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Objectives Topic 2.6

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

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Objectives Topic 2.6

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  1. 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 • 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?

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