390 lines
12 KiB
XML
390 lines
12 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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<title>Installation</title>
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<!--===============================================================-->
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<section>
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<title>Building the installation CD</title>
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<para>Instead of building an installation CD, you could just download
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one from <link xlink:href="http://nixos.org/nixos/"/>. If you want
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(or need) to build it yourself:
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<orderedlist>
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<listitem><para>Make sure that you have a <emphasis>very</emphasis>
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recent pre-release version of Nix installed (<link
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xlink:href="http://nixos.org/releases/nix/nix-unstable/"/>).
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The NixOS Nix expressions frequently use bleeding-edge features. If
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you get any kind of expression evaluation error, try to upgrade your
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Nix.</para></listitem>
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<listitem><para>Optional but strongly recommended (and currently
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<emphasis>required</emphasis> for building the
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<literal>x86_64</literal> ISO): subscribe/pull from the Nixpkgs
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channel to speed up building, i.e.,
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<screen>
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$ nix-channel --add http://nixos.org/releases/nixpkgs/channels/nixpkgs-unstable
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$ nix-channel --update</screen>
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</para></listitem>
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<listitem><para>Check out NixOS from <link
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xlink:href="https://svn.nixos.org/repos/nix/nixos/trunk"/> as
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<literal>nixos</literal>.</para></listitem>
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<listitem><para>If you don’t already have Nixpkgs checkout, Check
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out Nixpkgs from <link
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xlink:href="https://svn.nixos.org/repos/nix/nixos/trunk"/> as
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<literal>nixpkgs</literal>.</para></listitem>
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<listitem><para>In the directory <literal>nixos</literal>, make a
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symbolic link <literal>pkgs</literal> to the <literal>pkgs</literal>
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directory of the Nixpkgs tree, e.g.,
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<screen>
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$ ln -s nixpkgs/pkgs nixos/</screen>
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</para></listitem>
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<listitem><para>Build the ISO image:
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<screen>
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$ nix-build configuration/rescue-cd.nix -A rescueCD</screen>
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If everything goes well, you’ll end up with an ISO image in
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<filename>./result/iso/nixos-<replaceable>version</replaceable>-<replaceable>platform</replaceable>.iso</filename>
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that you can burn onto a CD or attach to a virtual CD-ROM drive in
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your favourite virtual machine software.</para></listitem>
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</orderedlist>
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</para>
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</section>
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<!--===============================================================-->
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<section>
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<title>Installation</title>
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<orderedlist>
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<listitem><para>Boot from the CD.</para></listitem>
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<listitem><para>The CD contains a basic NixOS installation. (It
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also contain Memtest86+, useful if you want to test new hardware.)
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When it’s finished booting, it should have detected most of your
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hardware and brought up networking (check
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<command>ifconfig</command>). Networking is necessary for the
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installer, since it will download lots of stuff (such as source
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tarballs or Nixpkgs channel binaries). It’s best if you have a DHCP
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server on your network. Otherwise configure
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manually.</para></listitem>
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<listitem><para>The NixOS manual is available on virtual console 7
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(press Alt+F7 to access).</para></listitem>
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<listitem><para>Login as <literal>root</literal>, empty
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password.</para></listitem>
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<listitem><para>The NixOS installer doesn’t do any partitioning or
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formatting yet, so you need to that yourself. Use the following
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commands:
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<itemizedlist>
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<listitem><para>For partitioning:
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<command>fdisk</command>.</para></listitem>
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<listitem><para>For initialising Ext2/Ext3 partitions:
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<command>mke2fs</command>. Ext3 is recommended; use the
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<option>-j</option> to create a journalled file system. It is
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also recommended that you assign a unique symbolic label to the
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file system using the option <option>-L
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<replaceable>label</replaceable></option>. This will make the
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file system configuration independent from device
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changes.</para></listitem>
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<listitem><para>For creating swap partitions:
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<command>mkswap</command>. Again it’s recommended to assign a
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label to the swap partition: <option>-L
