Grub Boot Processes

GRUB.CONG

Task  -- we can change the plash screen images help of grup file

[root@Tusharjahdav ~]# less /boot/grub/grub.conf     ------grup main files location

[root@Tusharjahdav ~]# vi /etc/grub.conf   --symlinc of grup.conf

# grub.conf generated by anaconda

#

# Note that you do not have to rerun grub after making changes to this file

# NOTICE:  You have a /boot partition.  This means that

#          all kernel and initrd paths are relative to /boot/, eg.

#          root (hd0,0)

#          kernel /vmlinuz-version ro root=/dev/sda2

#          initrd /initrd-[generic-]version.img

#boot=/dev/sda

default=0  ------------------------------------------------to select which OS you want to open default

timeout=5   --------------------------------------------------slash hold time

splashimage=(hd0,0)/grub/kcm-grub2-0.6.4.tar.gz  ----if you change this file splash image will change (image file location - /boot/grup/)

hiddenmenu

title CentOS (2.6.32-431.el6.x86_64)  -----------------OS INFO

   

 root (hd0,4)   (hd0 -----HDD)  (4 ------boot partition number (– 1)  its  means partition no is 3 )

    

   kernel /vmlinuz-2.6.32-431.el6.x86_64 ro root=UUID=c79924a2-5e11-440d-add6-522144dec58d rd_NO_LUKS rd_NO_LVM LANG=en_US.UTF-8 rd_NO_MD SYSFONT=latarcyrheb-sun16 crashkernel=auto  KEYBOARDTYPE=pc KEYTABLE=us rd_NO_DM rhgb quiet   -----red hat graphical boot quiet for graphical used

        initrd /initramfs-2.6.32-431.el6.x86_64.img

title CentOS (2.6.32-431.el6.x86_64)

        root (hd1,5)

        kernel /vmlinuz-2.6.32-431.el6.x86_64 ro root= lebel (dev/sda1) device drivers number  rd_NO_MD SYSFONT=latarcyrheb-sun16 crashkernel=auto  KEYBOARDTYPE=pc KEYTABLE=us rd_NO_DM rhgb quiet  

        initrd /initramfs-2.6.32-431.el6.x86_64.img

-------------------------------------------------------------------------------------------------------------------------

[root@Tusharjahdav ~]# ls /boot/grub/

device.map     grub.conf               menu.lst           stage2

ffs_stage1_5   kcm-grub2-0.6.4.tar.gz  stage1             xfs_stage1_5

[root@Tusharjahdav boot]# ls /boot/   --------------------To lead kernel & init

config-2.6.32-431.el6.x86_64        

initramfs-2.6.32-431.el6.x86_64.img      vmlinuz-2.6.32-431.el6.x86_64   ---kernel file

root (hd0,4)  ---(hd0 -----HDD) (4 ------boot partition number (– 1)  its  means partition no is 3 )

root= lebel (dev/sda1) device drivers number  

O – Location of the MBR

HDD  -------Hdd number

Root=lebel ---------device driver (/dev/sda1)

1        ----------------hdd partition number

Grub Boot Processes

LILO --- Has 2 stages

1) LILO 1 ----load MBR

2) LILO 2 ----bootb , map,with help of chs


GRUB -has 2 stages

1) grup ---1

2) grup ----2

3) grup ---1.5 ----------------optional stage

MBR------BIOS____MAGIC NO. CHECK_____ACTIVE PARTITON CHECK______NTLDR/GRUP LOAD ----1^st of stage of grup load will load 2nd stage of grup.

GRUP______REFER__/boot/grup/grup.conf ------according to grup.conf file it will load the kernel (vmlinz..2.6) -------------------------2^nd stage complete

#boot=/dev/sda

default=0 

timeout=5  

splashimage=(hd0,0)/grub/kcm-grub2-0.6.4.tar.gz 

hiddenmenu

title CentOS (2.6.32-431.el6.x86_64) 

   

 root (hd0,4)   (hd0 -----HDD) 

kernel /vmlinuz-2.6.32-431.el6.x86_64 ro root=UUID=c79924a2-5e11-440d-add6-522144dec58d rd_NO_LUKS rd_NO_LVM LANG=en_US.UTF-8 rd_NO_MD SYSFONT=latarcyrheb-sun16 crashkernel=auto  KEYBOARDTYPE=pc KEYTABLE=us rd_NO_DM rhgb quiet  

 initrd /initramfs-2.6.32-431.el6.x86_64.img

Grup has ext2 , ext3  file system driver ( load ) -----1.5 Stage its help to load 2^nd stage.

Grup load ext driver while installation.

#boot=/dev/sda

default=0

timeout=5

splashimage=(hd0,0)/grub/kcm-grub2-0.6.4.tar.gz

hiddenmenu

title CentOS (2.6.32-431.el6.x86_64)

        root (hd0,0)

        kernel /vmlinuz-2.6.32-431.el6.x86_64   or  root=                        rhgb quiet

        initrd /initramfs-2.6.32-431.el6.x86_64.img