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ITI-481: Unix Administration. Meeting 2 Rutgers University Center for Applied Computer Technologies Chris Uriarte, Instructor. Today’s Agenda. Software Installation Booting and Shutting Down Emergency Boot Procedures. Software Installation. Methods of Installation Binary distributions

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iti 481 unix administration

ITI-481: Unix Administration

Meeting 2

Rutgers University Center for Applied Computer Technologies

Chris Uriarte, Instructor

ITI-481 - Chris Uriarte

today s agenda
Today’s Agenda
  • Software Installation
  • Booting and Shutting Down
  • Emergency Boot Procedures

ITI-481 - Chris Uriarte

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

ITI-481 - Chris Uriarte

red hat package manager rpm
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 many UNIX distributions managed through RPMs.
  • RPMs that are part of the Linux Distribution can be found on your install CD at:/mnt/cdrom/<Distribution Name>/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.

ITI-481 - Chris Uriarte

rpm at the command line
RPM at the Command Line
  • For a list of packages already installed:rpm –qa
  • To install a new package:rpm –ivh package-file-name
  • To upgrade an existing package:rpm –Uvh package-file-name
  • To uninstall a package: rpm –e package-name

(package name as seen in “rpm –qa”)

ITI-481 - Chris Uriarte

rpm at the command line con t
RPM at the Command Line (con’t)
  • List the files associated with a particular package:

rpm –ql package-name

ITI-481 - Chris Uriarte

package files vs installed packages
Package Files vs. Installed Packages
  • An rpm package file is a file that contains all the software associated with a particular application. It ends with the .rpm extension, for example netscape-communicator-4.71-i586.rpm
  • When the package is installed, using the rpm –i option, the package name is officially entered in the system package database as the application name and version, i.e. netscape-communicator-4.71. Therefore, to remove the package, you need use the package name – not the full name of the file that you used to install the package.

ITI-481 - Chris Uriarte

exercise using red hat package manager
Exercise: Using Red Hat Package Manager
  • Place your Linux CD in your drive - the files on your CD can now be accessed via the directory /mnt/cdrom.
  • The Mandrake/RPMS directory on your CDROM contains many RPM files.
  • Install tcpdump off of the Red Hat CD:> cd /mnt/cdrom/Mandrake/RPMS> rpm –ivh tcpdump-3.6.1-1mdk.i586.rpm
  • Uninstall elm software :> rpm -e elm-2.5.3-7mdk
  • Question: Is vim installed on your system? If so, what is the version number?

ITI-481 - Chris Uriarte

installing software from source
Installing Software from Source
  • A source installation takes 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 or RPM distribution.
  • Requires a C compiler (gcc is the most common and is pre-installed with many systems).

ITI-481 - Chris Uriarte

typical steps for installing from source
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!

ITI-481 - Chris Uriarte

exercise installing ssh1 from source
Exercise: Installing ssh1 from Source
  • Download ssh1.2.27. Additional download locations can be found at http://www.ssh.com/products/ssh/download.html.
  • From the download directory:> tar -xvzf ssh-1.2.27.tar.gz > cd ssh-1.2.27>./configure> make> make install

ITI-481 - Chris Uriarte

where to find unix software
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

ITI-481 - Chris Uriarte

where to find unix software13
Where to Find UNIX Software
  • TwoCows – http://www.twocows.com
  • SunFreeware – http://www.sunfreeware.com.
  • Download.com – http://www.download.com

ITI-481 - Chris Uriarte

when will you use these software installation procedures
When will you use these software installation procedures?
  • When you want to install a new system or user application.
  • When you need to apply patches, fixes or updates that have been provided by your OS vendor.
    • i.e. RedHat security patches and bug fixes available at: http://www.redhat.com/apps/support/errata/

ITI-481 - Chris Uriarte

the unix boot process
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 using a bootloader
    • Load the “kernel” into memory
    • Execute “rc scripts” (startup scripts)

ITI-481 - Chris Uriarte

the linux boot process
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.

ITI-481 - Chris Uriarte

linux loader lilo
Linux Loader (LILO)
  • LILO is a boot manager.
  • Usually installed in the Master Boot Record (MBR – a special segment of your hard disk that the system reads during startup).
  • 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, LILO’s purpose is to identify the location of the kernel, which is actually just a file like:/boot/vmlinuz-2.2.12-20

ITI-481 - Chris Uriarte

general unix system booting
General UNIX System Booting
  • Linux is unique, as it uses LILO - a very interactive bootloading system.
  • Administrators rarely interact with the bootloader on other flavors of UNIX (unless a special bootloader is present).
  • Other UNIX flavors, however, have capabilities that are similar to those of LILO.

