191 lines
6.4 KiB
XML
191 lines
6.4 KiB
XML
<refentry 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-nix-channel">
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<refmeta>
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<refentrytitle>nix-channel</refentrytitle>
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<manvolnum>1</manvolnum>
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<refmiscinfo class="source">Nix</refmiscinfo>
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<refmiscinfo class="version"><xi:include href="../version.txt" parse="text"/></refmiscinfo>
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</refmeta>
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<refnamediv>
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<refname>nix-channel</refname>
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<refpurpose>manage Nix channels</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<cmdsynopsis>
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<command>nix-channel</command>
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<group choice='req'>
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<arg choice='plain'><option>--add</option> <replaceable>url</replaceable> <arg choice='opt'><replaceable>name</replaceable></arg></arg>
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<arg choice='plain'><option>--remove</option> <replaceable>name</replaceable></arg>
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<arg choice='plain'><option>--list</option></arg>
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<arg choice='plain'><option>--update</option> <arg rep='repeat'><replaceable>names</replaceable></arg></arg>
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<arg choice='plain'><option>--rollback</option> <arg choice='opt'><replaceable>generation</replaceable></arg></arg>
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</group>
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</cmdsynopsis>
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</refsynopsisdiv>
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<refsection><title>Description</title>
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<para>A Nix channel is a mechanism that allows you to automatically stay
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up-to-date with a set of pre-built Nix expressions. A Nix channel is
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just a URL that points to a place containing both a set of Nix
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expressions and a pointer to a binary cache. <phrase
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condition="manual">See also <xref linkend="sec-channels"
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/>.</phrase></para>
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<para>This command has the following operations:
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<variablelist>
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<varlistentry><term><option>--add</option> <replaceable>url</replaceable> [<replaceable>name</replaceable>]</term>
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<listitem><para>Adds a channel named
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<replaceable>name</replaceable> with URL
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<replaceable>url</replaceable> to the list of subscribed channels.
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If <replaceable>name</replaceable> is omitted, it defaults to the
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last component of <replaceable>url</replaceable>, with the
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suffixes <literal>-stable</literal> or
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<literal>-unstable</literal> removed.</para></listitem>
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</varlistentry>
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<varlistentry><term><option>--remove</option> <replaceable>name</replaceable></term>
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<listitem><para>Removes the channel named
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<replaceable>name</replaceable> from the list of subscribed
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channels.</para></listitem>
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</varlistentry>
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<varlistentry><term><option>--list</option></term>
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<listitem><para>Prints the names and URLs of all subscribed
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channels on standard output.</para></listitem>
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</varlistentry>
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<varlistentry><term><option>--update</option> [<replaceable>names</replaceable>…]</term>
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<listitem><para>Downloads the Nix expressions of all subscribed
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channels (or only those included in
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<replaceable>names</replaceable> if specified) and makes them the
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default for <command>nix-env</command> operations (by symlinking
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them from the directory
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<filename>~/.nix-defexpr</filename>).</para></listitem>
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</varlistentry>
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<varlistentry><term><option>--rollback</option> [<replaceable>generation</replaceable>]</term>
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<listitem><para>Reverts the previous call to <command>nix-channel
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--update</command>. Optionally, you can specify a specific channel
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generation number to restore.</para></listitem>
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</varlistentry>
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</variablelist>
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</para>
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<para>Note that <option>--add</option> does not automatically perform
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an update.</para>
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<para>The list of subscribed channels is stored in
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<filename>~/.nix-channels</filename>.</para>
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</refsection>
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<refsection><title>Examples</title>
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<para>To subscribe to the Nixpkgs channel and install the GNU Hello package:</para>
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<screen>
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$ nix-channel --add https://nixos.org/channels/nixpkgs-unstable
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$ nix-channel --update
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$ nix-env -iA nixpkgs.hello</screen>
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<para>You can revert channel updates using <option>--rollback</option>:</para>
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<screen>
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$ nix-instantiate --eval -E '(import <nixpkgs> {}).lib.nixpkgsVersion'
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"14.04.527.0e935f1"
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$ nix-channel --rollback
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switching from generation 483 to 482
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$ nix-instantiate --eval -E '(import <nixpkgs> {}).lib.nixpkgsVersion'
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"14.04.526.dbadfad"
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</screen>
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</refsection>
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<refsection><title>Files</title>
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<variablelist>
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<varlistentry><term><filename>/nix/var/nix/profiles/per-user/<replaceable>username</replaceable>/channels</filename></term>
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<listitem><para><command>nix-channel</command> uses a
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<command>nix-env</command> profile to keep track of previous
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versions of the subscribed channels. Every time you run
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<command>nix-channel --update</command>, a new channel generation
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(that is, a symlink to the channel Nix expressions in the Nix store)
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is created. This enables <command>nix-channel --rollback</command>
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to revert to previous versions.</para></listitem>
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</varlistentry>
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<varlistentry><term><filename>~/.nix-defexpr/channels</filename></term>
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<listitem><para>This is a symlink to
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<filename>/nix/var/nix/profiles/per-user/<replaceable>username</replaceable>/channels</filename>. It
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ensures that <command>nix-env</command> can find your channels. In
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a multi-user installation, you may also have
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<filename>~/.nix-defexpr/channels_root</filename>, which links to
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the channels of the root user.</para></listitem>
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</varlistentry>
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</variablelist>
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</refsection>
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<refsection><title>Channel format</title>
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<para>A channel URL should point to a directory containing the
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following files:</para>
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<variablelist>
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<varlistentry><term><filename>nixexprs.tar.xz</filename></term>
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<listitem><para>A tarball containing Nix expressions and files
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referenced by them (such as build scripts and patches). At the
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top level, the tarball should contain a single directory. That
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directory must contain a file <filename>default.nix</filename>
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that serves as the channel’s “entry point”.</para></listitem>
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</varlistentry>
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<varlistentry><term><filename>binary-cache-url</filename></term>
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<listitem><para>A file containing the URL to a binary cache (such
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as <uri>https://cache.nixos.org</uri>). Nix will automatically
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check this cache for pre-built binaries, if the user has
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sufficient rights to add binary caches. For instance, in a
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multi-user Nix setup, the binary caches provided by the channels
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of the root user are used automatically, but caches corresponding
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to the channels of non-root users are ignored.</para></listitem>
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</varlistentry>
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</variablelist>
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</refsection>
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</refentry>
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