2014-09-16 13:39:08 +00:00
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<section xmlns="http://docbook.org/ns/docbook"
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2014-08-27 16:41:09 +00:00
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xmlns:xlink="http://www.w3.org/1999/xlink"
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xmlns:xi="http://www.w3.org/2001/XInclude"
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version="5.0"
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2014-09-16 13:39:08 +00:00
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xml:id="sec-links-nix-store">
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2014-08-27 16:41:09 +00:00
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<title><quote>Too many links</quote> Error in the Nix store</title>
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<para>Symptom: when building something, you get an error message such as
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<screen>
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...
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<literal>mkdir: cannot create directory `/nix/store/<replaceable>name</replaceable>': Too many links</literal></screen>
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</para>
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<para>This is usually because you have more than 32,000 subdirectories
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in <filename>/nix/store</filename>, as can be seen using <command>ls
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-l</command>:
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<screen>
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2014-12-13 22:23:19 +00:00
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$ ls -ld /nix/store
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2014-08-27 16:41:09 +00:00
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drwxrwxrwt 32000 nix nix 4620288 Sep 8 15:08 store</screen>
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The <literal>ext2</literal> file system is limited to an inode link
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count of 32,000 (each subdirectory increasing the count by one).
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Furthermore, the <literal>st_nlink</literal> field of the
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<function>stat</function> system call is a 16-bit value.</para>
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<para>This only happens on very large Nix installations (such as build
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machines).</para>
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<para>Quick solution: run the garbage collector. You may want to use
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the <option>--max-links</option> option.</para>
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<para>Real solution: put the Nix store on a file system that supports
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2014-12-13 22:23:19 +00:00
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more than 32,000 subdirectories per directory, such as ext4. (This
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doesn’t solve the <literal>st_nlink</literal> limit, but ext4 lies to
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the kernel by reporting a link count of 1 if it exceeds the
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limit.)</para>
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2014-08-27 16:41:09 +00:00
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2014-09-16 13:39:08 +00:00
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</section>
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