all: replace grub with systemd-bootsystemd-boot

Now that we use UEFI based partition, we can replace the grub with
systemd-boot.
This option have several advantages,

  - minimize installed package and dependencies
  - allow future customization (e.g. automounting, secure boot)

The pacman hook 00-systemd-boot is required to re-install the systemd
boot loader automatically when package systemd updated.

2 files changed, 30 insertions, 14 deletions

diff --git a/README.md b/README.md
index 1319dd4..1cd3923 100644
--- a/README.md
+++ b/README.md
@@ -9,7 +9,7 @@ installation, while still allowing it to be fully functional and optimized for
 Compute Engine.  Notable choices made and differences compared to a standard
 Arch Linux installation are the following:
 
-- GRUB is used with a UEFI-based boot and a GPT partition table.
+- systemd-boot is used with UEFI-based boot and a GPT partition table.
 - Serial console logging is enabled from kernel command line and journald is
   configured to forward to it.
 - Block multiqueue is configured from the kernel command line to optimize
diff --git a/build-arch-gce b/build-arch-gce
index d92bdcf..6884880 100755
--- a/build-arch-gce
+++ b/build-arch-gce
@@ -59,8 +59,8 @@ mkdir -- "$mount_dir"
 mount -- "$root_dev" "$mount_dir"
 
 echo '- Mounting the EFI partition.'
-mkdir -- "$mount_dir/efi"
-mount -- "$efi_dev" "$mount_dir/efi"
+mkdir -- "$mount_dir/boot"
+mount -- "$efi_dev" "$mount_dir/boot"
 
 echo '- Installing Arch Linux.'
 append_gce_repo() {
@@ -76,7 +76,7 @@ append_gce_repo() {
 cp /etc/pacman.conf "$work_dir"
 append_gce_repo "$work_dir/pacman.conf"
 pacstrap -G -M -C "$work_dir/pacman.conf" -- "$mount_dir" \
-	base linux grub dosfstools e2fsprogs dhclient openssh sudo google-compute-engine
+	base linux dosfstools e2fsprogs dhclient openssh sudo google-compute-engine
 append_gce_repo "$mount_dir/etc/pacman.conf"
 
 echo '- Configuring fstab.'
@@ -91,7 +91,7 @@ print_fstab() {
 } >> "$mount_dir/etc/fstab"
 {
 	print_fstab root "$root_uuid" / ext4 rw,discard,errors=remount-ro,x-systemd.growfs 0 1
-	print_fstab efi "$efi_uuid" /efi vfat uid=root,gid=root,umask=022,showexec 0 0
+	print_fstab efi "$efi_uuid" /boot vfat uid=root,gid=root,umask=022,showexec 0 0
 }
 
 echo '- Running additional setup in chroot.'
@@ -175,16 +175,32 @@ arch-chroot -- "$mount_dir" /bin/bash -s <<-'EOS'
 	rm /boot/initramfs-linux-fallback.img
 	mkinitcpio --nocolor --preset linux
 
-	echo '-- Configuring grub.'
-	grub-install --target=x86_64-efi --efi-directory=/efi --no-nvram --removable
-	cat <<-'EOF' > /etc/default/grub
-		# GRUB boot loader configuration
-		GRUB_CMDLINE_LINUX="console=ttyS0,38400n8 net.ifnames=0 scsi_mod.use_blk_mq=Y"
-		GRUB_PRELOAD_MODULES="part_gpt"
-		GRUB_TIMEOUT=0
-		GRUB_DISABLE_RECOVERY=true
+	echo '-- Running boot loader.'
+	bootctl install --no-variables --quiet
+
+	echo '-- Configuring boot loader.'
+	cat <<-'EOF' > /boot/loader/loader.conf
+		default arch.conf
+		editor no
+	EOF
+	cat <<-'EOF' > /boot/loader/entries/arch.conf
+		title   Arch Linux
+		linux   /vmlinuz-linux
+		initrd  /initramfs-linux.img
+		options rw console=ttyS0,38400n8 net.ifnames=0 scsi_mod.use_blk_mq=Y
+	EOF
+	mkdir -p -- "/etc/pacman.d/hooks"
+	cat <<-'EOF' > /etc/pacman.d/hooks/00-systemd-boot.hook
+		[Trigger]
+		Type = Package
+		Operation = Upgrade
+		Target = systemd
+
+		[Action]
+		Description = Gracefully upgrading systemd-boot...
+		When = PostTransaction
+		Exec = /usr/bin/systemctl restart systemd-boot-update.service
 	EOF
-	grub-mkconfig -o /boot/grub/grub.cfg
 EOS
 
 echo '- Cleaning up and finalizing the image.'