Systemdboot

Systemd-boot is a simple UEFI boot manager that is part of the systemd project. It was formerly known as gummiboot and is designed to provide a lightweight, straightforward boot menu for systems with UEFI firmware. It relies on the EFI System Partition (ESP) to store its bootloaders and boot entries, and it is often used as an alternative to more feature-rich boot managers such as GRUB on Linux distributions that favor a minimal setup.

Operation and structure: Systemd-boot runs in the UEFI environment and reads boot entries from the ESP. A boot configuration is organized under /loader, with a global configuration file at /loader/loader.conf and individual entries in /loader/entries/*.conf. Each entry specifies either a Linux kernel to boot or a loader binary, along with the necessary paths to the kernel, initramfs, and kernel options. Linux entries typically reference kernel and initramfs images stored on the ESP, while Windows entries point to the Windows Boot Manager. The firmware presents the menu at boot, and selection loads the chosen kernel or loader.

History, integration, and installation: The project originated as gummiboot and was renamed systemd-boot after adoption into systemd. It is maintained as part of systemd and can be installed or updated with the bootctl utility. Some distributions wire kernel-install or similar hooks to automatically create entries when a new kernel is installed, integrating with the ESP. Systemd-boot supports Secure Boot when the platform is configured accordingly.

Configuration and usage: Installing involves bootctl install to place the boot manager into the ESP. Configuration is done by creating /loader/loader.conf and /loader/entries/*.conf files. A typical entry lists title, linux, initrd, and options for Linux, or uses the loader directive to point to a Windows Boot Manager for Windows installations. The tool bootctl status can be used to verify the setup.

Notes: Systemd-boot is a minimal boot manager suited for UEFI systems; it does not support BIOS-era booting and relies on the ESP and firmware features for operation.