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388 lines
13 KiB
388 lines
13 KiB
<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" 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
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collection) can both be installed on any (most?) Linux
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distributions, they can be used to install NixOS in various creative
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ways. You can, for instance:
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</para>
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<orderedlist numeration="arabic">
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<listitem>
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<para>
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Install NixOS on another partition, from your existing Linux
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distribution (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
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existing non-NixOS Linux distribution using
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<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 numeration="arabic">
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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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<programlisting>
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$ curl -L https://nixos.org/nix/install | sh
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$ . $HOME/.nix-profile/etc/profile.d/nix.sh # …or open a fresh shell
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</programlisting>
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<para>
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More details in the
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<link xlink:href="https://nixos.org/nix/manual/#chap-quick-start">
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Nix manual</link>
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</para>
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</listitem>
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<listitem>
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<para>
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Switch to the NixOS channel:
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</para>
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<para>
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If you've just installed Nix on a non-NixOS distribution, you
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will be on the <literal>nixpkgs</literal> channel by default.
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</para>
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<programlisting>
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$ nix-channel --list
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nixpkgs https://nixos.org/channels/nixpkgs-unstable
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</programlisting>
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<para>
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As that channel gets released without running the NixOS tests,
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it will be safer to use the <literal>nixos-*</literal> channels
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instead:
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</para>
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<programlisting>
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$ nix-channel --add https://nixos.org/channels/nixos-version nixpkgs
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</programlisting>
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<para>
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You may want to throw in a
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<literal>nix-channel --update</literal> for good 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>, but this also makes some man
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pages and <literal>nixos-enter</literal> available, just in case
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you want to chroot into your NixOS partition. NixOS installs
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these by default, but you don't have NixOS yet..
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</para>
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<programlisting>
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$ nix-env -f '<nixpkgs>' -iA nixos-install-tools
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</programlisting>
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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
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partition. For installing NixOS in place using
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<literal>NIXOS_LUSTRATE</literal>, 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.
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Please refer to the partitioning, file-system creation, and
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mounting steps of <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
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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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<programlisting>
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$ sudo `which nixos-generate-config` --root /mnt
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</programlisting>
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<para>
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You'll probably want to edit the configuration files. Refer to
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the <literal>nixos-generate-config</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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Consider setting up the NixOS bootloader to give you the ability
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to boot on your existing Linux partition. For instance, if
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you're using GRUB and your existing distribution is running
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Ubuntu, you may want to add something like this to your
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<literal>configuration.nix</literal>:
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</para>
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<programlisting language="bash">
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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 "($ubuntu)/boot/grub/grub.cfg"
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}
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'';
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</programlisting>
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<para>
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(You can find the appropriate UUID for your partition in
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<literal>/dev/disk/by-uuid</literal>)
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</para>
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</listitem>
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<listitem>
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<para>
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Create the <literal>nixbld</literal> group and user on your
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original distribution:
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</para>
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<programlisting>
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$ sudo groupadd -g 30000 nixbld
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$ sudo useradd -u 30000 -g nixbld -G nixbld nixbld
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</programlisting>
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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
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boot on existing systems without the help of a rescue USB
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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
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intended only for root. In order for the installation to
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succeed, you might have to use
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<literal>PATH="$PATH:/usr/sbin:/sbin"</literal> in
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the following command.
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</para>
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</note>
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<programlisting>
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$ sudo PATH="$PATH" NIX_PATH="$NIX_PATH" `which nixos-install` --root /mnt
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</programlisting>
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<para>
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Again, please refer to the <literal>nixos-install</literal> step
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in <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
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distribution:
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</para>
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<programlisting>
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$ sudo userdel nixbld
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$ sudo groupdel nixbld
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</programlisting>
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<para>
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If you do not wish to keep the Nix package manager installed
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either, run something like
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<literal>sudo rm -rv ~/.nix-* /nix</literal> and remove the line
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that the Nix installer added to your
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<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
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using <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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<programlisting>
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$ sudo `which nixos-generate-config` --root /
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</programlisting>
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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
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<literal>nixos-generate-config</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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You'll likely want to set a root password for your first boot
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using the configuration files because you won't have a chance to
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enter a password until after you reboot. You can initalize the
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root password to an empty one with this line: (and of course
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don't forget to set one once you've rebooted or to lock the
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account with <literal>sudo passwd -l root</literal> if you use
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<literal>sudo</literal>)
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</para>
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<programlisting language="bash">
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users.users.root.initialHashedPassword = "";
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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
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<literal>system</literal> profile:
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</para>
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<programlisting>
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$ nix-env -p /nix/var/nix/profiles/system -f '<nixpkgs/nixos>' -I nixos-config=/etc/nixos/configuration.nix -iA system
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</programlisting>
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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
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(since your Nix install was probably single user):
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</para>
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<programlisting>
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$ sudo chown -R 0:0 /nix
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</programlisting>
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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
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NixOS 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
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scripts to move <emphasis>everything</emphasis> that's in the
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root partition to <literal>/old-root</literal>. This will move
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your existing distribution out of the way in the very early
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stages of the NixOS bootup. There are exceptions (we do need to
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keep NixOS there after all), so the NixOS lustrate process will
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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
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<literal>/etc/NIXOS_LUSTRATE</literal> (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
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NixOS 16.09. The act of "lustrating" refers to the
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wiping of the existing distribution. Creating
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<literal>/etc/NIXOS_LUSTRATE</literal> can also be used on
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NixOS to remove all mutable files from your root partition
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(anything that's not in <literal>/nix</literal> or
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<literal>/boot</literal> gets "lustrated" on the
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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
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other ritual 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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<programlisting>
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$ sudo touch /etc/NIXOS
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$ sudo touch /etc/NIXOS_LUSTRATE
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</programlisting>
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<para>
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Let's also make sure the NixOS configuration files are kept once
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we reboot on NixOS:
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</para>
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<programlisting>
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$ echo etc/nixos | sudo tee -a /etc/NIXOS_LUSTRATE
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</programlisting>
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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
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current distribution out of the way (the lustrate process will
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take care of the rest once you reboot, but this one must be
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moved out now because NixOS 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
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longer be bootable! If you didn't get all the NixOS
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configuration right, especially those settings pertaining to
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boot loading and root partition, NixOS may not be bootable
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either. Have a USB rescue device ready in case this happens.
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</para>
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</warning>
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<programlisting>
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$ 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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</programlisting>
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<para>
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Cross your fingers, reboot, hopefully you should get a NixOS
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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,
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you'll need to boot on a USB rescue disk and do something along
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these lines:
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</para>
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<programlisting>
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# mkdir root
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# mount /dev/sdaX root
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# mkdir root/nixos-root
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# mv -v root/* root/nixos-root/
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# mv -v root/nixos-root/old-root/* root/
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# mv -v root/boot.bak root/boot # We had renamed this by hand earlier
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# umount root
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# reboot
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</programlisting>
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<para>
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This may work as is or you might also need to reinstall the boot
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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
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old distribution:
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</para>
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<programlisting>
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sudo rm -rf /old-root
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</programlisting>
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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.
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This is especially useful for Cloud VMs, where provider do not
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provide NixOS. For instance,
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<link 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
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NixOS from 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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