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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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!

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?