43 lines
1.7 KiB
XML
43 lines
1.7 KiB
XML
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<chapter xmlns="http://docbook.org/ns/docbook"
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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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xml:id="ch-collisions-nixenv">
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<title>Collisions in <command>nix-env</command></title>
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<para>Symptom: when installing or upgrading, you get an error message such as
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<screen>
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$ nix-env -i docbook-xml
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...
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adding /nix/store/s5hyxgm62gk2...-docbook-xml-4.2
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collision between `/nix/store/s5hyxgm62gk2...-docbook-xml-4.2/xml/dtd/docbook/calstblx.dtd'
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and `/nix/store/06h377hr4b33...-docbook-xml-4.3/xml/dtd/docbook/calstblx.dtd'
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at /nix/store/...-builder.pl line 62.</screen>
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</para>
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<para>The cause is that two installed packages in the user environment
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have overlapping filenames (e.g.,
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<filename>xml/dtd/docbook/calstblx.dtd</filename>. This usually
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happens when you accidentally try to install two versions of the same
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package. For instance, in the example above, the Nix Packages
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collection contains two versions of <literal>docbook-xml</literal>, so
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<command>nix-env -i</command> will try to install both. The default
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user environment builder has no way to way to resolve such conflicts,
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so it just gives up.</para>
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<para>Solution: remove one of the offending packages from the user
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environment (if already installed) using <command>nix-env
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-e</command>, or specify exactly which version should be installed
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(e.g., <literal>nix-env -i docbook-xml-4.2</literal>).</para>
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<para>Alternatively, you can modify the user environment builder
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script (in
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<filename><replaceable>prefix</replaceable>/share/nix/corepkgs/buildenv/builder.pl</filename>)
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to implement some conflict resolution policy. E.g., the script could
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be modified to rename conflicting file names, or to pick one over the
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other.</para>
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</chapter>
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