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2.2 KiB
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57 lines
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2.2 KiB
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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="sec-channels">
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<title>Channels</title>
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<para>If you want to stay up to date with a set of packages, it’s not
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very convenient to manually download the latest set of Nix expressions
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for those packages, use <command>nix-pull</command> to register
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pre-built binaries (if available), and upgrade using
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<command>nix-env</command>. Fortunately, there’s a better way:
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<emphasis>Nix channels</emphasis>.</para>
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<para>A Nix channel is just a URL that points to a place that contains
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a set of Nix expressions and a manifest. Using the command <link
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linkend="sec-nix-channel"><command>nix-channel</command></link> you
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can automatically stay up to date with whatever is available at that
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URL.</para>
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<para>You can “subscribe” to a channel using
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<command>nix-channel --add</command>, e.g.,
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<screen>
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$ nix-channel --add http://nixos.org/channels/nixpkgs-unstable</screen>
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subscribes you to a channel that always contains that latest version
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of the Nix Packages collection. (Instead of
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<literal>nixpkgs-unstable</literal> you could also subscribe to
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<literal>nixpkgs-stable</literal>, which should have a higher level of
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stability, but right now is just outdated.) Subscribing really just
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means that the URL is added to the file
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<filename>~/.nix-channels</filename>. Right now there is no command
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to “unsubscribe”; you should just edit that file manually
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and delete the offending URL.</para>
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<para>To obtain the latest Nix expressions available in a channel, do
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<screen>
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$ nix-channel --update</screen>
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This downloads the Nix expressions in every channel (downloaded from
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<literal><replaceable>url</replaceable>/nixexprs.tar.bz2</literal>)
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and registers any available pre-built binaries in every channel
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(by <command>nix-pull</command>ing
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<literal><replaceable>url</replaceable>/MANIFEST</literal>). It also
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makes the union of each channel’s Nix expressions the default for
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<command>nix-env</command> operations. Consequently, you can then say
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<screen>
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$ nix-env -u '*'</screen>
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to upgrade all packages in your profile to the latest versions
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available in the subscribed channels.</para>
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</chapter> |