95 lines
		
	
	
		
			3.1 KiB
		
	
	
	
		
			XML
		
	
	
	
	
	
		
		
			
		
	
	
			95 lines
		
	
	
		
			3.1 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="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-unstable</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 done using the following command:
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								<screen>
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								$ nixos-checkout <replaceable>/my/sources</replaceable>
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								</screen>
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								or
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								<screen>
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								$ mkdir -p <replaceable>/my/sources</replaceable>
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								$ cd <replaceable>/my/sources</replaceable>
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								$ nix-env -i git
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								$ git clone git://github.com/NixOS/nixpkgs.git
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								</screen>
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								This will check out the latest NixOS sources to
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								<filename><replaceable>/my/sources</replaceable>/nixpkgs/nixos</filename>
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								and the Nixpkgs sources to
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								<filename><replaceable>/my/sources</replaceable>/nixpkgs</filename>.
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								(The NixOS source tree lives in a subdirectory of the Nixpkgs
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								repository.)</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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								14.04.273.ea1952b (Baboon)
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								$ git checkout -b local ea1952b
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								</screen>
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								Or, to base your local branch on the latest version available in the
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								NixOS channel:
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								<screen>
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								$ curl -sI http://nixos.org/channels/nixos-unstable/ | grep Location
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								Location: http://releases.nixos.org/nixos/unstable/nixos-14.10pre43986.acaf4a6/
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								$ git checkout -b local acaf4a6
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								</screen>
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								You can then use <command>git rebase</command> to sync your local
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								branch with the upstream branch, and use <command>git
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								cherry-pick</command> to copy commits from your local branch to the
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								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.</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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