Boot Process

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Boot Phases

Hardware Boot

Boot Loader

BIOS Initialization Performs first POST If all H/W connectivity is correct gives a healthy beep. Boot Strap Find s the device from where to boot :- Floppy - CDrom - Harddisk

Kernel

Init

Login Screen

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Boot Phases

Hardware Boot

Boot Loader

Active Partition Partition Information

2 Bytes 64 Bytes

Boot Loader Initialization - Grub

Kernel

Init

Stage 1

Stage 2

Sector of Stage 2

kernel - vmlinuz Initrd....img

Login Screen

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Boot Phases

Hardware Boot

Boot Loader

Kernel

Kernel initializes the devices It mounts the root file system (/) It start first process init process (/sbin/init)

Init

Login Screen

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Boot Phases

Hardware Boot

Boot Loader

Kernel

Init

Login Screen

Init reads /etc/inittab This file contains what programs or services should be run at different run levels : init init init init

0 1 2 3

init 4 init 5 init 6

shutdown single user mode multiuser mode + multiuser mode + for all services (unused) multiuser mode + Fullsupport for all restart or reboot

only text + No support for NFS only text + Full Support text mode+ GUI + services 5

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Boot Phases

Hardware Boot

Boot Loader

Kernel

Init

Login Screen

Local host login :

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To Manage Services

To Todisplay displaystatus statusof of all allservices services [root@comp1 ~]#chkconfig --list [root@comp1 ~]#chkconfig --list

To Todisplay displaystatus statusof of particular particularservice service [root@comp1 [root@comp1~]#chkconfig ~]#chkconfig --list --listnetwork network

To Tochange changeservices servicesat atcertain certainRunlevel Runlevel [root@comp1 [root@comp1~]#chkconfig ~]#chkconfig --level --level2345 2345 <service> <service>

To Tostart start//stop stopany anyservice service temporarily temporarily [root@comp1 [root@comp1~]#service ~]#service <service <servicename> name> <start/stop/restart> <start/stop/restart> 7

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