124 lines
4 KiB
XML
124 lines
4 KiB
XML
<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xml:id="sec-building-parts">
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<title>Building Specific Parts of NixOS</title>
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<para>
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With the command <literal>nix-build</literal>, you can build
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specific parts of your NixOS configuration. This is done as follows:
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</para>
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<programlisting>
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$ cd /path/to/nixpkgs/nixos
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$ nix-build -A config.option
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</programlisting>
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<para>
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where <literal>option</literal> is a NixOS option with type
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<quote>derivation</quote> (i.e. something that can be built).
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Attributes of interest include:
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</para>
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<variablelist>
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<varlistentry>
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<term>
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<literal>system.build.toplevel</literal>
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</term>
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<listitem>
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<para>
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The top-level option that builds the entire NixOS system.
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Everything else in your configuration is indirectly pulled in
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by this option. This is what <literal>nixos-rebuild</literal>
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builds and what <literal>/run/current-system</literal> points
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to afterwards.
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</para>
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<para>
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A shortcut to build this is:
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</para>
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<programlisting>
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$ nix-build -A system
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</programlisting>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<literal>system.build.manual.manualHTML</literal>
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</term>
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<listitem>
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<para>
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The NixOS manual.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<literal>system.build.etc</literal>
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</term>
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<listitem>
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<para>
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A tree of symlinks that form the static parts of
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<literal>/etc</literal>.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<literal>system.build.initialRamdisk</literal> ,
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<literal>system.build.kernel</literal>
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</term>
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<listitem>
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<para>
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The initial ramdisk and kernel of the system. This allows a
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quick way to test whether the kernel and the initial ramdisk
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boot correctly, by using QEMU’s <literal>-kernel</literal> and
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<literal>-initrd</literal> options:
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</para>
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<programlisting>
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$ nix-build -A config.system.build.initialRamdisk -o initrd
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$ nix-build -A config.system.build.kernel -o kernel
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$ qemu-system-x86_64 -kernel ./kernel/bzImage -initrd ./initrd/initrd -hda /dev/null
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</programlisting>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<literal>system.build.nixos-rebuild</literal> ,
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<literal>system.build.nixos-install</literal> ,
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<literal>system.build.nixos-generate-config</literal>
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</term>
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<listitem>
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<para>
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These build the corresponding NixOS commands.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<literal>systemd.units.unit-name.unit</literal>
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</term>
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<listitem>
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<para>
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This builds the unit with the specified name. Note that since
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unit names contain dots (e.g.
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<literal>httpd.service</literal>), you need to put them
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between quotes, like this:
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</para>
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<programlisting>
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$ nix-build -A 'config.systemd.units."httpd.service".unit'
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</programlisting>
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<para>
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You can also test individual units, without rebuilding the
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whole system, by putting them in
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<literal>/run/systemd/system</literal>:
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</para>
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<programlisting>
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$ cp $(nix-build -A 'config.systemd.units."httpd.service".unit')/httpd.service \
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/run/systemd/system/tmp-httpd.service
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# systemctl daemon-reload
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# systemctl start tmp-httpd.service
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</programlisting>
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<para>
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Note that the unit must not have the same name as any unit in
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<literal>/etc/systemd/system</literal> since those take
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precedence over <literal>/run/systemd/system</literal>. That’s
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why the unit is installed as
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<literal>tmp-httpd.service</literal> here.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</chapter>
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