nixpkgs/nixos/modules/installer/netboot/netboot.nix
David Arnold c219fdffad
nixos/installer: force root fs type
installer media can be used on top of existing host configs. In such
scenarions, root fs types will already be defined.

Before this change, this will inevitably lead to the following error:
```console
error: The option `fileSystems./.fsType' has conflicting definition values:
       - In `/nix/store/2nl5cl4mf6vnldpbxhrbzfh0n8rsv9fm-source/DevOS/os/hardware/common.nix': "ext4"
       - In `/nix/store/jbch90yqx6gg1h3fq30jjj2b6h6jfjgs-source/nixos/modules/installer/cd-dvd/iso-image.nix': "tmpfs"
```

With this patch, the installers will override those values according to
their own local requirement.

Use `mkOverride 60` so that conscientious overriding specially targeted
at the installer, e.g. with `mkForce` is still straight forward.
2021-07-28 15:05:25 -05:00

123 lines
3.5 KiB
Nix

# This module creates netboot media containing the given NixOS
# configuration.
{ config, lib, pkgs, ... }:
with lib;
{
options = {
netboot.storeContents = mkOption {
example = literalExample "[ pkgs.stdenv ]";
description = ''
This option lists additional derivations to be included in the
Nix store in the generated netboot image.
'';
};
};
config = {
# Don't build the GRUB menu builder script, since we don't need it
# here and it causes a cyclic dependency.
boot.loader.grub.enable = false;
# !!! Hack - attributes expected by other modules.
environment.systemPackages = [ pkgs.grub2_efi ]
++ (if pkgs.stdenv.hostPlatform.system == "aarch64-linux"
then []
else [ pkgs.grub2 pkgs.syslinux ]);
fileSystems."/" =
# This module is often over-layed onto an existing host config
# that defines `/`. We use mkOverride 60 to override standard
# values, but at the same time leave room for mkForce values
# targeted at the image build.
{ fsType = mkOverride 60 "tmpfs";
options = [ "mode=0755" ];
};
# In stage 1, mount a tmpfs on top of /nix/store (the squashfs
# image) to make this a live CD.
fileSystems."/nix/.ro-store" =
{ fsType = "squashfs";
device = "../nix-store.squashfs";
options = [ "loop" ];
neededForBoot = true;
};
fileSystems."/nix/.rw-store" =
{ fsType = "tmpfs";
options = [ "mode=0755" ];
neededForBoot = true;
};
fileSystems."/nix/store" =
{ fsType = "overlay";
device = "overlay";
options = [
"lowerdir=/nix/.ro-store"
"upperdir=/nix/.rw-store/store"
"workdir=/nix/.rw-store/work"
];
depends = [
"/nix/.ro-store"
"/nix/.rw-store/store"
"/nix/.rw-store/work"
];
};
boot.initrd.availableKernelModules = [ "squashfs" "overlay" ];
boot.initrd.kernelModules = [ "loop" "overlay" ];
# Closures to be copied to the Nix store, namely the init
# script and the top-level system configuration directory.
netboot.storeContents =
[ config.system.build.toplevel ];
# Create the squashfs image that contains the Nix store.
system.build.squashfsStore = pkgs.callPackage ../../../lib/make-squashfs.nix {
storeContents = config.netboot.storeContents;
};
# Create the initrd
system.build.netbootRamdisk = pkgs.makeInitrd {
inherit (config.boot.initrd) compressor;
prepend = [ "${config.system.build.initialRamdisk}/initrd" ];
contents =
[ { object = config.system.build.squashfsStore;
symlink = "/nix-store.squashfs";
}
];
};
system.build.netbootIpxeScript = pkgs.writeTextDir "netboot.ipxe" ''
#!ipxe
kernel ${pkgs.stdenv.hostPlatform.linux-kernel.target} init=${config.system.build.toplevel}/init initrd=initrd ${toString config.boot.kernelParams}
initrd initrd
boot
'';
boot.loader.timeout = 10;
boot.postBootCommands =
''
# After booting, register the contents of the Nix store
# in the Nix database in the tmpfs.
${config.nix.package}/bin/nix-store --load-db < /nix/store/nix-path-registration
# nixos-rebuild also requires a "system" profile and an
# /etc/NIXOS tag.
touch /etc/NIXOS
${config.nix.package}/bin/nix-env -p /nix/var/nix/profiles/system --set /run/current-system
'';
};
}