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<ol class="chapter"><li class="chapter-item expanded affix "><a href="../intro.html">Introduction</a></li><li class="chapter-item expanded "><a href="../shells/index.html"><strong aria-hidden="true">1.</strong> Shells</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../shells/zsh.html"><strong aria-hidden="true">1.1.</strong> zsh</a></li><li class="chapter-item expanded "><a href="../shells/bash.html"><strong aria-hidden="true">1.2.</strong> bash</a></li><li class="chapter-item expanded "><a href="../shells/fish.html"><strong aria-hidden="true">1.3.</strong> fish</a></li></ol></li><li class="chapter-item expanded "><a href="../cli/index.html"><strong aria-hidden="true">2.</strong> CLI foo</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../cli/awk.html"><strong aria-hidden="true">2.1.</strong> awk</a></li><li class="chapter-item expanded "><a href="../cli/sed.html"><strong aria-hidden="true">2.2.</strong> sed</a></li><li 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<h1 id="access-control-list-acl"><a class="header" href="#access-control-list-acl">access control list (acl)</a></h1>
<blockquote>
<p>This describes <code>POSIX</code> acl.</p>
</blockquote>
<p>The access control list provides a flexibel permission mechanism next to the
<code>UNIX</code> file permissions. This allows to specify fine grained permissions for
users/groups on filesystems.</p>
<p>Filesystems which support acl typically have an <code>acl</code> option, which must be
specified while mounting when it is not a default option.
Filesystems must be mounted with the <code>acl</code> option if not enabled as default
option.</p>
<p>Files or folder that have an <code>acl</code> defined, can be identified by the <code>+</code> sign
next to the UNIX permissions.</p>
<p>The following shows on example for a zfs filesystem.</p>
<pre><code class="language-bash"># mount | grep tank
tank on /tank type zfs (rw,xattr,noacl)
tank/foo on /tank/foo type zfs (rw,xattr,posixacl)
# ls -h /tank
drwxrwxr-x+ 2 root root 4 11. Jun 14:26 foo/
</code></pre>
<h2 id="show-acl-entries"><a class="header" href="#show-acl-entries">Show acl entries</a></h2>
<pre><code class="language-bash"># List current acl entries.
getfacl /tank/foo
</code></pre>
<h2 id="modify-acl-entries"><a class="header" href="#modify-acl-entries">Modify acl entries</a></h2>
<pre><code class="language-bash"># Add acl entry for user "user123".
setfacl -m "u:user123:rwx" /tank/foo
# Remove entry for user "user123".
setfacl -x "u:user123" /tank/foo
# Add acl entry for group "group456".
setfacl -m "g:group456:rx" /tank/foo
# Add acl entry for others.
setfacl -m "o:rx" /tank/foo
# Remove extended acl entries.
setfacl -b /tank/foo
</code></pre>
<h2 id="masking-of-acl-entries"><a class="header" href="#masking-of-acl-entries">Masking of acl entries</a></h2>
<p>The <code>mask</code> defines the maximum access rights that can be given to <strong>users</strong> and
<strong>groups</strong>.</p>
<pre><code class="language-bash"># Update the mask.
setfacl -m "m:rx" /tank/foo
# List acl entries.
getfacl /tank/foo
# file: tank/foo
# owner: root
# group: root
user::rwx
user:user123:rwx # effective:r-x
group::r-x
mask::r-x
other::rwx
</code></pre>
<h2 id="references"><a class="header" href="#references">References</a></h2>
<ul>
<li><a href="https://www.man7.org/linux/man-pages/man5/acl.5.html">acl(5)</a></li>
<li><a href="https://www.man7.org/linux/man-pages/man1/getfacl.1.html">getfacl(1)</a></li>
<li><a href="https://www.man7.org/linux/man-pages/man1/setfacl.1.html">setfacl(1)</a></li>
</ul>
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