UEFI support

Author: Rotsor

.gitignore

@@ -2,3 +2,4 @@
 /latest-iso-minimal-x86_64-linux
 /latest-iso-graphical-x86_64-linux
 /nixos-in-place-test
+*.iso

README.md

@@ -29,10 +29,14 @@ old system and all your old files still exist and are setup to mount on
 `/old-root/nixos` and `/` is rebound before spinning up the system; everything
 else in `/old-root` is fair game to delete.
 
-NixOS installs GRUB2 on top of your existing boot loader. If you'd like to boot
-into `/old-root`, you can; you just need to add the GRUB entry, from
+If your system boots using MBR, NixOS installs GRUB2 on top of your existing boot loader.
+If you'd like to boot into `/old-root`, you can; you just need to add the GRUB entry, from
 `/old-root/boot/grub`, manually in your Nix files.
 
+If your system boots using UEFI, NixOS adds systemd-boot efi image to your
+efi system partition, so your bios should let you choose between your old efi
+image and systemd-boot.
+
 ## Platform-specifics
 ### Digital Ocean
 For use on DO droplets, follow the normal steps for your platform (Debian has

install

@@ -18,19 +18,46 @@ check_existence "grep"
 check_existence "unsquashfs"
 check_existence "mktemp"
 check_existence "id"
+check_existence "head"
+check_existence "tail"
+check_existence "fdisk"
+check_existence "cat"
 log_end "seems sane"
 
 ## Setup essential variables; allow overriding with input
 root_mount=$(mount | grep "/ " | sed 's/ /\n/' | head -n1)
 root_type=$(mount | grep -Eo "/ type \w+" | sed 's/ /\n/g' | tail -n1)
-if grep '/dev/nvme' <<< $root_mount; then
-  grub_device=$(echo $root_mount | sed "s|p[0-9]\+$||");
-elif grep '/dev/sd' <<< $root_mount; then
-  grub_device=$(echo $root_mount | sed "s|[0-9]\+||");
-elif grep '/dev/vd' <<< $root_mount; then
-  grub_device=$(echo $root_mount | sed "s|[0-9]\+||");
+
+expect_one_line() {
+  ERROR_MESSAGE_ZERO=$1
+  ERROR_MESSAGE_MULTIPLE=$2
+  (set -eu;
+   IFS='' read -r x || (echo "$ERROR_MESSAGE_ZERO" >& 2; exit 1)
+   (! IFS='' read -r) || (echo "$ERROR_MESSAGE_MULTIPLE" >& 2; exit 1)
+   printf "%s\n" "$x");
+}
+
+if [ -d /sys/firmware/efi ]; then
+  boot_type=uefi
+  boot_device=$(
+    set -euo pipefail
+    fdisk -l -o 'Device,Type' |
+      grep 'EFI System' |
+      sed -r 's_([^ ]*) *EFI System$_\1_' |
+      expect_one_line \
+	"Fdisk found no EFI System Partitions: please specify with -g option" \
+	"Found multiple EFI System Partitions: please specify with -g option")
 else
-  echo "Unable to determine your grub boot device! Please specify with the -g option."
+  boot_type=mbr
+  if grep '/dev/nvme' <<< "$root_mount"; then
+    boot_device=$(echo "$root_mount" | sed "s|p[0-9]\+$||");
+  elif grep '/dev/sd' <<< "$root_mount"; then
+    boot_device=$(echo "$root_mount" | sed "s|[0-9]\+||");
+  elif grep '/dev/vd' <<< "$root_mount"; then
+    boot_device=$(echo "$root_mount" | sed "s|[0-9]\+||");
+  else
+    echo "Unable to determine your grub boot device! Please specify with the -g option."
+  fi
 fi
 working_directory=$(mktemp -d)
 
@@ -48,7 +75,7 @@ digitalocean=false
 while getopts ":g:r:t:Gdw:h" opt; do
   case $opt in
     g)
-      grub_device=$OPTARG
+      boot_device=$OPTARG
       ;;
     r)
       root_mount=$OPTARG
@@ -100,9 +127,22 @@ then
   fi
 fi
 
+boot_description=$(
+  case $boot_type in
+    uefi)
+      echo "uefi boot with esp at $boot_device"
+      ;;
+    mbr)
+      echo "mbr at $boot_device"
+      ;;
+    *)
+      echo "bad boot type" >&2
+      exit 1
+      ;;
+  esac)
 ## Give one last chance to back out
 log "NixOS installer (nixos-in-place)"
-log "   GRUB => $grub_device"
+log "   Boot => $boot_description"
 log "   Root => $root_mount ($root_type)"
 log "   ISO => $iso"
 log "   Digital Ocean => $digitalocean"
@@ -134,7 +174,7 @@ pushd "$working_directory"
 