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<replaceable>label</replaceable></option>.</para></listitem>
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<listitem><para>For creating LVM volumes, the LVM commands, e.g.,
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<screen>
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$ pvcreate /dev/sda1 /dev/sdb1
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$ vgcreate MyVolGroup /dev/sda1 /dev/sdb1
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$ lvcreate --size 2G --name bigdisk MyVolGroup
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$ lvcreate --size 1G --name smalldisk MyVolGroup</screen>
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Possibly you’ll need to do <userinput>initctl start
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lvm</userinput> after this (TODO: check whether this is
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needed).</para></listitem>
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<listitem><para>For creating software RAID devices:
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<command>mdadm</command>.</para></listitem>
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</itemizedlist>
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</para></listitem>
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<listitem><para>Mount the target file system on
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<filename>/mnt</filename>.</para></listitem>
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<listitem>
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<para>The installation is declarative; you need to write a
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description of the configuration that you want to be built and
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activated. The configuration is specified in a Nix expression and
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must be stored <emphasis>on the target file system</emphasis> in
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<filename>/mnt/etc/nixos/configuration.nix</filename>. See
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<filename>/etc/nixos/nixos/configuration/examples</filename> for
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example machine configurations. You can copy and edit one of
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those (e.g., copy
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<filename>/etc/nixos/nixos/configuration/examples/basic.nix</filename>
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to <filename>/mnt/etc/nixos/configuration.nix</filename>). See
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<xref linkend="ch-options"/> for a list of the available
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configuration options. The text editors <command>nano</command>
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and <command>vim</command> are available.</para>
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<para>In particular you need to specify a root file system in
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<option>fileSystems</option> and the target device for the Grub
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boot loader in <option>boot.grubDevice</option>.</para>
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<para>The command <command>nixos-hardware-scan</command> can
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generate an initial configuration file for you, i.e.,
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<screen>
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$ mkdir -p /mnt/etc/nixos
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$ nixos-hardware-scan > /mnt/etc/nixos/configuration.nix</screen>
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It tries to figure out the modules necessary for mounting the root
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device, as well as various other hardware characteristics.
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However, it doesn’t try to figure out the
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<option>fileSystems</option> option yet.</para>
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<para>More examples of NixOS configurations for some actual
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machines can be found at <link
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xlink:href="https://svn.nixos.org/repos/nix/configurations/trunk/"/>.</para>
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<note><para>It is very important that you specify in the option
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<option>boot.initrd.extraKernelModules</option> all kernel modules
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that are necessary for mounting the root file system, otherwise
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the installed system will not be able to boot. (If this happens,
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boot from CD again, mount the target file system on
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<filename>/mnt</filename>, fix
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<filename>/mnt/etc/nixos/configuration.nix</filename> and rerun
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<filename>nixos-install</filename>.)
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<command>nixos-hardware-scan</command> should figure out the
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required modules in most cases.</para></note>
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</listitem>
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<listitem><para>If your machine has a limited amount of memory, you
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may want to activate swap devices now (<command>swapon
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<replaceable>device</replaceable></command>). The installer (or
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rather, the build actions that it may spawn) may need quite a bit of
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RAM, depending on your configuration.</para></listitem>
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<listitem><para>Optionally, you can run
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<screen>
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$ nixos-checkout</screen>
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to make the installer use the latest NixOS/Nixpkgs sources from the
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Subversion repository, rather than the sources on CD.</para></listitem>
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<listitem><para>Do the installation:
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<screen>
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$ nixos-install</screen>
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Cross fingers.</para></listitem>
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<listitem><para>If everything went well:
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<screen>
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$ reboot</screen>
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</para></listitem>
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<listitem>
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<para>You should now be able to boot into the installed NixOS.
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The Grub boot menu shows a list of <emphasis>available
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configurations</emphasis> (initially just one). Every time you
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change the NixOS configuration (see <xref
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linkend="sec-changing-config" />), a new item appears in the menu.
