365 lines
12 KiB
XML
365 lines
12 KiB
XML
<!-- vim: set expandtab ts=2 softtabstop=2 shiftwidth=2 smarttab textwidth=80 wrapmargin=2 -->
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<section
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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-installing-from-other-distro">
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<title>Installing from another Linux distribution</title>
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<para>
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Because Nix (the package manager) & Nixpkgs (the Nix packages collection)
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can both be installed on any (most?) Linux distributions, they can be used to
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install NixOS in various creative ways. You can, for instance:
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</para>
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<orderedlist>
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<listitem>
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<para>
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Install NixOS on another partition, from your existing Linux distribution
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(without the use of a USB or optical device!)
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</para>
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</listitem>
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<listitem>
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<para>
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Install NixOS on the same partition (in place!), from your existing
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non-NixOS Linux distribution using <literal>NIXOS_LUSTRATE</literal>.
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</para>
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</listitem>
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<listitem>
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<para>
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Install NixOS on your hard drive from the Live CD of any Linux
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distribution.
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</para>
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</listitem>
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</orderedlist>
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<para>
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The first steps to all these are the same:
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</para>
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<orderedlist>
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<listitem>
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<para>
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Install the Nix package manager:
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</para>
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<para>
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Short version:
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</para>
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<screen>
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<prompt>$ </prompt>curl -L https://nixos.org/nix/install | sh
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<prompt>$ </prompt>. $HOME/.nix-profile/etc/profile.d/nix.sh # …or open a fresh shell</screen>
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<para>
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More details in the
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<link
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xlink:href="https://nixos.org/nix/manual/#chap-quick-start">
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Nix manual</link>
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</para>
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</listitem>
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<listitem>
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<para>
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Switch to the NixOS channel:
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</para>
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<para>
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If you've just installed Nix on a non-NixOS distribution, you will be on
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the <literal>nixpkgs</literal> channel by default.
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</para>
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<screen>
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<prompt>$ </prompt>nix-channel --list
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nixpkgs https://nixos.org/channels/nixpkgs-unstable</screen>
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<para>
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As that channel gets released without running the NixOS tests, it will be
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safer to use the <literal>nixos-*</literal> channels instead:
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</para>
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<screen>
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<prompt>$ </prompt>nix-channel --add https://nixos.org/channels/nixos-<replaceable>version</replaceable> nixpkgs</screen>
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<para>
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You may want to throw in a <literal>nix-channel --update</literal> for good
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measure.
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</para>
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</listitem>
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<listitem>
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<para>
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Install the NixOS installation tools:
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</para>
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<para>
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You'll need <literal>nixos-generate-config</literal> and
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<literal>nixos-install</literal> and we'll throw in some man pages and
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<literal>nixos-enter</literal> just in case you want to chroot into your
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NixOS partition. They are installed by default on NixOS, but you don't have
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NixOS yet..
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</para>
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<screen><prompt>$ </prompt>nix-env -f '<nixpkgs/nixos>' --arg configuration {} -iA config.system.build.{nixos-generate-config,nixos-install,nixos-enter,manual.manpages}</screen>
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</listitem>
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<listitem>
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<note>
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<para>
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The following 5 steps are only for installing NixOS to another partition.
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For installing NixOS in place using <literal>NIXOS_LUSTRATE</literal>,
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skip ahead.
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</para>
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</note>
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<para>
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Prepare your target partition:
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</para>
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<para>
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At this point it is time to prepare your target partition. Please refer to
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the partitioning, file-system creation, and mounting steps of
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<xref linkend="sec-installation" />
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</para>
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<para>
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If you're about to install NixOS in place using
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<literal>NIXOS_LUSTRATE</literal> there is nothing to do for this step.
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</para>
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</listitem>
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<listitem>
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<para>
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Generate your NixOS configuration:
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</para>
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<screen><prompt>$ </prompt>sudo `which nixos-generate-config` --root /mnt</screen>
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<para>
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You'll probably want to edit the configuration files. Refer to the
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<literal>nixos-generate-config</literal> step in
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<xref
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linkend="sec-installation" /> for more
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information.
