1. ITI-481 - Chris Uriarte ITI-481: Unix Administration Meeting 2 Rutgers University Center for Applied Computer Technologies Chris Uriarte, Instructor

2. ITI-481 - Chris Uriarte Today’s Agenda Software Installation Booting and Shutting Down Emergency Boot Procedures

3. ITI-481 - Chris Uriarte Software Installation Methods of Installation –Binary distributions –Red Hat Package Manager (RPM) –Compiling from source Software installations usually must be done as root.

4. ITI-481 - Chris Uriarte 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/ /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. ITI-481 - Chris Uriarte 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”)

6. ITI-481 - Chris Uriarte RPM at the Command Line (con’t) List the files associated with a particular package: rpm –ql package-name

7. ITI-481 - Chris Uriarte 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.

8. ITI-481 - Chris Uriarte 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?

9. ITI-481 - Chris Uriarte 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).

10. ITI-481 - Chris Uriarte 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!

11. ITI-481 - Chris Uriarte Exercise: Installing ssh1 from Source Download ssh1.2.27. Additional download locations can be found at http://www.ssh.com/products/ssh/download.html.ssh1.2.27 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

12. ITI-481 - Chris Uriarte Where to Find UNIX Software Tucows Linux http://www.linuxberg.com http://www.linuxberg.com Freshmeat http://www.freshmeat.net/ http://www.freshmeat.net/ Rpmfind.net http://rpmfind.net/linux/RPM/ http://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 http://www.redhat.com/download/mirror.html

13. ITI-481 - Chris Uriarte Where to Find UNIX Software TwoCows – http://www.twocows.comhttp://www.twocows.com SunFreeware – http://www.sunfreeware.com. http://www.sunfreeware.com Download.com – http://www.download.com http://www.download.com

14. ITI-481 - Chris Uriarte 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/ http://www.redhat.com/apps/support/errata/

15. ITI-481 - Chris Uriarte 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)

16. ITI-481 - Chris Uriarte The Linux Boot Process 1.LILO starts and Linux is selected as the operating system to boot. 2.The Linux kernel is loaded into memory and then probes system hardware. 3.The init process reads /etc/inittab and determines whether runlevel 0-6 should be started. 4.rc scripts are executed for the specified run level to start various services.

17. ITI-481 - Chris Uriarte 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

18. ITI-481 - Chris Uriarte 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.

19. ITI-481 - Chris Uriarte 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 system 1 Single-user (no networking) 2 Multiuser without NFS 3 Multiuser with NFS 4 Unused 5 Same as 3 but with X11 console 6 Reboot the system

20. ITI-481 - Chris Uriarte 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

21. ITI-481 - Chris Uriarte 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.

22. ITI-481 - Chris Uriarte 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.

23. ITI-481 - Chris Uriarte 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.

24. ITI-481 - Chris Uriarte 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.

25. ITI-481 - Chris Uriarte 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

26. ITI-481 - Chris Uriarte 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.

27. ITI-481 - Chris Uriarte rc script diagram /etc/rc.d/rc2.d /etc/rc.d/rc3.d/etc/rc.d/rc5.d/etc/rc.d/rc1.d S99checkwr /etc/rc.d/init.d checkworldread Symbolic link

28. ITI-481 - Chris Uriarte 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 (i.e. ‘linux 5’) CTRL-ALT-DELETE –Key combination on PC-based UNIX systems reboots the system Can be disabled in /etc/inittab. ***Only power-cycle a UNIX system as a last resort.

29. ITI-481 - Chris Uriarte 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.

30. ITI-481 - Chris Uriarte Useful Keyboard Shortcuts Change to text console CTRL-ALT-[F1-F6] Change to X-Windows CTRL-ALT-F7 Terminate X-Session CTRL-ALT-Backspace

31. ITI-481 - Chris Uriarte 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

32. ITI-481 - Chris Uriarte 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.

33. ITI-481 - Chris Uriarte Homework Reading Linux Administration: A Beginner’s Guide – assigned in class.