Compaq DS10 Manual do Utilizador descarregar pdf (Página 10)

1-4 Installing Linux on Alpha Systems

1.3 How Does SRM Boot an OS?

SRM can boot from SCSI disks, floppy disks, and IDE devices.

Booting Linux with SRM is a two step process:

SRM loads and transfers control to the secondary bootstrap loader.

The secondary bootstrap loader sets up the environment for Linux, reads

the kernel image from a disk file system, and transfers control to Linux.

The secondary bootstrap loader for used for booting Linux with the SRM

firmware is aboot, which is shipped with the distributions documented in this

book.

Loading the Secondary Bootstrap Loader

SRM knows nothing about file systems or disk partitions. It expects that the

secondary bootstrap loader occupies a consecutive range of physical disk sector,

starting from a given offset. The information on the size of the secondary

bootstrap loader and the offset of its first disk sector is stored in the first 512-

byte sector. Specifically, the long integer at offset 480 stores the size of the

secondary bootstrap loader (in 512-byte blocks), and the long integer at offset

488 gives the sector number at which the secondary bootstrap loader starts. The

first sector also stores a flag-word at offset 496, which is always 0, and a

checksum at offset 504. The checksum is the sum of the first 63 long integers in

the first sector.

If the checksum in the first sector is correct, SRM reads the size sectors starting

from the sector given in the sector number field and places them in virtual

memory at address 0x20000000. If the reading completes successfully, SRM

performs a jump to address 0x20000000.

For More Information

For more information on the SRM console, see the documentation for your

Alpha system.

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Compaq DS10 Manual do Utilizador Página 10