YaST - The Bootloader Module

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Goal

This module has two main responsibilities:

  1. Proposing a bootable configuration so even beginners who've never heard about booting can get a bootable distribution out of the box without any interaction.

  2. Letting advanced users who already know what they want to achieve to edit an existing configuration or a proposal.

Check our list of supported scenarios.

Development

High Level Overview

The bootloader module consists of two more or less separated components. The UI including dialogs, widgets and similar, and the backend that is responsible for reading, writing, proposing.

Backend

overview picture

To get to the clickable links in the image, right-click the diagram and choose "Display Image" (Firefox) or "Open Image in New Tab" (Chromium).

The entry point to the backend is the bootloader factory, that holds and also can propose the bootloader implementation. So now let's explain each component of the picture:

  • GRUB2 for legacy booting or emulated grub2 boot like s390x.
  • GRUB2-EFI for EFI variant of GRUB2 bootloader
  • None when YaST does not manage booting
  • GRUB2 base is the shared functionality for both GRUB2 implementations
  • GRUB password is a specific class that manages password protection of grub2
  • Sections is a component responsible for getting info about generated grub2 sections and what the default section for booting is
  • GRUB2 install is responsible for calling the grub2-install script with correct arguments. For legacy booting it gets target stage1 devices.
  • Device Map is a component responsible for managing the mapping between grub device names and kernel/udev names.
  • Stage1 holds information about stage1 location for grub2, also whether a generic MBR is needed and whether a partition should be activated.
  • MBR Update is responsible for generic MBR and stage1 if needed
  • Boot Record backup creates a backup of boot record for devices which the code touched
  • Serial Console converts between grub2 serial console configuration and kernel serial console configuration
  • Sysconfig read/write sysconfig configuration for bootloader. Sysconfig basically holds currently used grub2 implementation and configuration that is not in grub2 itself like if use secure boot or trusted grub

See Also

The bootloader module uses CFA (config files API) module for GRUB2 - See CFA for GRUB2 repository