Chap- 2 BOOTING & SHUTDOWN LINUX SYSTEM Created by: Asst. Prof. Ashish Shah, J.M.PATEL COLLEGE, GOREGOAN W 1

 BOOTING REFERS TO THE PROCESS THAT STARTS OPERATING SYSTEMS WHEN THE USER TURNS ON A COMPUTER SYSTEM. WHEN COMPUTER IS BOOTED, THE BASIC IP/OP SYSTEM OR BIOS PROGRAM WILL PERFORMS SOME SYSTEM INTEGRITY CHECKS.  THE BIOS IS THE 1 ST STEP OF THE BOOT PROCESS. ONCE LOADED, THE BIOS TEST THE SYSTEM, SEARCH AND CHECK PERIPHERALS AND THEN LOCATE A VALID DEVICE WITH WHICH TO BOOT THE SYSTEM. Created by: Asst. Prof. Ashish Shah, J.M.PATEL COLLEGE, GOREGOAN W 2

 IN LINUX TWO BOOT LOADERS ARE AVIALABLE: GRUB or LILO.  GRUB IS THE DEFAULT LOADER, BUT LILO IS AVAILABLE FOR THOSE WHO REQUIRE OR PREFER IT. Created by: Asst. Prof. Ashish Shah, J.M.PATEL COLLEGE, GOREGOAN W 3

 GRUB STANDS FOR GRAND UNIFIED BOOT LOADER.  GRUB IS A PROGRAM WHICH ENABLES THE USER TO SELECT WHICH INSTALLED OS OR KERNEL TO LOAD AT SYSTEM BOOT TIME. IT ALSO ALLOWS THE USER TO CHOOSE AND EXECUTE ONE KERNEL FROM MULTIPLE KERNEL IMAGES INSTALLED ON YOUR SYSTEM AND PASS ARGUMENTS TO THE SAME.  GRUB LOADS ITSELF INTO MEMORY IN THE FOLLOWING STAGES. Created by: Asst. Prof. Ashish Shah, J.M.PATEL COLLEGE, GOREGOAN W 4

 THE STAGE1 OR PRIMARY BOOT LOADER EXISTS ON LESS THAN 512 BYTES OF DISK SPACE WITHIN THE MBR AND MERELY LOADS THE NEXT STAGE. IT IS READ INTO MEMORY BY THE BIOS FROM THE MASTER BOOT RECORD(MBR).  THE STAGE 1,5 BOOT LOADER IS ALSO QUITE SMALL. IT IS READ INTO MEMORY BY STAGE1 BOOT LOADER. THE STAGE 1,5 BOOT LOADER IS FOUND ON THE /boot/partition.  THE STAGE 2 OR SECONDARY BOOT LOADER IS READ INTO MEMORY. THE SECONDARY BOOT LOADER DISPLAYS THE GRUB MENU AND COMMAND ENVIRONMENT. THIS INTERFACE FACILITATES USER TO SELECT THE KERNEL OR OS TO BOOT. ONCE GRUB DETERMINES WHICH OS TO START, IT LOADS IT INTO MEMORY AND TRANSFERS CONTROL OF THE MACHINE TO THAT OS. IT ALSO READS initrd (RAMDISK IMAGE) INTO MEMORY.  GRUB CONFIG. FILE IS /boot/grub/grub.conf.  GRUB DISPLAYS A SPLASH SCREEN, WAITS FOR FEW SECOND, IF NO RESPONSE GOT FROM USER, IT LOADS THE DEFAULT KERNEL IMAGE AS SPECIFIED IN THE GRUB CONFIG. FILE. GRUB HAS KNOWLEDGE OF THE SYSTEM. Created by: Asst. Prof. Ashish Shah, J.M.PATEL COLLEGE, GOREGOAN W 5

 IN LINUX GRUB PROVIDES A MULTIBOOT AND MULTIDISC SYSTEM. GRUB ALLOWS YOU TO USE IT WITH ALMOST ANY OS, MOST POPULAR FILE SYSTEMS, AND ALMOST ANY HARDDISK YOUR BIOS CAN RECOGNIZE.  GRUB CONTAINS A NUMBER OF OTHER FEATURES, THE MOST IMP. OF IT ARE AS FOLLOWS:- 1. IT ALLOWS MAX. FLEXIBILITY IN LOADING OS. BY PROVIDING A TRUE COMMAND-BASED, pre-OS ENVIRONMENT x86 MACHINES. 2. IT SUPPORTS LOGICAL BLOCK ADDRESSING (lba) MODE, NEEDED TO ACCESS MANY ID AND ALL SCSI HARDDISKS. Created by: Asst. Prof. Ashish Shah, J.M.PATEL COLLEGE, GOREGOAN W 6

 LILO is the boot time LInux LOader. At boot time it gives you the option of booting into different operating systems and even into different kernel versions of the Linux operating system.  The information on where operating systems should be loaded from, and which one is started by default is stored in lilo.conf.  Whenever this file is changed, lilo must be run again in order for changes to take effect. If there is anything wrong  with the syntax of lilo.conf, lilo alerts you to that problem when you run it again.  The lilo.conf file is pretty simple. The first section  contains general information, such as which drive is the boot drive (boot=/dev/hda), and how many tenths of a second the LILO prompt should be displayed on the screen (timeout=50, which is 5 seconds).  In this lilo.conf, the operating system booted by default is linux (default=linux). Created by: Asst. Prof. Ashish Shah, J.M.PATEL COLLEGE, GOREGOAN W 7

 After the initial general preferences section you will see the boot images section. lilo.conf enables up to 16 boot images to be defined.  The first image defined here is the default linux image that boots with the vmlinuz ac10 kernel.  Its root file system is located on the first IDE disk on the fifth partition, at /dev/hda5.  The second image defined is the Windows boot partition. If you type DOS (label=DOS) at the LILO prompt, you boot into this Windows installation.  As you can see, Windows is installed on the first partition of the first IDE disk (/dev/hda1). Created by: Asst. Prof. Ashish Shah, J.M.PATEL COLLEGE, GOREGOAN W 8

Lilo.conf file is as shown below boot=/dev/hda map=/boot/map install=/boot/boot.b prompt timeout=50 message=/boot/message linear default=linux image=/boot/vmlinuz ac10 label=linux read-only root=/dev/hda5 append=”hdd=ide-scsi” other=/dev/hda1 optional label=DOS Created by: Asst. Prof. Ashish Shah, J.M.PATEL COLLEGE, GOREGOAN W 9

 In os, the term “BOOT STRAPPING” refers to the process in which a part of the os is brought into the main memory, with the processor executing it.  In a simple words, boot strapping means starting upyour computer and bringing it to a workable environment. The process “bootstrapping” is a purely dependent on the computer structural design.  When we switch on computer, many messages come up on the screen, after few seconds of system booting, we get a the login prompt. It is so because it involves entire process, from the moment we power on our computer boot strapping makes system ready for us.  During this process the internal data structures of the linux kernel are also initialized, values are set and processes are created.  The boot process involves several diff, stages that the system undertakes while it is being booted.  Failure of any of these stages may prevent the sytem to start itself. Created by: Asst. Prof. Ashish Shah, J.M.PATEL COLLEGE, GOREGOAN W 10