pyrox.dev
lol
Merge pull request #177010 from flokli/make-kexec
nixos/modules/installer/kexec/kexec-boot.nix: move into nixos/lib, expose `kexec` nixos/release.nix
authored by
Florian Klink
and committed by
GitHub
2b9be311
2de7c6f1
+201
-55
+94
nixos/doc/manual/from_md/installation/installing-kexec.section.xml
+94
nixos/doc/manual/from_md/installation/installing-kexec.section.xml
···
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<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xml:id="sec-booting-via-kexec">
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<title><quote>Booting</quote> into NixOS via kexec</title>
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<para>
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In some cases, your system might already be booted into/preinstalled
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with another Linux distribution, and booting NixOS by attaching an
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installation image is quite a manual process.
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</para>
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<para>
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This is particularly useful for (cloud) providers where you can’t
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boot a custom image, but get some Debian or Ubuntu installation.
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</para>
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<para>
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In these cases, it might be easier to use <literal>kexec</literal>
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to <quote>jump into NixOS</quote> from the running system, which
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only assumes <literal>bash</literal> and <literal>kexec</literal> to
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be installed on the machine.
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</para>
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<para>
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Note that kexec may not work correctly on some hardware, as devices
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are not fully re-initialized in the process. In practice, this
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however is rarely the case.
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</para>
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<para>
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To build the necessary files from your current version of nixpkgs,
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you can run:
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</para>
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<programlisting>
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nix-build -A kexec.x86_64-linux '<nixpkgs/nixos/release.nix>'
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</programlisting>
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<para>
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This will create a <literal>result</literal> directory containing
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the following:
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</para>
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<itemizedlist spacing="compact">
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<listitem>
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<para>
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<literal>bzImage</literal> (the Linux kernel)
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</para>
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</listitem>
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<listitem>
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<para>
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<literal>initrd</literal> (the initrd file)
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</para>
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</listitem>
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<listitem>
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<para>
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<literal>kexec-boot</literal> (a shellscript invoking
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<literal>kexec</literal>)
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</para>
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</listitem>
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</itemizedlist>
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<para>
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These three files are meant to be copied over to the other already
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running Linux Distribution.
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</para>
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<para>
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Note it’s symlinks pointing elsewhere, so <literal>cd</literal> in,
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and use <literal>scp * root@$destination</literal> to copy it over,
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rather than rsync.
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</para>
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<para>
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Once you finished copying, execute <literal>kexec-boot</literal>
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<emphasis>on the destination</emphasis>, and after some seconds, the
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machine should be booting into an (ephemeral) NixOS installation
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medium.
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</para>
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<para>
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In case you want to describe your own system closure to kexec into,
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instead of the default installer image, you can build your own
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<literal>configuration.nix</literal>:
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</para>
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<programlisting language="bash">
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{ modulesPath, ... }: {
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imports = [
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(modulesPath + "/installer/netboot/netboot-minimal.nix")
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];
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services.openssh.enable = true;
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users.users.root.openssh.authorizedKeys.keys = [
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"my-ssh-pubkey"
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];
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}
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</programlisting>
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<programlisting>
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nix-build '<nixpkgs/nixos>' \
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--arg configuration ./configuration.nix
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--attr config.system.build.kexecTree
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</programlisting>
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<para>
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Make sure your <literal>configuration.nix</literal> does still
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import <literal>netboot-minimal.nix</literal> (or
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<literal>netboot-base.nix</literal>).
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</para>
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</section>
+1
nixos/doc/manual/from_md/installation/installing.chapter.xml
+1
nixos/doc/manual/from_md/installation/installing.chapter.xml
···
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<title>Additional installation notes</title>
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<xi:include href="installing-usb.section.xml" />
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<xi:include href="installing-pxe.section.xml" />
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<xi:include href="installing-kexec.section.xml" />
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<xi:include href="installing-virtualbox-guest.section.xml" />
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<xi:include href="installing-from-other-distro.section.xml" />
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<xi:include href="installing-behind-a-proxy.section.xml" />
+64
nixos/doc/manual/installation/installing-kexec.section.md
+64
nixos/doc/manual/installation/installing-kexec.section.md
···
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# "Booting" into NixOS via kexec {#sec-booting-via-kexec}
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In some cases, your system might already be booted into/preinstalled with
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another Linux distribution, and booting NixOS by attaching an installation
5
+
image is quite a manual process.
