Install systemd-boot (x86_64)

UEFI firmware boots an EFI program from the EFI System Partition. systemd-boot is that program: it is part of systemd, already installed, and it is a menu and nothing else – no modules, no scripting, no second config language to learn.

Install it

bootctl install

That copies the EFI binary onto the ESP mounted at /boot and registers it with the firmware as a boot entry, which is the step that makes the machine choose it without being asked.

Configure the menu

default  arch.conf
timeout  3
console-mode keep
editor   no

timeout 3 gives you three seconds to interrupt; a headless machine could use 0, but a short pause is worth having the first time you boot. editor no matters more than it looks: with the editor enabled, anyone at the keyboard can append init=/bin/sh to the kernel command line and get a root shell without a password.

Write the boot entry

This is the step that tells the kernel where its root is. Generate it rather than typing the UUID by hand:

cat > /boot/loader/entries/arch.conf <<EOF
title   Arch Linux
linux   /vmlinuz-linux
initrd  /initramfs-linux.img
options root=UUID=$(findmnt -no UUID /) rootflags=subvol=@ rw
EOF
cat /boot/loader/entries/arch.conf

findmnt -no UUID / reads the UUID of the filesystem currently mounted at /, which inside the chroot is the one you are installing onto. rootflags=subvol=@ is the part specific to this book’s layout: without it the kernel mounts the top of the btrfs filesystem, finds the subvolumes sitting there as directories, and fails to boot.

If you encrypted the disk

The root device is now the unlocked mapper device, and the initramfs needs to be told which partition to unlock. Use the LUKS partition’s UUID – not the filesystem UUID above:

cat > /boot/loader/entries/arch.conf <<EOF
title   Arch Linux
linux   /vmlinuz-linux
initrd  /initramfs-linux.img
options rd.luks.name=$(blkid -s UUID -o value /dev/nvme0n1p2)=cryptroot root=/dev/mapper/cryptroot rootflags=subvol=@ rw
EOF
cat /boot/loader/entries/arch.conf

Substitute your own root partition for /dev/nvme0n1p2. The two UUIDs are easy to confuse: blkid on the partition gives the LUKS container’s UUID, while findmnt gives the UUID of the btrfs filesystem inside it.

Check it

bootctl list

It should show your entry as the default. If it reports no entries, /boot is not the ESP, and nothing you do later will make the machine boot.