9
The Boot Loader GRUB
This chapter describes how to congure GRUB (Grand Unied Bootloader), the boot
loader used in openSUSE®. A special YaST module is available for conguring all
settings. If you are not familiar with the subject of booting in Linux, read the following
sections to acquire some background information. This chapter also describes some of
the problems frequently encountered when booting with GRUB and their solutions.
This chapter focuses on boot management and the conguration of the boot loader
GRUB. The boot procedure as a whole is outlined in Chapter 7, Booting a Linux Sys-
tem (page 127). A boot loader represents the interface between the machine (BIOS) and
the operating system (openSUSE). The conguration of the boot loader directly impacts
the start of the operating system.
The following terms appear frequently in this chapter and might need some explanation:
MBR (Master Boot Record)
The structure of the MBR is dened by an operating system–independent conven-
tion. The rst 446 bytes are reserved for the program code. They typically hold
part of a boot loader program or an operating system selector. The next 64 bytes
provide space for a partition table of up to four entries. The partition table contains
information about the partitioning of the hard disk and the le system types. The
operating system needs this table for handling the hard disk. With conventional
generic code in the MBR, exactly one partition must be marked active. The last
two bytes of the MBR must contain a static “magic number” (AA55). An MBR
containing a different value is regarded as invalid by some BIOSes, so is not con-
sidered for booting.
The Boot Loader GRUB 155