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+
7
+
This is particularly useful for (cloud) providers where you can't boot a custom
8
+
image, but get some Debian or Ubuntu installation.
9
+
10
+
In these cases, it might be easier to use `kexec` to "jump into NixOS" from the
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+
running system, which only assumes `bash` and `kexec` to be installed on the
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+
machine.
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+
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+
Note that kexec may not work correctly on some hardware, as devices are not
15
+
fully re-initialized in the process. In practice, this however is rarely the
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+
case.
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+
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+
To build the necessary files from your current version of nixpkgs,
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+
you can run:
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+
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```ShellSession
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nix-build -A kexec.x86_64-linux '<nixpkgs/nixos/release.nix>'
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```
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+
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This will create a `result` directory containing the following:
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- `bzImage` (the Linux kernel)
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- `initrd` (the initrd file)
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- `kexec-boot` (a shellscript invoking `kexec`)
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+
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These three files are meant to be copied over to the other already running
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+
Linux Distribution.
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+
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+
Note it's symlinks pointing elsewhere, so `cd` in, and use
34
+
`scp * root@$destination` to copy it over, rather than rsync.
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+
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Once you finished copying, execute `kexec-boot` *on the destination*, and after
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+
some seconds, the machine should be booting into an (ephemeral) NixOS
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+
installation medium.
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+
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In case you want to describe your own system closure to kexec into, instead of
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the default installer image, you can build your own `configuration.nix`:
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+
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```nix
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{ modulesPath, ... }: {
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imports = [
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(modulesPath + "/installer/netboot/netboot-minimal.nix")
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];
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+
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services.openssh.enable = true;
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users.users.root.openssh.authorizedKeys.keys = [
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"my-ssh-pubkey"
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];
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}
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```
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```ShellSession
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nix-build '<nixpkgs/nixos>' \
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--arg configuration ./configuration.nix
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--attr config.system.build.kexecTree
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```
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Make sure your `configuration.nix` does still import `netboot-minimal.nix` (or
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`netboot-base.nix`).
+1
nixos/doc/manual/installation/installing.chapter.md
+1
nixos/doc/manual/installation/installing.chapter.md
···
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```{=docbook}
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<xi:include href="installing-usb.section.xml" />
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<xi:include href="installing-pxe.section.xml" />
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<xi:include href="installing-kexec.section.xml" />
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<xi:include href="installing-virtualbox-guest.section.xml" />
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<xi:include href="installing-from-other-distro.section.xml" />
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<xi:include href="installing-behind-a-proxy.section.xml" />
-51
nixos/modules/installer/kexec/kexec-boot.nix
-51
nixos/modules/installer/kexec/kexec-boot.nix
···
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# This module exposes a config.system.build.kexecBoot attribute,
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# which returns a directory with kernel, initrd and a shell script
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# running the necessary kexec commands.
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# It's meant to be scp'ed to a machine with working ssh and kexec binary
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# installed.
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# This is useful for (cloud) providers where you can't boot a custom image, but
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# get some Debian or Ubuntu installation.
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-
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{ pkgs
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, modulesPath
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, config
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, ...
