<chapter xmlns="http://docbook.org/ns/docbook"  xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" xml:id="sec-installation">
  <title>Installing NixOS</title>
  <section xml:id="sec-installation-booting">
    <title>Booting the system</title>
    <para>
      NixOS can be installed on BIOS or UEFI systems. The procedure for
      a UEFI installation is by and large the same as a BIOS
      installation. The differences are mentioned in the steps that
      follow.
    </para>
    <para>
      The installation media can be burned to a CD, or now more
      commonly, <quote>burned</quote> to a USB drive (see
      <xref linkend="sec-booting-from-usb" />).
    </para>
    <para>
      The installation media contains a basic NixOS installation. When
      it’s finished booting, it should have detected most of your
      hardware.
    </para>
    <para>
      The NixOS manual is available by running
      <literal>nixos-help</literal>.
    </para>
    <para>
      You are logged-in automatically as <literal>nixos</literal>. The
      <literal>nixos</literal> user account has an empty password so you
      can use <literal>sudo</literal> without a password:
    </para>
    <programlisting>
$ sudo -i
</programlisting>
    <para>
      If you downloaded the graphical ISO image, you can run
      <literal>systemctl start display-manager</literal> to start the
      desktop environment. If you want to continue on the terminal, you
      can use <literal>loadkeys</literal> to switch to your preferred
      keyboard layout. (We even provide neo2 via
      <literal>loadkeys de neo</literal>!)
    </para>
    <para>
      If the text is too small to be legible, try
      <literal>setfont ter-v32n</literal> to increase the font size.
    </para>
    <para>
      To install over a serial port connect with
      <literal>115200n8</literal> (e.g.
      <literal>picocom -b 115200 /dev/ttyUSB0</literal>). When the
      bootloader lists boot entries, select the serial console boot
      entry.
    </para>
    <section xml:id="sec-installation-booting-networking">
      <title>Networking in the installer</title>
      <para>
        The boot process should have brought up networking (check
        <literal>ip a</literal>). Networking is necessary for the
        installer, since it will download lots of stuff (such as source
        tarballs or Nixpkgs channel binaries). It’s best if you have a
        DHCP server on your network. Otherwise configure networking
        manually using <literal>ifconfig</literal>.
      </para>
      <para>
        On the graphical installer, you can configure the network, wifi
        included, through NetworkManager. Using the
        <literal>nmtui</literal> program, you can do so even in a
        non-graphical session. If you prefer to configure the network
        manually, disable NetworkManager with
        <literal>systemctl stop NetworkManager</literal>.
      </para>
      <para>
        On the minimal installer, NetworkManager is not available, so
        configuration must be perfomed manually. To configure the wifi,
        first start wpa_supplicant with
        <literal>sudo systemctl start wpa_supplicant</literal>, then run
        <literal>wpa_cli</literal>. For most home networks, you need to
        type in the following commands:
      </para>
      <programlisting>
&gt; add_network
0
&gt; set_network 0 ssid &quot;myhomenetwork&quot;
OK
&gt; set_network 0 psk &quot;mypassword&quot;
OK
&gt; set_network 0 key_mgmt WPA-PSK
OK
&gt; enable_network 0
OK
</programlisting>
      <para>
        For enterprise networks, for example
        <emphasis>eduroam</emphasis>, instead do:
      </para>
      <programlisting>
&gt; add_network
0
&gt; set_network 0 ssid &quot;eduroam&quot;
OK
&gt; set_network 0 identity &quot;myname@example.com&quot;
OK
&gt; set_network 0 password &quot;mypassword&quot;
OK
&gt; set_network 0 key_mgmt WPA-EAP
OK
&gt; enable_network 0
OK
</programlisting>
      <para>
        When successfully connected, you should see a line such as this
        one
      </para>
      <programlisting>
&lt;3&gt;CTRL-EVENT-CONNECTED - Connection to 32:85:ab:ef:24:5c completed [id=0 id_str=]
</programlisting>
      <para>
        you can now leave <literal>wpa_cli</literal> by typing
        <literal>quit</literal>.
