122 lines
4.0 KiB
XML
122 lines
4.0 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-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 <command>nix-build</command>, you can build specific parts
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of your NixOS configuration. This is done as follows:
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<screen>
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<prompt>$ </prompt>cd <replaceable>/path/to/nixpkgs/nixos</replaceable>
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<prompt>$ </prompt>nix-build -A config.<replaceable>option</replaceable></screen>
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where <replaceable>option</replaceable> is a NixOS option with type
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“derivation” (i.e. something that can be built). Attributes of interest
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include:
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<variablelist>
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<varlistentry>
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<term>
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<varname>system.build.toplevel</varname>
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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. Everything else
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in your configuration is indirectly pulled in by this option. This is
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what <command>nixos-rebuild</command> builds and what
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<filename>/run/current-system</filename> points 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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<screen>
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<prompt>$ </prompt>nix-build -A system</screen>
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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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<varname>system.build.manual.manualHTML</varname>
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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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<varname>system.build.etc</varname>
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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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<filename>/etc</filename>.
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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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<varname>system.build.initialRamdisk</varname>
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</term>
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<term>
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<varname>system.build.kernel</varname>
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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 quick way to
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test whether the kernel and the initial ramdisk boot correctly, by using
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QEMU’s <option>-kernel</option> and <option>-initrd</option> options:
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<screen>
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<prompt>$ </prompt>nix-build -A config.system.build.initialRamdisk -o initrd
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<prompt>$ </prompt>nix-build -A config.system.build.kernel -o kernel
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<prompt>$ </prompt>qemu-system-x86_64 -kernel ./kernel/bzImage -initrd ./initrd/initrd -hda /dev/null
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</screen>
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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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<varname>system.build.nixos-rebuild</varname>
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</term>
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<term>
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<varname>system.build.nixos-install</varname>
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</term>
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<term>
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<varname>system.build.nixos-generate-config</varname>
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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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<varname>systemd.units.<replaceable>unit-name</replaceable>.unit</varname>
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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 unit names
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contain dots (e.g. <literal>httpd.service</literal>), you need to put
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them between quotes, like this:
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<screen>
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<prompt>$ </prompt>nix-build -A 'config.systemd.units."httpd.service".unit'
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</screen>
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You can also test individual units, without rebuilding the whole system,
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by putting them in <filename>/run/systemd/system</filename>:
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<screen>
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<prompt>$ </prompt>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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<prompt># </prompt>systemctl daemon-reload
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<prompt># </prompt>systemctl start tmp-httpd.service
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</screen>
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Note that the unit must not have the same name as any unit in
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<filename>/etc/systemd/system</filename> since those take precedence over
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<filename>/run/systemd/system</filename>. That’s why the unit is
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installed as <filename>tmp-httpd.service</filename> 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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</para>
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</chapter>
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