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</para>
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<para>
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Consider setting up the NixOS bootloader to give you the ability to boot on
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your existing Linux partition. For instance, if you're using GRUB and your
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existing distribution is running Ubuntu, you may want to add something like
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this to your <literal>configuration.nix</literal>:
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</para>
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<programlisting>
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<xref linkend="opt-boot.loader.grub.extraEntries"/> = ''
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menuentry "Ubuntu" {
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search --set=ubuntu --fs-uuid 3cc3e652-0c1f-4800-8451-033754f68e6e
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configfile "($ubuntu)/boot/grub/grub.cfg"
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}
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'';</programlisting>
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<para>
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(You can find the appropriate UUID for your partition in
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<literal>/dev/disk/by-uuid</literal>)
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</para>
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</listitem>
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<listitem>
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<para>
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Create the <literal>nixbld</literal> group and user on your original
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distribution:
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</para>
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<screen>
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<prompt>$ </prompt>sudo groupadd -g 30000 nixbld
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<prompt>$ </prompt>sudo useradd -u 30000 -g nixbld -G nixbld nixbld</screen>
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</listitem>
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<listitem>
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<para>
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Download/build/install NixOS:
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</para>
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<warning>
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<para>
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Once you complete this step, you might no longer be able to boot on
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existing systems without the help of a rescue USB drive or similar.
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</para>
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</warning>
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<note>
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<para>
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On some distributions there are separate PATHS for programs intended only for root.
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In order for the installation to succeed, you might have to use <literal>PATH="$PATH:/usr/sbin:/sbin"</literal>
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in the following command.
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</para>
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</note>
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<screen><prompt>$ </prompt>sudo PATH="$PATH" NIX_PATH="$NIX_PATH" `which nixos-install` --root /mnt</screen>
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<para>
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Again, please refer to the <literal>nixos-install</literal> step in
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<xref linkend="sec-installation" /> for more information.
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</para>
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<para>
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That should be it for installation to another partition!
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</para>
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</listitem>
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<listitem>
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<para>
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Optionally, you may want to clean up your non-NixOS distribution:
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</para>
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<screen>
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<prompt>$ </prompt>sudo userdel nixbld
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<prompt>$ </prompt>sudo groupdel nixbld</screen>
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<para>
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If you do not wish to keep the Nix package manager installed either, run
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something like <literal>sudo rm -rv ~/.nix-* /nix</literal> and remove the
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line that the Nix installer added to your <literal>~/.profile</literal>.
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</para>
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</listitem>
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<listitem>
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<note>
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<para>
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The following steps are only for installing NixOS in place using
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<literal>NIXOS_LUSTRATE</literal>:
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</para>
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</note>
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<para>
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Generate your NixOS configuration:
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</para>
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<screen><prompt>$ </prompt>sudo `which nixos-generate-config` --root /</screen>
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<para>
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Note that this will place the generated configuration files in
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<literal>/etc/nixos</literal>. You'll probably want to edit the
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configuration files. Refer to the <literal>nixos-generate-config</literal>
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step in <xref
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linkend="sec-installation" /> for more
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information.
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</para>
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<para>
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You'll likely want to set a root password for your first boot using the
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configuration files because you won't have a chance to enter a password
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until after you reboot. You can initalize the root password to an empty one
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with this line: (and of course don't forget to set one once you've rebooted
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or to lock the account with <literal>sudo passwd -l root</literal> if you
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use <literal>sudo</literal>)
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</para>
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<programlisting>
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<link linkend="opt-users.users._name_.initialHashedPassword">users.users.root.initialHashedPassword</link> = "";
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</programlisting>
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</listitem>
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<listitem>
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<para>
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Build the NixOS closure and install it in the <literal>system</literal>
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profile:
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</para>
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<screen><prompt>$ </prompt>nix-env -p /nix/var/nix/profiles/system -f '<nixpkgs/nixos>' -I nixos-config=/etc/nixos/configuration.nix -iA system</screen>
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</listitem>
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<listitem>
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<para>
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Change ownership of the <literal>/nix</literal> tree to root (since your
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Nix install was probably single user):
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</para>
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<screen><prompt>$ </prompt>sudo chown -R 0.0 /nix</screen>
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</listitem>
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<listitem>
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<para>
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Set up the <literal>/etc/NIXOS</literal> and
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<literal>/etc/NIXOS_LUSTRATE</literal> files:
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</para>
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<para>
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<literal>/etc/NIXOS</literal> officializes that this is now a NixOS
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partition (the bootup scripts require its presence).