      </para>
      <para>
        If you would like to continue the installation from a different
        machine you can use activated SSH daemon. You need to copy your
        ssh key to either
        <literal>/home/nixos/.ssh/authorized_keys</literal> or
        <literal>/root/.ssh/authorized_keys</literal> (Tip: For
        installers with a modifiable filesystem such as the sd-card
        installer image a key can be manually placed by mounting the
        image on a different machine). Alternatively you must set a
        password for either <literal>root</literal> or
        <literal>nixos</literal> with <literal>passwd</literal> to be
        able to login.
      </para>
    </section>
  </section>
  <section xml:id="sec-installation-partitioning">
    <title>Partitioning and formatting</title>
    <para>
      The NixOS installer doesn’t do any partitioning or formatting, so
      you need to do that yourself.
    </para>
    <para>
      The NixOS installer ships with multiple partitioning tools. The
      examples below use <literal>parted</literal>, but also provides
      <literal>fdisk</literal>, <literal>gdisk</literal>,
      <literal>cfdisk</literal>, and <literal>cgdisk</literal>.
    </para>
    <para>
      The recommended partition scheme differs depending if the computer
      uses <emphasis>Legacy Boot</emphasis> or
      <emphasis>UEFI</emphasis>.
    </para>
    <section xml:id="sec-installation-partitioning-UEFI">
      <title>UEFI (GPT)</title>
      <para>
        Here's an example partition scheme for UEFI, using
        <literal>/dev/sda</literal> as the device.
      </para>
      <note>
        <para>
          You can safely ignore <literal>parted</literal>'s
          informational message about needing to update /etc/fstab.
        </para>
      </note>
      <orderedlist numeration="arabic">
        <listitem>
          <para>
            Create a <emphasis>GPT</emphasis> partition table.
          </para>
          <programlisting>
# parted /dev/sda -- mklabel gpt
</programlisting>
        </listitem>
        <listitem>
          <para>
            Add the <emphasis>root</emphasis> partition. This will fill
            the disk except for the end part, where the swap will live,
            and the space left in front (512MiB) which will be used by
            the boot partition.
          </para>
          <programlisting>
# parted /dev/sda -- mkpart primary 512MiB -8GiB
</programlisting>
        </listitem>
        <listitem>
          <para>
            Next, add a <emphasis>swap</emphasis> partition. The size
            required will vary according to needs, here a 8GiB one is
            created.
          </para>
          <programlisting>
# parted /dev/sda -- mkpart primary linux-swap -8GiB 100%
</programlisting>
          <note>
            <para>
              The swap partition size rules are no different than for
              other Linux distributions.
            </para>
          </note>
        </listitem>
        <listitem>
          <para>
            Finally, the <emphasis>boot</emphasis> partition. NixOS by
            default uses the ESP (EFI system partition) as its
            <emphasis>/boot</emphasis> partition. It uses the initially
            reserved 512MiB at the start of the disk.
          </para>
          <programlisting>
# parted /dev/sda -- mkpart ESP fat32 1MiB 512MiB
# parted /dev/sda -- set 3 esp on
</programlisting>
        </listitem>
      </orderedlist>
      <para>
        Once complete, you can follow with
        <xref linkend="sec-installation-partitioning-formatting" />.
      </para>
    </section>
    <section xml:id="sec-installation-partitioning-MBR">
      <title>Legacy Boot (MBR)</title>
      <para>
        Here's an example partition scheme for Legacy Boot, using
        <literal>/dev/sda</literal> as the device.
      </para>
      <note>
        <para>
          You can safely ignore <literal>parted</literal>'s
          informational message about needing to update /etc/fstab.
        </para>
      </note>
      <orderedlist numeration="arabic">
        <listitem>
          <para>
            Create a <emphasis>MBR</emphasis> partition table.
          </para>
          <programlisting>
# parted /dev/sda -- mklabel msdos
</programlisting>
        </listitem>
        <listitem>
          <para>
            Add the <emphasis>root</emphasis> partition. This will fill
            the the disk except for the end part, where the swap will
            live.
          </para>
          <programlisting>
# parted /dev/sda -- mkpart primary 1MiB -8GiB
</programlisting>
        </listitem>
        <listitem>
          <para>
            Finally, add a <emphasis>swap</emphasis> partition. The size
            required will vary according to needs, here a 8GiB one is
            created.
          </para>
          <programlisting>
# parted /dev/sda -- mkpart primary linux-swap -8GiB 100%
</programlisting>
          <note>
            <para>
              The swap partition size rules are no different than for
              other Linux distributions.
