nixos/tests/installer: add full disk encryption test

This tests a common full disk encryption setup:
https://gist.github.com/ladinu/bfebdd90a5afd45dec811296016b2a3f

nixos/tests/installer.nix

@@ -150,8 +150,7 @@ let
           )
 
       with subtest("Shutdown system after installation"):
-          machine.succeed("umount /mnt/boot || true")
-          machine.succeed("umount /mnt")
+          machine.succeed("umount -R /mnt")
           machine.succeed("sync")
           machine.shutdown()
 
@@ -672,6 +671,55 @@ in {
     '';
   };
 
+  # Full disk encryption (root, kernel and initrd encrypted) using GRUB, GPT/UEFI,
+  # LVM-on-LUKS and a keyfile in initrd.secrets to enter the passphrase once
+  fullDiskEncryption = makeInstallerTest "fullDiskEncryption" {
+    createPartitions = ''
+      machine.succeed(
+          "flock /dev/vda parted --script /dev/vda -- mklabel gpt"
+          + " mkpart ESP fat32 1M 100MiB"  # /boot/efi
+          + " set 1 boot on"
+          + " mkpart primary ext2 1024MiB -1MiB",  # LUKS
+          "udevadm settle",
+          "modprobe dm_mod dm_crypt",
+          "dd if=/dev/random of=luks.key bs=256 count=1",
+          "echo -n supersecret | cryptsetup luksFormat -q --pbkdf-force-iterations 1000 --type luks1 /dev/vda2 -",
+          "echo -n supersecret | cryptsetup luksAddKey -q --pbkdf-force-iterations 1000 --key-file - /dev/vda2 luks.key",
+          "echo -n supersecret | cryptsetup luksOpen --key-file - /dev/vda2 crypt",
+          "pvcreate /dev/mapper/crypt",
+          "vgcreate crypt /dev/mapper/crypt",
+          "lvcreate -L 100M -n swap crypt",
+          "lvcreate -l '100%FREE' -n nixos crypt",
+          "mkfs.vfat -n efi /dev/vda1",
+          "mkfs.ext4 -L nixos /dev/crypt/nixos",
+          "mkswap -L swap /dev/crypt/swap",
+          "mount LABEL=nixos /mnt",
+          "mkdir -p /mnt/{etc/nixos,boot/efi}",
+          "mount LABEL=efi /mnt/boot/efi",
+          "swapon -L swap",
+          "mv luks.key /mnt/etc/nixos/"
+      )
+    '';
+    bootLoader = "grub";
+    grubUseEfi = true;
+    extraConfig = ''
+      boot.loader.grub.enableCryptodisk = true;
+      boot.loader.efi.efiSysMountPoint = "/boot/efi";
+
+      boot.initrd.secrets."/luks.key" = ./luks.key;
+      boot.initrd.luks.devices.crypt =
+        { device  = "/dev/vda2";
+          keyFile = "/luks.key";
+        };
+    '';
+    enableOCR = true;
+    preBootCommands = ''
+      machine.start()
+      machine.wait_for_text("Enter passphrase for")
+      machine.send_chars("supersecret\n")
+    '';
+  };
+
   swraid = makeInstallerTest "swraid" {
     createPartitions = ''
       machine.succeed(