1. Objectives Topic 2.6 Understanding the boot process
LPI Linux Certification
Objectives Topic 2.6
Understanding the boot process
Demonstrate your ability to change run levels, shutdown and reboot

2. Boot the system Lilo – job is to launch a linux kernel
capable of accepting information in the form of a command line
Example linux root= /dev/hda9
overrides normal boot and boots the kernel who’s label is linux on device hda and partition #9

3. Modular nature of Linux
Modules are kernel executable files produced by a C compiler for devices or process and reside in the /lib/modules/ directory – can be started before or during operation by root
Module configuration is located in /etc/conf.module
/sbin/lsmod

4. A typical etc/conf.modules
alias scsi_hostadapter aic7xxx
alias eth0 3c59x
alias parport_lowlevel parport_pc
pre-install pcmia_core /etc/rc.d/init.d/pcmcia start
alias sound op13sa2
pre-install sound insmod sound dmabuf=1
alias midi op13
options op13 io=0x530 irq=5 dma=0 dma2=1 mpu_io=0x388 io=0x370
Note alias sound is created for a audio driver opl3sa2 – you can see the I/O ports, interrupts and DMA channels

5. Note
Lilo, at boot time,can only pass kernel options on to the kernel example linux 1 for run level 1
Module options are specified in the conf.modules files

6. Kernel boot time messages
As kernel boots it sends detailed status of its progress in the form of text messages
Viewed with the dmesg command dmesg | less
Dmesg > bootmsg.txt dumps boot messages to a file for later inspection

7. Changing Run Levels Description
Halt the system quickly
1,s,S
Single user – maintance mode 2
Multi user – no nfs file sharing 3
Default – command line 4
unused 5*
Multiuser – X windows 6
Reboot system – don’t use reboot eternally
Specifies how a system is controlled by which services are running at boot time
Example linux 3
command line only

8. Changing runlevels during Operation
Init – change run levels during operation (by root)
Example – init 1 switches to single user mode – will disable others
Example – init 5 changes from text mode to X login screen

9. Linux start up scripts
/etc/rc.d
rc.sysinit – launched by init at boot time, it handles some essential chores such as mounting file systems
rc.local – file that is called upon by rc.sysinit, it contains local customizations – preferred by sys- admins to edit because it won’t be lost during a system upgrade
rc – file script that used to change between run levels
Init.d – file that controls individual start ups for services such as Apache or Mysql or Bourne shell

10. Setting the default run level
Init reads the /etc/inittab file
To determine your run level use the command runlevel - displays previous and present run level

11. Changing Runlevels with init and telinit
Init 0 = shutdown now
Init 1 = single user maintenance
Init 2 = multiuser no nfs
Init 3 = text mode (command line)
Init 5 = GUI interface starts X
Init 6 = reboot immediately Note telinit is equal to init

12. Shutdown
Shutdown command brings the system down in a secure and organized fashion
Options are on page 144
Shutdown –r now = immediately
Shutdown –r +5 System maintenance is required = shutdown in 5 mins with maintenance message
Shutdown –h 23:59 = shutdown just before midnight

13. Questions 1. Kernel options are passed on by A. By the kernel
B. By Lilo
C. I don’t know
Kernel module options are specified in which file
A. local/conf.modules
B. etc/conf.modules
C. rc.d/rc.local

14. 3. Dave has a linux system with an interrupt conflict caused by his 3c509 network card. How could Dave instruct the system to use interrupt 11 for his network adapter?
A. linux eth0=irq11 ant the lilo prompt
B. add options 3c509 irq=11 to etc/conf.modules
C. reload linux

15. 4. How do I dump my kernel boot time messages to a text file?
A. Cut and paste
B. dsmeg | less
C. dsmeg > bootmsg.txt
5. How do I change the run level to single user at boot time?
A. Init 1
B. linux 1
C. Rub 3 times and say I love you

16. I want to change my default run level at boot time to 3, which file do I edit?
A. rc.local
B. rc.sysinit
C. /etc/inittab
What command would I issue if I wanted to determine my present run level
A. runlevel
B. Init
C. Da!

17. I want to shutdown my system at noon for system maintenance, afterwards take a long lunch.
A. Shutdown –h now
B. Shutdown –r
C. Shutdown –h 12:00
What is the difference between init 0 and shutdown?
What would happen if I changed my default run level to level 6 in my /etc/inittab file?