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<td width="80%" align="center" valign="bottom">Chapter 9 Filesystem Structure</td>
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<h1 class="SECT1"><a id="FILESYSTEM-STRUCTURE-LINKS"
name="FILESYSTEM-STRUCTURE-LINKS">9.3 Links</a></h1>
<p>Links are pointers between files. With links, you can have files exist in many
locations and be accessible by many names. There are two types of links: hard and
soft.</p>
<p>Hard links are names for a particular file. They can only exist within a single
filesystem and are only removed when the real name is removed from the system. These are
useful in some cases, but many users find the soft link to be more versatile.</p>
<p>The soft link, also called a symbolic link, can point to a file outside of its
filesystem. It is actually a small file containing the information it needs. You can add
and remove soft links without affecting the actual file. And since a symbolic link is
actually a small file containing its own information, they can even point at a directory.
It's rather common to have <tt class="FILENAME">/var/tmp</tt> actually be a symbolic link
to <tt class="FILENAME">/tmp</tt> for example.</p>
<p>Links do not have their own set of permissions or ownerships, but instead reflect
those of the file they point to. Slackware uses mostly soft links. Here is a common
example:</p>
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<samp class="PROMPT">%</samp> <kbd class="USERINPUT">ls -l /bin/sh</kbd>
lrwxrwxrwx 1 root root 4 Apr 6 12:34 /bin/sh -> bash
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<p>The <tt class="COMMAND">sh</tt> shell under Slackware is actually <tt
class="COMMAND">bash</tt>. Removing links is done using <tt class="COMMAND">rm</tt>. The
<tt class="COMMAND">ln</tt> command is used to create links. These commands will be
discussed in more depth in <a href="file-commands.html">Chapter 10</a>.</p>
<p>It's very important to be careful about symlinks in particular. Once, I was working on
a machine that was consistently failing to back-up to tape each night. Two symlinks had
been made to directories beneath each other. The back-up software kept appending those
same directories to the tape until it was out of space. Normally, a set of checks will
prevent creating a symlink in this situation, but ours was a special case.</p>
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