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</para>
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<para>
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<literal>/etc/NIXOS_LUSTRATE</literal> tells the NixOS bootup scripts to
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move <emphasis>everything</emphasis> that's in the root partition to
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<literal>/old-root</literal>. This will move your existing distribution out
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of the way in the very early stages of the NixOS bootup. There are
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exceptions (we do need to keep NixOS there after all), so the NixOS
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lustrate process will not touch:
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</para>
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<itemizedlist>
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<listitem>
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<para>
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The <literal>/nix</literal> directory
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</para>
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</listitem>
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<listitem>
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<para>
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The <literal>/boot</literal> directory
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</para>
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</listitem>
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<listitem>
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<para>
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Any file or directory listed in <literal>/etc/NIXOS_LUSTRATE</literal>
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(one per line)
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</para>
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</listitem>
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</itemizedlist>
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<note>
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<para>
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Support for <literal>NIXOS_LUSTRATE</literal> was added in NixOS 16.09.
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The act of "lustrating" refers to the wiping of the existing distribution.
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Creating <literal>/etc/NIXOS_LUSTRATE</literal> can also be used on NixOS
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to remove all mutable files from your root partition (anything that's not
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in <literal>/nix</literal> or <literal>/boot</literal> gets "lustrated" on
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the next boot.
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</para>
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<para>
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lustrate /ˈlʌstreɪt/ verb.
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</para>
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<para>
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purify by expiatory sacrifice, ceremonial washing, or some other ritual
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action.
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</para>
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</note>
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<para>
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Let's create the files:
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</para>
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<screen>
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<prompt>$ </prompt>sudo touch /etc/NIXOS
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<prompt>$ </prompt>sudo touch /etc/NIXOS_LUSTRATE
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</screen>
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<para>
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Let's also make sure the NixOS configuration files are kept once we reboot
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on NixOS:
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</para>
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<screen>
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<prompt>$ </prompt>echo etc/nixos | sudo tee -a /etc/NIXOS_LUSTRATE
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</screen>
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</listitem>
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<listitem>
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<para>
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Finally, move the <literal>/boot</literal> directory of your current
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distribution out of the way (the lustrate process will take care of the
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rest once you reboot, but this one must be moved out now because NixOS
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needs to install its own boot files:
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</para>
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<warning>
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<para>
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Once you complete this step, your current distribution will no longer be
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bootable! If you didn't get all the NixOS configuration right, especially
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those settings pertaining to boot loading and root partition, NixOS may
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not be bootable either. Have a USB rescue device ready in case this
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happens.
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</para>
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</warning>
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<screen>
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<prompt>$ </prompt>sudo mv -v /boot /boot.bak &&
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sudo /nix/var/nix/profiles/system/bin/switch-to-configuration boot
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</screen>
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<para>
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Cross your fingers, reboot, hopefully you should get a NixOS prompt!
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</para>
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</listitem>
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<listitem>
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<para>
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If for some reason you want to revert to the old distribution, you'll need
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to boot on a USB rescue disk and do something along these lines:
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</para>
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<screen>
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<prompt># </prompt>mkdir root
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<prompt># </prompt>mount /dev/sdaX root
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<prompt># </prompt>mkdir root/nixos-root
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<prompt># </prompt>mv -v root/* root/nixos-root/
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<prompt># </prompt>mv -v root/nixos-root/old-root/* root/
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<prompt># </prompt>mv -v root/boot.bak root/boot # We had renamed this by hand earlier
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<prompt># </prompt>umount root
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<prompt># </prompt>reboot</screen>
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<para>
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This may work as is or you might also need to reinstall the boot loader
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</para>
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<para>
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And of course, if you're happy with NixOS and no longer need the old
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distribution:
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</para>
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<screen>sudo rm -rf /old-root</screen>
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</listitem>
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<listitem>
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<para>
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It's also worth noting that this whole process can be automated. This is
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especially useful for Cloud VMs, where provider do not provide NixOS. For
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instance,
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<link
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xlink:href="https://github.com/elitak/nixos-infect">nixos-infect</link>
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uses the lustrate process to convert Digital Ocean droplets to NixOS from
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other distributions automatically.
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</para>
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</listitem>
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</orderedlist>
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</section>
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