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Hacking GRUB

This chapter documents the user-invisible aspect of GRUB.

As a general rule of software development, it is impossible to keep the descriptions of the internals up-to-date, and it is quite hard to document everything. So refer to the source code, whenever you are not satisfied with this documentation. Please assume that this gives just hints to you.

• Memory map: The memory map of various components
• Embedded data: Embedded variables in GRUB
• Filesystem interface: The generic interface for filesystems
• Command interface: The generic interface for built-ins
• Bootstrap tricks: The bootstrap mechanism used in GRUB
• I/O ports detection: How to probe I/O ports used by INT 13H
• Memory detection: How to detect all installed RAM
• Low-level disk I/O: INT 13H disk I/O interrupts
• MBR: The structure of Master Boot Record
• Partition table: The format of partition tables
• Submitting patches: Where and how you should send patches