First attempt at making declarative VMs

[perso/Immae/Config/Nix.git] / modules / private / system / dilion / vms / base_image.nix

diff --git a/modules/private/system/dilion/vms/base_image.nix b/modules/private/system/dilion/vms/base_image.nix
new file mode 100644 (file)
index 0000000..8de8560
--- /dev/null
+++ b/modules/private/system/dilion/vms/base_image.nix
@@ -0,0 +1,94 @@
+configuration_file: { pkgs ? import <nixpkgs> {}, system ? builtins.currentSystem, myEnv, ... }:
+let
+  config = (import <nixpkgs/nixos/lib/eval-config.nix> {
+    inherit system;
+    modules = [ {
+      myEnv = myEnv;
+      imports = [ configuration_file ];
+
+      # We want our template image to be as small as possible, but the deployed image should be able to be
+      # of any size. Hence we resize on the first boot.
+      systemd.services.resize-main-fs = {
+        wantedBy = [ "multi-user.target" ];
+        serviceConfig.Type = "oneshot";
+        script =
+          ''
+            # Resize main partition to fill whole disk
+            echo ", +" | ${pkgs.utillinux}/bin/sfdisk /dev/vda --no-reread -N 1
+            ${pkgs.parted}/bin/partprobe
+            # Resize filesystem
+            ${pkgs.e2fsprogs}/bin/resize2fs /dev/vda1
+          '';
+      };
+    } ];
+  }).config;
+in pkgs.vmTools.runInLinuxVM (
+  pkgs.runCommand "nixos-base-image"
+    {
+      memSize = 768;
+      preVM =
+        ''
+          mkdir $out
+          diskImage=image.qcow2
+          ${pkgs.vmTools.qemu}/bin/qemu-img create -f qcow2 $diskImage 2G
+          mv closure xchg/
+        '';
+      postVM =
+        ''
+          echo compressing VM image...
+          ${pkgs.vmTools.qemu}/bin/qemu-img convert -c $diskImage -O qcow2 $out/nixos.qcow2
+        '';
+      buildInputs = [ pkgs.utillinux pkgs.perl pkgs.parted pkgs.e2fsprogs ];
+      exportReferencesGraph =
+        [ "closure" config.system.build.toplevel ];
+    }
+    ''
+      # Create the partition
+      parted /dev/vda mklabel msdos
+      parted /dev/vda -- mkpart primary ext4 1M -1s
+
+      # Format the partition
+      mkfs.ext4 -L nixos /dev/vda1
+      mkdir /mnt
+      mount /dev/vda1 /mnt
+
+      for dir in dev proc sys; do
+        mkdir /mnt/$dir
+        mount --bind /$dir /mnt/$dir
+      done
+
+      storePaths=$(perl ${pkgs.pathsFromGraph} /tmp/xchg/closure)
+      echo filling Nix store...
+      mkdir -p /mnt/nix/store
+      set -f
+      cp -prd $storePaths /mnt/nix/store
+      # The permissions will be set up incorrectly if the host machine is not running NixOS
+      chown -R 0:30000 /mnt/nix/store
+
+      mkdir -p /mnt/etc/nix
+      echo 'build-users-group = ' > /mnt/etc/nix/nix.conf
+
+      # Register the paths in the Nix database.
+      export USER=root
+      printRegistration=1 perl ${pkgs.pathsFromGraph} /tmp/xchg/closure | \
+          chroot /mnt ${config.nix.package.out}/bin/nix-store --load-db
+
+      # Create the system profile to allow nixos-rebuild to work.
+      chroot /mnt ${config.nix.package.out}/bin/nix-env \
+          -p /nix/var/nix/profiles/system --set ${config.system.build.toplevel}
+
+      # `nixos-rebuild' requires an /etc/NIXOS.
+      mkdir -p /mnt/etc/nixos
+      touch /mnt/etc/NIXOS
+
+      # `switch-to-configuration' requires a /bin/sh
+      mkdir -p /mnt/bin
+      ln -s ${config.system.build.binsh}/bin/sh /mnt/bin/sh
+
+      # Generate the GRUB menu.
+      chroot /mnt ${config.system.build.toplevel}/bin/switch-to-configuration boot
+
+      umount /mnt/{proc,dev,sys}
+      umount /mnt
+    ''
+)