What is systemd-boot

The systemd-boot utility functions as a UEFI boot manager for modern Linux systems. It displays a text menu for selecting boot entries and supports direct kernel command line editing.

Installation Prerequisites

Verify UEFI mode before installing systemd-boot. Run the following command:

$ ls /sys/firmware/efi/efivars

The directory exists when the system boots in UEFI mode. Legacy BIOS systems cannot use systemd-boot.

Installing systemd-boot

Install systemd-boot to the EFI System Partition:

# bootctl install

This command copies the boot manager files to the ESP. The UEFI firmware creates an entry named “Linux Boot Manager” in the boot order.

The installation places files at different locations based on architecture:

Architecture	File Location
x86-64	esp/EFI/systemd/systemd-bootx64.efi
x86-64 Fallback	esp/EFI/BOOT/BOOTX64.EFI
IA32	esp/EFI/systemd/systemd-bootia32.efi

XBOOTLDR Partition Setup

Create an extended boot partition to separate kernels from the ESP. This helps when dual-booting with Windows on small ESP partitions.

Set the partition type GUID to bc13c2ff-59e6-4262-a352-b275fd6f7172. Use ea00 for gdisk or xbootldr for fdisk.

The XBOOTLDR partition stores kernels and initramfs images. The ESP holds only the boot manager and configuration files.

Configuration Files

Configure the boot manager through files on the ESP. The main configuration resides in /loader/loader.conf.

Basic Configuration

Edit /loader/loader.conf to set boot behavior:

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

The default parameter specifies the boot entry filename without extension. Set timeout to the menu display duration in seconds.

Parameter	Purpose
default	Entry to boot automatically
timeout	Menu display seconds
console-mode	Screen resolution setting
editor	Enable kernel line editing

Creating Boot Entries

Place boot entry files in /loader/entries/ with the .conf extension. Each file defines one boot option.

Create an entry file:

title   Arch Linux
linux   /vmlinuz-linux
initrd  /initramfs-linux.img
options root=PARTUUID=partition-uuid rw

Replace partition-uuid with the actual partition UUID. Get the UUID with:

$ blkid -s PARTUUID -o value /dev/sdXN

Keyboard Controls

Navigate the boot menu using these keys:

Key	Action
Up/Down	Select entry
Enter	Boot selected entry
d	Set as default
e	Edit kernel parameters
+	Increase timeout
–	Decrease timeout

Press Space during boot to show the menu when timeout equals zero.

Updating systemd-boot

Update the boot manager after systemd package upgrades. Run the update command:

# bootctl update

The boot manager functions independently from the installed systemd version. Updates add new features and fix bugs.

Automatic Updates

Enable automatic updates through a systemd path unit. The system updates the boot manager when package files change.

Most distributions provide automatic update mechanisms. Check distribution documentation for specific procedures.

Boot Counting and Fallback

The boot manager tracks boot attempts automatically. Entries with counters in their filenames participate in this system.

Counter format uses two numbers separated by hyphens. The first shows remaining attempts. The second counts completed tries.

Failed entries move to the top of the menu. Working entries appear at the bottom. The default selection favors verified entries.

Working with Unified Kernel Images

Store unified kernel images in /EFI/Linux/ on the ESP. The boot manager detects these files automatically without manual entry creation.

Unified images combine kernel, initramfs, and command line into one EFI executable. This simplifies boot configuration and improves security.

EFI Variables

The boot manager communicates with the operating system through EFI variables. These variables store boot state and configuration.

Variable	Purpose
LoaderEntryDefault	Persistent default entry
LoaderEntryOneShot	Next boot entry only
LoaderConfigTimeout	Menu display duration

Use bootctl commands to modify these variables. The set-default command changes the default entry. The set-oneshot command sets a single-use override.