nixpkgs/nixos/lib/make-disk-image.nix
obadz 24f8cf08cc nixos/lib/make-disk-image: refactor to use nixos-install
- Replace hand-rolled version of nixos-install in make-disk-image by an
  actual call to nixos-install
- Required a few cleanups of nixos-install
- nixos-install invokes an activation script which the hand-rolled version
  in make-disk-image did not do. We remove /etc/machine-id as that's
  a host-specific, impure, output of the activation script

Testing:

nix-build '<nixpkgs/nixos/release.nix>' -A tests.installer.simple passes

Also tried generating an image with:

nix-build -E 'let
    pkgs = import <nixpkgs> {};
    lib = pkgs.lib;
    nixos = import <nixpkgs/nixos> {
      configuration = {
        fileSystems."/".device = "/dev/disk/by-label/nixos";
        boot.loader.grub.devices = [ "/dev/sda" ];
        boot.loader.grub.extraEntries = '"''"'
          menuentry "Ubuntu" {
             insmod ext2
             search --set=root --label ubuntu
             configfile /boot/grub/grub.cfg
          }
        '"''"';
      };
    };
  in import <nixpkgs/nixos/lib/make-disk-image.nix> {
    inherit pkgs lib;
    config = nixos.config;
    diskSize = 2000;
    partitioned = false;
    installBootLoader = false;
  }'

Then installed the image:
$ sudo df if=./result/nixos.img of=/dev/sdaX bs=1M
$ sudo resize2fs /dev/disk/by-label/nixos
$ sudo mount /dev/disk/by-label/nixos /mnt
$ sudo mount --rbind /proc /mnt/proc
$ sudo mount --rbind /dev /mnt/dev
$ sudo chroot /mnt /nix/var/nix/profiles/system/bin/switch-to-configuration boot

[ … optionally do something about passwords … ]

and successfully rebooted to that image.

Was doing all this from inside a Ubuntu VM with a single user nix install.
2016-08-16 15:31:16 +01:00

104 lines
3 KiB
Nix

{ pkgs
, lib
, # The NixOS configuration to be installed onto the disk image.
config
, # The size of the disk, in megabytes.
diskSize
, # Whether the disk should be partitioned (with a single partition
# containing the root filesystem) or contain the root filesystem
# directly.
partitioned ? true
# Whether to invoke switch-to-configuration boot during image creation
, installBootLoader ? true
, # The root file system type.
fsType ? "ext4"
, # The initial NixOS configuration file to be copied to
# /etc/nixos/configuration.nix.
configFile ? null
, # Shell code executed after the VM has finished.
postVM ? ""
, name ? "nixos-disk-image"
, format ? "raw"
}:
with lib;
pkgs.vmTools.runInLinuxVM (
pkgs.runCommand name
{ preVM =
''
mkdir $out
diskImage=$out/nixos.${if format == "qcow2" then "qcow2" else "img"}
${pkgs.vmTools.qemu}/bin/qemu-img create -f ${format} $diskImage "${toString diskSize}M"
mv closure xchg/
'';
buildInputs = [ pkgs.utillinux pkgs.perl pkgs.e2fsprogs pkgs.parted ];
exportReferencesGraph =
[ "closure" config.system.build.toplevel ];
inherit postVM;
memSize = 1024;
}
''
${if partitioned then ''
# Create a single / partition.
parted /dev/vda mklabel msdos
parted /dev/vda -- mkpart primary ext2 1M -1s
. /sys/class/block/vda1/uevent
mknod /dev/vda1 b $MAJOR $MINOR
rootDisk=/dev/vda1
'' else ''
rootDisk=/dev/vda
''}
# Create an empty filesystem and mount it.
mkfs.${fsType} -L nixos $rootDisk
${optionalString (fsType == "ext4") ''
tune2fs -c 0 -i 0 $rootDisk
''}
mkdir /mnt
mount $rootDisk /mnt
# Register the paths in the Nix database.
printRegistration=1 perl ${pkgs.pathsFromGraph} /tmp/xchg/closure | \
${config.nix.package.out}/bin/nix-store --load-db --option build-users-group ""
# Add missing size/hash fields to the database. FIXME:
# exportReferencesGraph should provide these directly.
${config.nix.package.out}/bin/nix-store --verify --check-contents --option build-users-group ""
# In case the bootloader tries to write to /dev/sda
ln -s vda /dev/xvda
ln -s vda /dev/sda
# Install the closure onto the image
USER=root ${config.system.build.nixos-install}/bin/nixos-install \
--closure ${config.system.build.toplevel} \
--no-channel-copy \
--no-root-passwd \
${optionalString (!installBootLoader) "--no-bootloader"}
# Install a configuration.nix.
mkdir -p /mnt/etc/nixos
${optionalString (configFile != null) ''
cp ${configFile} /mnt/etc/nixos/configuration.nix
''}
# Remove /etc/machine-id so that each machine cloning this image will get its own id
rm -f /mnt/etc/machine-id
umount /mnt
# Do a fsck to make sure resize2fs works.
fsck.${fsType} -f -y $rootDisk
''
)