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This allows you to go back easily to another configuration if
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something goes wrong.</para>
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<para>You should log in and change the <literal>root</literal>
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password with <command>passwd</command>.</para>
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<para>You’ll probably want to create some user accounts as well,
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which can be done with <command>useradd</command>:
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<screen>
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$ useradd -c 'Eelco Dolstra' -m eelco
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$ passwd eelco</screen>
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</para>
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<para>You may also want to install some software. For instance,
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<screen>
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$ nix-env -qa \*</screen>
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shows what packages are available, and
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<screen>
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$ nix-env -i w3m</screen>
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install the <literal>w3m</literal> browser.</para>
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</listitem>
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</orderedlist>
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<para><xref linkend="ex-install-sequence" /> shows a typical sequence
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of commands for installing NixOS on an empty hard drive (here
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<filename>/dev/sda). <xref linkend="ex-config" /> shows a
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corresponding configuration Nix expression.</filename>
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</para>
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<example xml:id='ex-install-sequence'><title>Commands for installing NixOS on <filename>/dev/sda</filename></title>
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<screen>
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$ fdisk /dev/sda <lineannotation>(or whatever device you want to install on)</lineannotation>
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$ mke2fs -j -L nixos /dev/sda1 <lineannotation>(idem)</lineannotation>
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$ mkswap -L swap /dev/sda2 <lineannotation>(idem)</lineannotation>
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$ mount LABEL=nixos /mnt
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$ mkdir -p /mnt/etc/nixos
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$ nixos-hardware-scan > /mnt/etc/nixos/configuration.nix
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$ nano /mnt/etc/nixos/configuration.nix
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<lineannotation>(in particular, set the fileSystems and swapDevices options)</lineannotation>
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$ nixos-install
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$ reboot</screen>
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</example>
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<example xml:id='ex-config'><title>NixOS configuration</title>
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<screen>
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{
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boot = {
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initrd = {
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extraKernelModules = [ "ata_piix" ];
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};
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grubDevice = "/dev/sda";
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};
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fileSystems = [
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{ mountPoint = "/";
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label = "nixos";
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}
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];
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swapDevices = [
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{ label = "swap"; }
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];
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services = {
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sshd = {
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enable = true;
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};
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};
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}</screen>
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</example>
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</section>
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<!--===============================================================-->
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<section xml:id="sec-changing-config">
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<title>Changing the configuration</title>
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<para>The file <filename>/etc/nixos/configuration.nix</filename>
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contains the current configuration of your machine. Whenever you’ve
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changed something to that file, or to the NixOS/Nixpkgs sources in
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<filename>/etc/nixos/nixos</filename> and
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<filename>/etc/nixos/nixpkgs</filename>, respectively, you should do
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<screen>
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$ nixos-rebuild switch</screen>
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to build the new configuration, make it the default configuration for
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booting, and try to effect the configuration in the running system
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(e.g., by restarting system services).</para>
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<para>You can also do
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<screen>
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$ nixos-rebuild test</screen>
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to build the configuration and switch the running system to it, but
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without making it the boot default. So if (say) the configuration
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locks up your machine, you can just reboot to get back to a working
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configuration.</para>
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<para>There is also
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<screen>
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$ nixos-rebuild boot</screen>
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to build the configuration and make it the boot default, but not
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switch to it now (so it will only take effect after the next
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reboot).</para>
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<para>Finally, you can do
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<screen>
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$ nixos-rebuild build</screen>
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to build the configuration but nothing more. This is useful to see
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whether everything compiles cleanly.</para>
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</section>
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<!--===============================================================-->
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<section>
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<title>Keeping NixOS up to date</title>
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<para>The currently best way to keep your NixOS installation up to
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date is to track the NixOS Subversion repository. You should replace
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the static NixOS/Nixpkgs sources installed in
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<filename>/etc/nixos</filename> with a Subversion checkout. The
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program <command>nixos-checkout</command> does that for you (and it
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also installs Subversion into your current profile).</para>
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<para>To build the latest and greatest, do
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<screen>
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$ svn up /etc/nixos/nixos
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$ svn up /etc/nixos/nixpkgs
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$ nixos-rebuild switch</screen>
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(Or instead of <literal>switch</literal>, use any of the alternatives
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shown in <xref linkend="sec-changing-config"/>.)</para>
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</section>
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</chapter>
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