   ## Setup the chroot environment before install
   log "Embarking stage1!"
-  "$here/stage1" "$here" "$root_mount" "$root_type" "$grub_device" "$digitalocean"
+  "$here/stage1" "$here" "$root_mount" "$root_type" "$boot_type" "$boot_device" "$digitalocean"
 
   ## Minimize residual space usage
   # /var/empty is immutable https://github.com/NixOS/nixpkgs/pull/18365

stage1

@@ -5,8 +5,9 @@ set -eu
 here=$1
 root_mount=$2
 root_type=$3
-grub_device=$4
-digitalocean=$5
+boot_type=$4
+boot_device=$5
+digitalocean=$6
 
 ## Bring in some helper functions
 . "$here/util"
@@ -28,7 +29,7 @@ log_end "$BASH"
 
 ## Don't run systemd on chroot start, run our stage2 script
 log "Patching init"
-sed -i "s,exec systemd,exec /$BASH -i /nixos-in-place/stage2 $root_mount $root_type $grub_device $digitalocean," "$INIT"
+sed -i "s,exec systemd,exec /$BASH -i /nixos-in-place/stage2 $root_mount $root_type $boot_type $boot_device $digitalocean," "$INIT"
 sed -i "s,starting systemd,starting /nixos-in-place/stage2," "$INIT"
 
 ## Don't try to remount / since we didn't do a proper phase 1
@@ -43,12 +44,27 @@ mount --bind /nixos nixos
 mkdir -p nixos-in-place
 mount --bind "$here" nixos-in-place
 
+case "$boot_type" in
+  mbr)
+    true
+    ;;
+  uefi)
+    (ls -1 /sys/firmware/efi/efivars | grep -q .) || mount -t efivarfs efivarfs /sys/firmware/efi/efivars
+    mkdir -p nixos/boot
+    mount "$boot_device" nixos/boot
+    ;;
+  *)
+    echo "bad boot type" >&2
+    exit 1
+esac
+
 ## Imbue the modified live CD environment so we can install
 log "Embarking stage2!"
 chroot . "/$INIT"
 
 ## Various platforms use different flags; just try what we can to clean up
 log "Cleaning up mounts"
+umount -f nixos/boot >/dev/null 2>&1 || true
 umount -fR nixos >/dev/null 2>&1 || true
 umount -f nixos >/dev/null 2>&1 || true
 umount -f nixos-in-place >/dev/null 2>&1 || true

stage2

@@ -4,8 +4,9 @@ set -eu
 
 root_mount=$1
 root_type=$2
-grub_device=$3
-digitalocean=$4
+boot_type=$3
+boot_device=$4
+digitalocean=$5
 digitalocean_configs=""
 
 if [ "$digitalocean" = "true" ];
@@ -47,12 +48,26 @@ nix-env -i pcre
 ## Generate a base config
 nixos-generate-config --root /nixos
 
+grub_device_config=$(
+  case "$boot_type" in
+    mbr)
+      echo "boot.loader.grub.device = \"$boot_device\";\n"
+      ;;
+    uefi)
+      true
+      ;;
+    *)
+      echo "bad boot type" >&2
+      exit 1
+      ;;
+  esac)
+
 cat <<EOF > /nixos/etc/nixos/nixos-in-place.nix
 { config, pkgs, ... }:
 {
   ## Everything below is generated from nixos-in-place; modify with caution!
   boot.kernelParams = ["boot.shell_on_fail"];
-  boot.loader.grub.device = "$grub_device";
+  $grub_device_config
   boot.loader.grub.storePath = "/nixos/nix/store";
   boot.initrd.supportedFilesystems = [ "$root_type" ];
   boot.initrd.postDeviceCommands = ''

util

@@ -20,7 +20,7 @@ show_help()
   log "usage: $0 [OPTION...]"
   log
   log "  -h         Show this help message"
-  log "  -g <dev>   Set GRUB target device (default: ${grub_device:-undefined})"
+  log "  -g <dev>   Set boot device (a device with MBR or EFI System Partition) (default: ${boot_device:-undefined})"
   log "  -r <dev>   Set root filesystem target device (default: ${root_mount:-undefined})"
   log "  -t <type>  Set root filesystem type (default: ${root_type:-undefined})"
   log "  -G         Use the graphical NixOS ISO (default: ${iso:-undefined})"