103 lines
3.6 KiB
XML
103 lines
3.6 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-getting-sources">
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<title>Getting the Sources</title>
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<para>By default, NixOS’s <command>nixos-rebuild</command> command
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uses the NixOS and Nixpkgs sources provided by the
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<literal>nixos</literal> channel (kept in
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<filename>/nix/var/nix/profiles/per-user/root/channels/nixos</filename>).
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To modify NixOS, however, you should check out the latest sources from
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Git. This is as follows:
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<screen>
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$ git clone git://github.com/NixOS/nixpkgs.git
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$ cd nixpkgs
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$ git remote add channels git://github.com/NixOS/nixpkgs-channels.git
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$ git remote update channels
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</screen>
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This will check out the latest Nixpkgs sources to
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<filename>./nixpkgs</filename> the NixOS sources to
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<filename>./nixpkgs/nixos</filename>. (The NixOS source tree lives in
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a subdirectory of the Nixpkgs repository.) The remote
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<literal>channels</literal> refers to a read-only repository that
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tracks the Nixpkgs/NixOS channels (see <xref linkend="sec-upgrading"/>
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for more information about channels). Thus, the Git branch
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<literal>channels/nixos-17.03</literal> will contain the latest built
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and tested version available in the <literal>nixos-17.03</literal>
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channel.</para>
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<para>It’s often inconvenient to develop directly on the master
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branch, since if somebody has just committed (say) a change to GCC,
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then the binary cache may not have caught up yet and you’ll have to
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rebuild everything from source. So you may want to create a local
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branch based on your current NixOS version:
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<screen>
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$ nixos-version
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17.09pre104379.6e0b727 (Hummingbird)
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$ git checkout -b local 6e0b727
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</screen>
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Or, to base your local branch on the latest version available in a
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NixOS channel:
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<screen>
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$ git remote update channels
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$ git checkout -b local channels/nixos-17.03
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</screen>
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(Replace <literal>nixos-17.03</literal> with the name of the channel
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you want to use.) You can use <command>git merge</command> or
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<command>git rebase</command> to keep your local branch in sync with
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the channel, e.g.
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<screen>
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$ git remote update channels
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$ git merge channels/nixos-17.03
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</screen>
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You can use <command>git cherry-pick</command> to copy commits from
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your local branch to the upstream branch.</para>
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<para>If you want to rebuild your system using your (modified)
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sources, you need to tell <command>nixos-rebuild</command> about them
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using the <option>-I</option> flag:
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<screen>
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# nixos-rebuild switch -I nixpkgs=<replaceable>/my/sources</replaceable>/nixpkgs
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</screen>
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</para>
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<para>If you want <command>nix-env</command> to use the expressions in
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<replaceable>/my/sources</replaceable>, use <command>nix-env -f
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<replaceable>/my/sources</replaceable>/nixpkgs</command>, or change
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the default by adding a symlink in
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<filename>~/.nix-defexpr</filename>:
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<screen>
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$ ln -s <replaceable>/my/sources</replaceable>/nixpkgs ~/.nix-defexpr/nixpkgs
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</screen>
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You may want to delete the symlink
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<filename>~/.nix-defexpr/channels_root</filename> to prevent root’s
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NixOS channel from clashing with your own tree (this may break the
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command-not-found utility though). If you want to go back to the default
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state, you may just remove the <filename>~/.nix-defexpr</filename>
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directory completely, log out and log in again and it should have been
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recreated with a link to the root channels.</para>
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<!-- FIXME: not sure what this means.
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<para>You should not pass the base directory
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<filename><replaceable>/my/sources</replaceable></filename>
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to <command>nix-env</command>, as it will break after interpreting expressions
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in <filename>nixos/</filename> as packages.</para>
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-->
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</chapter>
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