
when you run <tt class="docutils literal"><span class="pre">benchmark.py</span></tt> (i.e., don’t compile software or encode
videos at the same time).</p>
</div>
<div class="section" id="notes-about-caching">
<h2>Notes about Caching<a class="headerlink" href="#notes-about-caching" title="Permalink to this headline">¶</a></h2>
<p>S3QL maintains a local cache of the file system data to speed up
access. The cache is block based, so it is possible that only parts of
a file are in the cache.</p>
<div class="section" id="maximum-number-of-cache-entries">
<h3>Maximum Number of Cache Entries<a class="headerlink" href="#maximum-number-of-cache-entries" title="Permalink to this headline">¶</a></h3>
<p>The maximum size of the cache can be configured with the <tt class="docutils literal"><span class="pre">--cachesize</span></tt>
option. In addition to that, the maximum number of objects in the
cache is limited by the <tt class="docutils literal"><span class="pre">--max-cache-entries</span></tt> option, so it is
possible that the cache does not grow up to the maximum cache size
because the maximum number of cache elements has been reached. The
reason for this limit is that each cache entry requires one open
file descriptor, and Linux distributions usually limit the total
number of file descriptors per process to about a thousand.</p>
<p>If you specify a value for <tt class="docutils literal"><span class="pre">--max-cache-entries</span></tt>, you should therefore
make sure to also configure your system to increase the maximum number
of open file handles. This can be done temporarily with the <tt class="docutils literal"><span class="pre">umask</span> <span class="pre">-n</span></tt>
command. The method to permanently change this limit system-wide
depends on your distribution.</p>
</div>
<div class="section" id="cache-flushing-and-expiration">
<h3>Cache Flushing and Expiration<a class="headerlink" href="#cache-flushing-and-expiration" title="Permalink to this headline">¶</a></h3>
<p>S3QL flushes changed blocks in the cache to the backend whenever a block
has not been accessed for at least 10 seconds. Note that when a block is
flushed, it still remains in the cache.</p>
<p>Cache expiration (i.e., removal of blocks from the cache) is only done
when the maximum cache size is reached. S3QL always expires the least
recently used blocks first.</p>
</div>
</div>
<div class="section" id="automatic-mounting">
<h2>Automatic Mounting<a class="headerlink" href="#automatic-mounting" title="Permalink to this headline">¶</a></h2>
<p>If you want to mount and umount an S3QL file system automatically at
system startup and shutdown, you should do so with one dedicated S3QL
init script for each S3QL file system.</p>
<p>If your system is using upstart, an appropriate job can be defined
as follows (and should be placed in <tt class="docutils literal"><span class="pre">/etc/init/</span></tt>):</p>
<div class="highlight-commandline"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre> 1
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41</pre></div></td><td class="code"><div class="highlight"><pre><span class="l">description "S3QL Backup File System"</span>
<span class="l">author "Nikolaus Rath </span><span class="nv"><Nikolaus@rath.org></span><span class="l">"</span>
<span class="l"># This assumes that eth0 provides your internet connection</span>
<span class="l">start on (filesystem and net-device-up IFACE=eth0)</span>
<span class="l"># We can't use "stop on runlevel </span><span class="ge">[016]</span><span class="l">" because from that point on we</span>
<span class="l"># have only 10 seconds until the system shuts down completely.</span>
<span class="l">stop on starting rc RUNLEVEL=</span><span class="ge">[016]</span><span class="l"></span>
<span class="l"># Time to wait before sending SIGKILL to the daemon and</span>
<span class="l"># pre-stop script</span>
<span class="l">kill timeout 300</span>
<span class="l">env STORAGE_URL="s3://my-backup-bla"</span>
<span class="l">env MOUNTPOINT="/mnt/backup"</span>
<span class="l">env USER="myusername"</span>
<span class="l">env AUTHFILE="/path/to/authinfo2"</span>
<span class="l">expect stop</span>
<span class="l">script</span>
<span class="l"> # Redirect stdout and stderr into the system log</span>
<span class="l"> DIR=$(mktemp -d)</span>
<span class="l"> mkfifo "$DIR/LOG_FIFO"</span>
<span class="l"> logger -t s3ql -p local0.info </span><span class="nv">< "$DIR/LOG_FIFO" &</span>
<span class="nv"> exec ></span><span class="l"> "$DIR/LOG_FIFO"</span>
<span class="l"> exec 2>&1</span>
<span class="l"> rm -rf "$DIR"</span>
<span class="l"> # Check and mount file system</span>
<span class="l"> su -s /bin/sh -c 'exec "$0" "$@"' "$USER" -- \</span>
<span class="l"> fsck.s3ql --batch --authfile "$AUTHFILE" "$STORAGE_URL"</span>
<span class="l"> exec su -s /bin/sh -c 'exec "$0" "$@"' "$USER" -- \</span>
<span class="l"> mount.s3ql --upstart --authfile "$AUTHFILE" "$STORAGE_URL" "$MOUNTPOINT"</span>
<span class="l">end script</span>
<span class="l">pre-stop script</span>
<span class="l"> su -s /bin/sh -c 'exec "$0" "$@"' "$USER" -- umount.s3ql "$MOUNTPOINT"</span>
<span class="l">end script</span>
</pre></div>
</td></tr></table></div>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p>In principle, it is also possible to automatically mount an S3QL
file system with an appropriate entry in <tt class="docutils literal"><span class="pre">/etc/fstab</span></tt>. However,
this is not recommended for several reasons:</p>
<ul class="last simple">
<li>file systems mounted in <tt class="docutils literal"><span class="pre">/etc/fstab</span></tt> will be unmounted with the
<tt class="docutils literal"><span class="pre">umount</span></tt> command, so your system will not wait until all data has
been uploaded but shutdown (or restart) immediately (this is a
FUSE limitation, see <a class="reference external" href="http://code.google.com/p/s3ql/issues/detail?id=159">issue 159</a>).</li>
<li>There is no way to tell the system that mounting S3QL requires a
Python interpreter to be available, so it may attempt to run
<tt class="docutils literal"><span class="pre">mount.s3ql</span></tt> before it has mounted the volume containing the
Python interpreter.</li>
<li>There is no standard way to tell the system that internet
connection has to be up before the S3QL file system can be
mounted.</li>
</ul>
</div>
</div>
</div>
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<ul>
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