ITI-481 - Chris Uriarte

the unix init process
The UNIX 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 include:0 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

ITI-481 - Chris Uriarte

unix run levels
UNIX Run Levels
  • Run Level 1 – “single user mode”
    • No prompts for username/password
    • Access only via console – no remote access to the system (i.e. telnet)
    • Very minimal services are running – no networking, no X Windows.
    • Console user has “root” permissions
    • User for system maintenance
    • Used when you forget your root password

ITI-481 - Chris Uriarte

unix run levels con t
UNIX Run Levels (con’t)
  • Run Level 2
    • All typical services are started
    • Multi-user mode – users are allowed to log into the system
    • NO NFS (Network File System) file sharing
  • Run Level 3
    • Same as run level 2, but NFS is enabled.
    • ***This is the DEFAULT system run level.

ITI-481 - Chris Uriarte

unix run levels con t22
UNIX Run Levels (con’t)
  • Run Level 4
    • Not used (historical)
  • Run Level 5
    • Same as run level 3, but the system will automatically boot into X Windows and console users will authenticate via an X Windows username/password interface.

ITI-481 - Chris Uriarte

special run levels
Special Run Levels
  • Run Level 0
    • The system “halt” or “shutdown” run level
    • System processes are stopped and the system halts
  • Run Level 6
    • The system “reboot” run level.
    • System processes are stopped and the machine is restarted.

ITI-481 - Chris Uriarte

rc scripts
rc Scripts
  • Run level scripts are located in /etc/rc.d/rcX.d (X=runlevel #, e.g. /etc/rc.d/rc3.d for run level 3). They are used for both startup and shutdown purposes.
  • These directories have startup scripts that run processes and applications during boot time. The scripts use the following naming convention:
    • K 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: start or stop. Scripts with a S are run with start option. Scripts with a K are run with a stop option.

ITI-481 - Chris Uriarte

rc scripts con t
rc scripts, con’t
  • The scripts in the rcX.d directories are typically NOT actual files themselves – they are usually symbolic links to links to scripts located in /etc/rc.d/init.d or /etc/init.d
  • For example:
    • A script that starts the apache server, might exist: /etc/rc.d/init.d/apache. This script need only contain the commands that required to start apache.
    • To start Apache during run level 3, create a symbolic link in /etc/rc.d/rc3.d called, for example, S99apache and link it to /etc/rc.d/init.d/apache

ITI-481 - Chris Uriarte

rc script example
rc script example
  • Example – you create a script that checks the system for “world writeable” files (files that anyone on the system can write to) and emails these files to you.
  • This script is called checkworldread and is located in /etc/rc.d/init.d.
  • You would like to run this script when the system starts in ANY multiuser mode (I.e. run level 2, 3 and 5)
  • Therefore, you must create rc-style symbolic links to /etc/rc.d/init.d/checkworldread from the /etc/rc.d/rc2.d, rc3.d and rc5.d directories.

ITI-481 - Chris Uriarte

rc script diagram
rc script diagram

/etc/rc.d/rc1.d

/etc/rc.d/rc3.d

/etc/rc.d/rc5.d

/etc/rc.d/rc2.d

S99checkwr

S99checkwr

S99checkwr

/etc/rc.d/init.d

Symbolic link

checkworldread

ITI-481 - Chris Uriarte

ways of changing run levels
Ways of Changing Run Levels
  • /sbin/telinit [0-6] or /sbin/init [0-6]
    • Allows you to specify a specific run level to change to
  • /sbin/shutdown (typically, “shutdown now”)
  • /sbin/reboot
  • /sbin/halt
  • At LILO boot prompt type linux <run level> (i.e. ‘linux 5’)
  • CTRL-ALT-DELETE
    • Key combination on PC-based UNIX systems reboots the systemCan be disabled in /etc/inittab.
  • ***Only power-cycle a UNIX system as a last resort.

ITI-481 - Chris Uriarte

changing the default run level
Changing the Default Run Level
  • To change the default run level, edit /etc/inittab – look for the line:

id:3:initdefault:

  • 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.
  • The default UNIX run level is 3, unless you’ve specified otherwise during setup.

ITI-481 - Chris Uriarte

useful keyboard shortcuts
Useful Keyboard Shortcuts
  • Change to text consoleCTRL-ALT-[F1-F6]
  • Change to X-Windows CTRL-ALT-F7
  • Terminate X-Session CTRL-ALT-Backspace

ITI-481 - Chris Uriarte

exercise changing runlevels
Exercise: Changing Runlevels
  • As root, type the following:shutdown –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.” (Linux only)
  • After booting into single-user mode, type:init 5

ITI-481 - Chris Uriarte

emergency boot procedures
Emergency Boot Procedures
  • If system is unable to boot normally or you forgot your root password, the following options are available:
    • Boot off of your system-specific boot disk –
      • Can be created usually be created during a UNIX install process. Linux also has a “mkbootdisk” command.
    • Boot off of your install floppy or cdrom. You may be prompted to boot into single user mode or into a “recovery mode”
    • Boot into single user mode.

ITI-481 - Chris Uriarte

homework
Homework
  • Reading Linux Administration: A Beginner’s Guide – assigned in class.

ITI-481 - Chris Uriarte