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}:
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{
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imports = [
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(modulesPath + "/installer/netboot/netboot-minimal.nix")
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];
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config = {
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system.build.kexecBoot =
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let
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kexecScript = pkgs.writeScript "kexec-boot" ''
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#!/usr/bin/env bash
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if ! kexec -v >/dev/null 2>&1; then
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echo "kexec not found: please install kexec-tools" 2>&1
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exit 1
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fi
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SCRIPT_DIR=$( cd -- "$( dirname -- "''${BASH_SOURCE[0]}" )" &> /dev/null && pwd )
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kexec --load ''${SCRIPT_DIR}/bzImage \
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--initrd=''${SCRIPT_DIR}/initrd.gz \
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--command-line "init=${config.system.build.toplevel}/init ${toString config.boot.kernelParams}"
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kexec -e
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''; in
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pkgs.linkFarm "kexec-tree" [
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{
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name = "initrd.gz";
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path = "${config.system.build.netbootRamdisk}/initrd";
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}
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{
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name = "bzImage";
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path = "${config.system.build.kernel}/${config.system.boot.loader.kernelFile}";
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}
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{
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name = "kexec-boot";
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path = kexecScript;
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}
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];
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};
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}
+31
nixos/modules/installer/netboot/netboot.nix
+31
nixos/modules/installer/netboot/netboot.nix
···
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boot
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'';
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# A script invoking kexec on ./bzImage and ./initrd.gz.
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# Usually used through system.build.kexecTree, but exposed here for composability.
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system.build.kexecScript = pkgs.writeScript "kexec-boot" ''
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#!/usr/bin/env bash
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if ! kexec -v >/dev/null 2>&1; then
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echo "kexec not found: please install kexec-tools" 2>&1
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exit 1
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fi
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SCRIPT_DIR=$( cd -- "$( dirname -- "''${BASH_SOURCE[0]}" )" &> /dev/null && pwd )
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kexec --load ''${SCRIPT_DIR}/bzImage \
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--initrd=''${SCRIPT_DIR}/initrd.gz \
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--command-line "init=${config.system.build.toplevel}/init ${toString config.boot.kernelParams}"
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kexec -e
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'';
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# A tree containing initrd.gz, bzImage and a kexec-boot script.
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system.build.kexecTree = pkgs.linkFarm "kexec-tree" [
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{
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name = "initrd.gz";
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path = "${config.system.build.netbootRamdisk}/initrd";
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}
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{
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name = "bzImage";
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path = "${config.system.build.kernel}/${config.system.boot.loader.kernelFile}";
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}
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{
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name = "kexec-boot";
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path = config.system.build.kexecScript;
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}
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];
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boot.loader.timeout = 10;
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boot.postBootCommands =
+7
nixos/release.nix
+7
nixos/release.nix
···
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# Build the initial ramdisk so Hydra can keep track of its size over time.
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initialRamdisk = buildFromConfig ({ ... }: { }) (config: config.system.build.initialRamdisk);
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kexec = forMatchingSystems supportedSystems (system: (import lib/eval-config.nix {
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inherit system;
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modules = [
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./modules/installer/netboot/netboot-minimal.nix
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];
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}).config.system.build.kexecTree);
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+
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netboot = forMatchingSystems supportedSystems (system: makeNetboot {
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module = ./modules/installer/netboot/netboot-minimal.nix;
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inherit system;
+3
-4
nixos/tests/kexec.nix
+3
-4
nixos/tests/kexec.nix
···
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virtualisation.vlans = [ ];
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environment.systemPackages = [ pkgs.hello ];
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imports = [
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"${modulesPath}/installer/kexec/kexec-boot.nix"
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"${modulesPath}/profiles/minimal.nix"
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"${modulesPath}/installer/netboot/netboot-minimal.nix"
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];
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};
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};
···
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node1.connect()
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node1.wait_for_unit("multi-user.target")
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# Check if the machine with kexec-boot.nix profile boots up
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# Check if the machine with netboot-minimal.nix profile boots up
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node2.wait_for_unit("multi-user.target")
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node2.shutdown()
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# Kexec node1 to the toplevel of node2 via the kexec-boot script
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node1.succeed('touch /run/foo')
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node1.fail('hello')
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node1.execute('${nodes.node2.config.system.build.kexecBoot}/kexec-boot', check_return=False)
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node1.execute('${nodes.node2.config.system.build.kexecTree}/kexec-boot', check_return=False)
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node1.succeed('! test -e /run/foo')
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node1.succeed('hello')
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node1.succeed('[ "$(hostname)" = "node2" ]')