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Created by: Asst. Prof. Ashish Shah, J.M.PATEL
COLLEGE, GOREGOAN W
UNIT-I
Chap- 2 BOOTING & SHUTDOWN LINUX SYSTEM
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Created by: Asst. Prof. Ashish Shah,
J.M.PATEL COLLEGE, GOREGOAN W
WHAT IS BOOTING?
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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 1ST 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.
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Created by: Asst. Prof. Ashish Shah,
J.M.PATEL COLLEGE, GOREGOAN W
LINUX BOOTING
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.
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Created by: Asst. Prof. Ashish Shah,
J.M.PATEL COLLEGE, GOREGOAN W
LINUX BOOTING: GRUB
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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.
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Created by: Asst. Prof. Ashish Shah,
J.M.PATEL COLLEGE, GOREGOAN W
GRUB STAGES
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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.
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Created by: Asst. Prof. Ashish Shah,
J.M.PATEL COLLEGE, GOREGOAN W
WHAT GRUB PROVIDES TO LINUX?
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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:IT ALLOWS MAX. FLEXIBILITY IN LOADING OS. BY
PROVIDING A TRUE COMMAND-BASED, pre-OS
ENVIRONMENT x86 MACHINES.
IT SUPPORTS LOGICAL BLOCK ADDRESSING (lba) MODE,
NEEDED TO ACCESS MANY ID AND ALL SCSI HARDDISKS.
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Created by: Asst. Prof. Ashish Shah,
J.M.PATEL COLLEGE, GOREGOAN W
LILO
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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).
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Created by: Asst. Prof. Ashish Shah,
J.M.PATEL COLLEGE, GOREGOAN W
LILO
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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-2.4.9-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).
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Created by: Asst. Prof. Ashish Shah,
J.M.PATEL COLLEGE, GOREGOAN W
LILO CONFIG FILE :
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-2.4.9-ac10
label=linux
read-only
root=/dev/hda5
append=”hdd=ide-scsi”
other=/dev/hda1
optional
label=DOS
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Created by: Asst. Prof. Ashish Shah,
J.M.PATEL COLLEGE, GOREGOAN W
BOOT STRAPING
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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.
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