            </para>
          </note>
        </listitem>
      </orderedlist>
      <para>
        Once complete, you can follow with
        <xref linkend="sec-installation-partitioning-formatting" />.
      </para>
    </section>
    <section xml:id="sec-installation-partitioning-formatting">
      <title>Formatting</title>
      <para>
        Use the following commands:
      </para>
      <itemizedlist>
        <listitem>
          <para>
            For initialising Ext4 partitions:
            <literal>mkfs.ext4</literal>. It is recommended that you
            assign a unique symbolic label to the file system using the
            option <literal>-L label</literal>, since this makes the
            file system configuration independent from device changes.
            For example:
          </para>
          <programlisting>
# mkfs.ext4 -L nixos /dev/sda1
</programlisting>
        </listitem>
        <listitem>
          <para>
            For creating swap partitions: <literal>mkswap</literal>.
            Again it’s recommended to assign a label to the swap
            partition: <literal>-L label</literal>. For example:
          </para>
          <programlisting>
# mkswap -L swap /dev/sda2
</programlisting>
        </listitem>
        <listitem>
          <para>
            <emphasis role="strong">UEFI systems</emphasis>
          </para>
          <para>
            For creating boot partitions: <literal>mkfs.fat</literal>.
            Again it’s recommended to assign a label to the boot
            partition: <literal>-n label</literal>. For example:
          </para>
          <programlisting>
# mkfs.fat -F 32 -n boot /dev/sda3
</programlisting>
        </listitem>
        <listitem>
          <para>
            For creating LVM volumes, the LVM commands, e.g.,
            <literal>pvcreate</literal>, <literal>vgcreate</literal>,
            and <literal>lvcreate</literal>.
          </para>
        </listitem>
        <listitem>
          <para>
            For creating software RAID devices, use
            <literal>mdadm</literal>.
          </para>
        </listitem>
      </itemizedlist>
    </section>
  </section>
  <section xml:id="sec-installation-installing">
    <title>Installing</title>
    <orderedlist numeration="arabic">
      <listitem>
        <para>
          Mount the target file system on which NixOS should be
          installed on <literal>/mnt</literal>, e.g.
        </para>
        <programlisting>
# mount /dev/disk/by-label/nixos /mnt
</programlisting>
      </listitem>
      <listitem>
        <para>
          <emphasis role="strong">UEFI systems</emphasis>
        </para>
        <para>
          Mount the boot file system on <literal>/mnt/boot</literal>,
          e.g.
        </para>
        <programlisting>
# mkdir -p /mnt/boot
# mount /dev/disk/by-label/boot /mnt/boot
</programlisting>
      </listitem>
      <listitem>
        <para>
          If your machine has a limited amount of memory, you may want
          to activate swap devices now
          (<literal>swapon device</literal>). The installer (or rather,
          the build actions that it may spawn) may need quite a bit of
          RAM, depending on your configuration.
        </para>
        <programlisting>
# swapon /dev/sda2
</programlisting>
      </listitem>
      <listitem>
        <para>
          You now need to create a file
          <literal>/mnt/etc/nixos/configuration.nix</literal> that
          specifies the intended configuration of the system. This is
          because NixOS has a <emphasis>declarative</emphasis>
          configuration model: you create or edit a description of the
          desired configuration of your system, and then NixOS takes
          care of making it happen. The syntax of the NixOS
          configuration file is described in
          <xref linkend="sec-configuration-syntax" />, while a list of
          available configuration options appears in
          <xref linkend="ch-options" />. A minimal example is shown in
          <link linkend="ex-config">Example: NixOS Configuration</link>.
        </para>
        <para>
          The command <literal>nixos-generate-config</literal> can
          generate an initial configuration file for you:
        </para>
        <programlisting>
# nixos-generate-config --root /mnt
</programlisting>
        <para>
          You should then edit
          <literal>/mnt/etc/nixos/configuration.nix</literal> to suit
          your needs:
        </para>
        <programlisting>
# nano /mnt/etc/nixos/configuration.nix
</programlisting>
        <para>
          If you’re using the graphical ISO image, other editors may be
          available (such as <literal>vim</literal>). If you have
          network access, you can also install other editors – for
          instance, you can install Emacs by running
          <literal>nix-env -f '&lt;nixpkgs&gt;' -iA emacs</literal>.
