58 lines
2 KiB
XML
58 lines
2 KiB
XML
<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 and upgrade using <command>nix-env</command>.
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Fortunately, there’s a better way: <emphasis>Nix
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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 https://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. (Subscribing really just means that
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the URL is added to the file <filename>~/.nix-channels</filename>,
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where it is read by subsequent calls to <command>nix-channel
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--update</command>.) You can “unsubscribe” using <command>nix-channel
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--remove</command>:
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<screen>
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$ nix-channel --remove nixpkgs
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</screen>
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</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 and unpacks the Nix expressions in every channel
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(downloaded from <literal><replaceable>url</replaceable>/nixexprs.tar.bz2</literal>).
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It also makes the union of each channel’s Nix expressions available by
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default to <command>nix-env</command> operations (via the symlink
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<filename>~/.nix-defexpr/channels</filename>). Consequently, you can
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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>
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