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