        </para>
        <variablelist>
          <varlistentry>
            <term>
              BIOS systems
            </term>
            <listitem>
              <para>
                You <emphasis>must</emphasis> set the option
                <xref linkend="opt-boot.loader.grub.device" /> to
                specify on which disk the GRUB boot loader is to be
                installed. Without it, NixOS cannot boot.
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term>
              UEFI systems
            </term>
            <listitem>
              <para>
                You <emphasis>must</emphasis> set the option
                <xref linkend="opt-boot.loader.systemd-boot.enable" />
                to <literal>true</literal>.
                <literal>nixos-generate-config</literal> should do this
                automatically for new configurations when booted in UEFI
                mode.
              </para>
              <para>
                You may want to look at the options starting with
                <link linkend="opt-boot.loader.efi.canTouchEfiVariables"><literal>boot.loader.efi</literal></link>
                and
                <link linkend="opt-boot.loader.systemd-boot.enable"><literal>boot.loader.systemd-boot</literal></link>
                as well.
              </para>
            </listitem>
          </varlistentry>
        </variablelist>
        <para>
          If there are other operating systems running on the machine
          before installing NixOS, the
          <xref linkend="opt-boot.loader.grub.useOSProber" /> option can
          be set to <literal>true</literal> to automatically add them to
          the grub menu.
        </para>
        <para>
          If you need to configure networking for your machine the
          configuration options are described in
          <xref linkend="sec-networking" />. In particular, while wifi
          is supported on the installation image, it is not enabled by
          default in the configuration generated by
          <literal>nixos-generate-config</literal>.
        </para>
        <para>
          Another critical option is <literal>fileSystems</literal>,
          specifying the file systems that need to be mounted by NixOS.
          However, you typically don’t need to set it yourself, because
          <literal>nixos-generate-config</literal> sets it automatically
          in
          <literal>/mnt/etc/nixos/hardware-configuration.nix</literal>
          from your currently mounted file systems. (The configuration
          file <literal>hardware-configuration.nix</literal> is included
          from <literal>configuration.nix</literal> and will be
          overwritten by future invocations of
          <literal>nixos-generate-config</literal>; thus, you generally
          should not modify it.) Additionally, you may want to look at
          <link xlink:href="https://github.com/NixOS/nixos-hardware">Hardware
          configuration for known-hardware</link> at this point or after
          installation.
        </para>
        <note>
          <para>
            Depending on your hardware configuration or type of file
            system, you may need to set the option
            <literal>boot.initrd.kernelModules</literal> to include the
            kernel modules that are necessary for mounting the root file
            system, otherwise the installed system will not be able to
            boot. (If this happens, boot from the installation media
            again, mount the target file system on
            <literal>/mnt</literal>, fix
            <literal>/mnt/etc/nixos/configuration.nix</literal> and
            rerun <literal>nixos-install</literal>.) In most cases,
            <literal>nixos-generate-config</literal> will figure out the
            required modules.
          </para>
        </note>
      </listitem>
      <listitem>
        <para>
          Do the installation:
        </para>
        <programlisting>
# nixos-install
</programlisting>
        <para>
          This will install your system based on the configuration you
          provided. If anything fails due to a configuration problem or
          any other issue (such as a network outage while downloading
          binaries from the NixOS binary cache), you can re-run
          <literal>nixos-install</literal> after fixing your
          <literal>configuration.nix</literal>.
        </para>
        <para>
          As the last step, <literal>nixos-install</literal> will ask
          you to set the password for the <literal>root</literal> user,
          e.g.
        </para>
        <programlisting>
setting root password...
New password: ***
Retype new password: ***
</programlisting>
        <note>
          <para>
            For unattended installations, it is possible to use
            <literal>nixos-install --no-root-passwd</literal> in order
            to disable the password prompt entirely.
          </para>
        </note>
      </listitem>
      <listitem>
        <para>
          If everything went well:
        </para>
        <programlisting>
# reboot
</programlisting>
      </listitem>
      <listitem>
        <para>
          You should now be able to boot into the installed NixOS. The
          GRUB boot menu shows a list of <emphasis>available
          configurations</emphasis> (initially just one). Every time you
          change the NixOS configuration (see
          <link linkend="sec-changing-config">Changing
          Configuration</link>), a new item is added to the menu. This
          allows you to easily roll back to a previous configuration if
          something goes wrong.
