Bootloaders in bootc

bootc supports two ways to manage bootloaders.

bootupd

bootupd is a project explicitly designed to abstract over and manage bootloader installation and configuration. Today it primarily supports GRUB+shim. There are pending patches for it to support systemd-boot as well.

When you run bootc install, it invokes bootupctl backend install to install the bootloader to the target disk or filesystem. The specific bootloader configuration is determined by the container image and the target system's hardware.

Currently, bootc only runs bootupd during the installation process. It does not automatically run bootupctl update to update the bootloader after installation. This means that bootloader updates must be handled separately, typically by the user or an automated system update process.

systemd-boot

If bootupd is not present in the input container image, then systemd-boot will be used by default (except on s390x).

s390x

bootc uses zipl.

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