ITI481: Unix Administration

1
ITI-481 Unix Administration

• Meeting 2 (Parts 1 and 2)
• Meeting 3 (Part 1)

2
Todays Agenda

• Software Installation
• Booting and Shutting Down
• Emergency Boot Procedures

3
Software Installation

• Methods of Installation
• Binary distributions
• Red Hat Package Manager (RPM)
• Compiling from source
• Software installations usually must be done as
  root.

4
Red Hat Package Manager (RPM)

• Generally used for installation and removal of
  precompiled software.
• Originally deployed on Linux systems, now
  available on other major platforms (most notably,
  Solaris)
• Installation of operating system and additional
  software on Red Hat CD managed through RPMs.
• RPMs that are part of the Red Hat Distribution
  can be found on your install CD
  at/mnt/cdrom/RedHat/RPMS
• RPM installations are usually managed by the rpm
  command (/bin/rpm)
• As close to setup as you can get on UNIX one
  command installs an entire software package.

5
RPM at the Command Line

• For a list of packages already installedrpm qa
• To install a new packagerpm ivh
  package-file-name
• To upgrade an existing packagerpm Uvh
  package-file-name
• To uninstall a package rpm e package-name
• (package name as seen in rpm qa)

6
RPM at the Command Line (cont)

• List the files associated with a particular
  package
• rpm ql package-name

7
Exercise Using Red Hat Package Manager

• Place your Linux CD in your drive - the files on
  your CD can be accessed via the directory
  /mnt/cdrom.
• The RedHat/RPMS directory on your CDROM contains
  many RPM files.
• Install tcpdump off of the Red Hat CDgt cd
  /mnt/cdrom/RedHat/RPMSgt rpm ivh
  tcpdump-3.4-16.i386.rpm
• Uninstall elm software gt rpm -e elm-2.5.1-1
• Question Is pine installed on your system? If
  so, what is the version number?

8
Installing Software from Source

• A source installation the raw computer code and
  compiles it into a usable software program.
• Optimizes software for platform on which it is
  compiled.
• Generally provides more installation and
  configuration options that using a binary
  distribution.
• Requires a C compiler (gcc).

9
Typical Steps for Installing from Source

• Download source archive.
• Unpack archive
• filename.tar.gz or filename.tgz - use gzip
  and/or tar
• filename.Z use uncompress
• filename.zip use unzip
• Look at README and/or INSTALL documents for
  specific installation steps.
• Usually, you
• Run configure script if there is one.
• Run make.
• Run make install.
• Key READ the README and INSTALL files!

10
Exercise Installing ssh1 from Source

• Download ssh1.2.27. Additional download
  locations can be found at http//www.ssh.com/produ
  cts/ssh/download.html.
• From the download directorygt tar -xvzf
  ssh-1.2.27.tar.gz gt cd ssh-1.2.27gt./configuregt
  makegt make install

11
Where to Find UNIX Software

• Tucows Linuxhttp//www.linuxberg.com
• Freshmeathttp//www.freshmeat.net/
• Rpmfind.nethttp//rpmfind.net/linux/RPM/
• Updates for packages distributed with Red Hat
  Linux can be found at any of the Red Hat Mirrors
  http//www.redhat.com/download/mirror.html

12
Where to Find UNIX Software

• TwoCows http//www.twocows.com
• SunFreeware http//www.sunfreeware.com.
• Download.com http//www.download.com

13
The UNIX Boot Process

• The UNIX boot process is unique.
• UNIX is divided into system states called run
  levels, ranging from level 0 to level 6.
• UNIX Flavors boot differently, but the general
  concepts are always the same
• Bootstrap the system
• Load the kernel into memory
• Execute rc scripts (startup scripts)

14
The Linux Boot Process

• LILO starts and Linux is selected as the
  operating system to boot.
• The Linux kernel is loaded into memory and then
  probes system hardware.
• The init process reads /etc/inittab and
  determines whether runlevel 0-6 should be
  started.
• rc scripts are executed for the specified run
  level to start various services.

15
Linux Loader (LILO)

• LILO is a boot manager.
• Usually installed in the Master Boot Record (MBR
  a special segment of your hard disk).
• Configuration file is /etc/lilo.conf. If any
  changes are made to lilo.conf, /sbin/lilo needs
  to be run for the changes to become active.
• For Linux, LILOs purpose is to identify the
  location of the kernel/boot/vmlinuz-2.2.12-20

16
General UNIX System Booting

• Linux is unique, as it uses LILO is a very
  interactive bootloading system.
• Administrators rarely interact with the
  bootloader on other flavors of UNIX (unless a
  special bootloader is present).

17
The init Process

• init reads /etc/inittab, which designates what
  runlevel to start. A runlevel of initdefault is
  selected unless otherwise designated.
• A runlevel determines what functionality the
  system should be providing. Run levels
  include0 Halt the system1 Single-user (no
  networking)2 Multiuser without NFS3
  Multiuser with NFS4 Unused5 Same as 3 but
  with X11 console6 Reboot the system

18
rc Scripts

• init runs /etc/rc.d/rc.sysinit to activate swap
  partitions and check consistency of file systems.
• init runs /etc/rc.d/rc with an option designating
  the runlevel 0-6.
• Runlevel scripts are located in /etc/rc.d/rcX.d
  (Xrunlevel ). Are used for both startup and
  shutdown purposes.
• Use the following naming conventionK or S
  Number Service Name (i.e. S80sendmail)S is for
  start. K is for kill. Lower numbers start
  before higher.
• Startup scripts take two options startstop.
  Scripts with a S are run with start option.
  Scripts with a K are run with a stop option.
• Scripts in /etc/rc.d/rcX.d are symbolic links to
  /etc/rc.d/init.d.
• /etc/rc.d/rc.local runs last.

19
Ways of Changing Run Levels

• /sbin/telinit 0-6 or /sbin/init 0-6
• /sbin/shutdown h (for halt) r (for reboot)
• /sbin/reboot
• /sbin/halt
• At LILO boot promptlinux 0-6
• CTRL-ALT-DELETECan be disabled in /etc/inittab.
• Only power-cycle a Linux system as a last resort.

20
Changing the Default Run Level

• To change the default run level, edit
  /etc/inittab look for the line
• id3initdefault
• After id put the run level number you wish to
  use as your default run level. (usually 3 and 5
  are most common options)
• Now when your machine boots, it will
  automatically enter that run level.

21
Useful Keyboard Shortcuts

• Change to text consoleCTRL-ALT-F1-F6
• Change to X-Windows CTRL-ALT-F7
• Terminate X-Session CTRL-ALT-Backspace

22
Exercise Changing Runlevels

• As root, type the followingshutdown t 30 h
  System Downtime Beginning
• Hit the power switch on your machine to turn the
  system back on after the shutdown process is
  complete. NEVER turn power off without a proper
  shutdown.
• At the LILO prompt, enter linux 1. (Linus only)
• After booting into single-user mode, typeinit 5

23
Emergency Boot Procedures

• If system is unable to boot normally, the
  following options are available
• Boot off of your system-specific boot disk - Can
  be created during install process or by using
  mkbootdiskgt /sbin/mkbootdisk 2.2.12-20
• Boot into single-user mode.
• Boot off of your install floppy or cdrom.

24
Homework

• Read Chapters 5, 9, 12, and 24 in Linux
  Administration A Beginners Guide.