        </para>
        <para>
          You should log in and change the <literal>root</literal>
          password with <literal>passwd</literal>.
        </para>
        <para>
          You’ll probably want to create some user accounts as well,
          which can be done with <literal>useradd</literal>:
        </para>
        <programlisting>
$ useradd -c 'Eelco Dolstra' -m eelco
$ passwd eelco
</programlisting>
        <para>
          You may also want to install some software. This will be
          covered in <xref linkend="sec-package-management" />.
        </para>
      </listitem>
    </orderedlist>
  </section>
  <section xml:id="sec-installation-summary">
    <title>Installation summary</title>
    <para>
      To summarise, <link linkend="ex-install-sequence">Example:
      Commands for Installing NixOS on
      <literal>/dev/sda</literal></link> shows a typical sequence of
      commands for installing NixOS on an empty hard drive (here
      <literal>/dev/sda</literal>). <link linkend="ex-config">Example:
      NixOS Configuration</link> shows a corresponding configuration Nix
      expression.
    </para>
    <anchor xml:id="ex-partition-scheme-MBR" />
    <para>
      <emphasis role="strong">Example: Example partition schemes for
      NixOS on <literal>/dev/sda</literal> (MBR)</emphasis>
    </para>
    <programlisting>
# parted /dev/sda -- mklabel msdos
# parted /dev/sda -- mkpart primary 1MiB -8GiB
# parted /dev/sda -- mkpart primary linux-swap -8GiB 100%
</programlisting>
    <anchor xml:id="ex-partition-scheme-UEFI" />
    <para>
      <emphasis role="strong">Example: Example partition schemes for
      NixOS on <literal>/dev/sda</literal> (UEFI)</emphasis>
    </para>
    <programlisting>
# parted /dev/sda -- mklabel gpt
# parted /dev/sda -- mkpart primary 512MiB -8GiB
# parted /dev/sda -- mkpart primary linux-swap -8GiB 100%
# parted /dev/sda -- mkpart ESP fat32 1MiB 512MiB
# parted /dev/sda -- set 3 esp on
</programlisting>
    <anchor xml:id="ex-install-sequence" />
    <para>
      <emphasis role="strong">Example: Commands for Installing NixOS on
      <literal>/dev/sda</literal></emphasis>
    </para>
    <para>
      With a partitioned disk.
    </para>
    <programlisting>
# mkfs.ext4 -L nixos /dev/sda1
# mkswap -L swap /dev/sda2
# swapon /dev/sda2
# mkfs.fat -F 32 -n boot /dev/sda3        # (for UEFI systems only)
# mount /dev/disk/by-label/nixos /mnt
# mkdir -p /mnt/boot                      # (for UEFI systems only)
# mount /dev/disk/by-label/boot /mnt/boot # (for UEFI systems only)
# nixos-generate-config --root /mnt
# nano /mnt/etc/nixos/configuration.nix
# nixos-install
# reboot
</programlisting>
    <anchor xml:id="ex-config" />
    <para>
      <emphasis role="strong">Example: NixOS Configuration</emphasis>
    </para>
    <programlisting>
{ config, pkgs, ... }: {
  imports = [
    # Include the results of the hardware scan.
    ./hardware-configuration.nix
  ];

  boot.loader.grub.device = &quot;/dev/sda&quot;;   # (for BIOS systems only)
  boot.loader.systemd-boot.enable = true; # (for UEFI systems only)

  # Note: setting fileSystems is generally not
  # necessary, since nixos-generate-config figures them out
  # automatically in hardware-configuration.nix.
  #fileSystems.&quot;/&quot;.device = &quot;/dev/disk/by-label/nixos&quot;;

  # Enable the OpenSSH server.
  services.sshd.enable = true;
}
</programlisting>
  </section>
  <section xml:id="sec-installation-additional-notes">
    <title>Additional installation notes</title>
    <xi:include href="installing-usb.section.xml" />
    <xi:include href="installing-pxe.section.xml" />
    <xi:include href="installing-virtualbox-guest.section.xml" />
    <xi:include href="installing-from-other-distro.section.xml" />
    <xi:include href="installing-behind-a-proxy.section.xml" />
  </section>
</chapter>
