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wiki/notebook/linux.systemd.bootloader.org
Gabriel Arazas a5b3c7a8a1 Update various notes on things 
Still cannot make up a good note-taking habit especially that I archive
more than taking notes. Though, this same cannot be said for my course
notes so that's a plus.
2022-05-22 22:47:20 +08:00

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systemd-boot

systemd also comes with a bootloader aptly named systemd-boot though it only supports UEFI-based firmware. Just like GRUB, they can be configured through plain-text files.

For detailed information about the bootloader, see the manual page systemd-boot.7.

With a complete installation, the bootloader config folder may look like the following list.

/boot/
`-- loader
    |-- entries             # (ref:loader-entries)
    |   `-- arch.conf
    |-- loader.conf         # (ref:loader-conf)
    `-- random-seed
  • loader/entries/ is a directory containing all of the entries available to be booted.
  • loader.conf contains the loader configuration.

Most Linux distros with systemd installed should have a sample config file somewhere. 1 As an example, we'll show what those look like.

loader.conf is the configuration for the boot loader including the timeout seconds among others. Here is a sample of a bootloader configuration.

default arch
timeout 4

In this config, this simply makes the arch loader entry to be default when no actions has occurred. It will start loading it automatically after a timeout of 4 seconds.

The arch loader entry can be found at ${ESP}/loader/entries/arch.conf. The following code block shows what a loader entry looks like.

title   Arch Linux
linux   /vmlinuz-linux
initrd  /initramfs-linux.img
options root="PARTUUID=${PARTUUID}"

You can customize and create extra entries for the same installation. This is what NixOS does with its system generations, letting the user to boot to a specific point in time from the boot loader. Very useful for emergency boots in case the current generation breaks for whatever reason.

For complete details of the configuration file, you can see loader.conf.5 manual page.

1

In case of Arch Linux, it has an example file at /usr/share/systemd/bootctl/.