Selecting A Boot Loader; Booting With Grub - Novell LINUX ENTERPRISE SERVER 10 SP2 - INSTALLATION AND ADMINISTRATION Installation Manual

Boot Sectors
Boot sectors are the first sectors of hard disk partitions with the exception of the
extended partition, which merely serves as a "container" for other partitions. These
boot sectors have 512 bytes of space for code used to boot an operating system in-
stalled in the respective partition. This applies to boot sectors of formatted DOS,
Windows, and OS/2 partitions, which also contain some important basic data of
the file system. In contrast, the boot sectors of Linux partitions are initially empty
after setting up a file system other than XFS. Therefore, a Linux partition is not
bootable by itself, even if it contains a kernel and a valid root file system. A boot
sector with valid code for booting the system has the same magic number as the
MBR in its last two bytes (AA55).

21.1 Selecting a Boot Loader

By default, the boot loader GRUB is used in SUSE Linux Enterprise. However, in some
cases and for special hardware and software constellations, LILO may be necessary. If
you update from an older SUSE Linux Enterprise version that uses LILO, LILO is in-
stalled.
Information about the installation and configuration of LILO is available in the Support
Database under the keyword LILO and in /usr/share/doc/packages/lilo.

21.2 Booting with GRUB

GRUB (Grand Unified Bootloader) comprises two stages. stage1 consists of 512 bytes
and its only task is to load the second stage of the boot loader. Subsequently, stage2 is
loaded. This stage contains the main part of the boot loader.
In some configurations, an intermediate stage 1.5 can be used, which locates and loads
stage 2 from an appropriate file system. If possible, this method is chosen by default
on installation or when initially setting up GRUB with YaST.
stage2 is able to access many file systems. Currently, Ext2, Ext3, ReiserFS, Minix, and
the DOS FAT file system used by Windows are supported. To a certain extent, XFS,
and UFS and FFS used by BSD systems are also supported. Since version 0.95, GRUB
is also able to boot from a CD or DVD containing an ISO 9660 standard file system
pursuant to the "El Torito" specification. Even before the system is booted, GRUB can
406 Installation and Administration