Overview of Unix System Administration

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Overview of Unix System Administration

• Bambang A.B. Sarif
• Unix System Administrator
• CCSE, KFUPM

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Agenda

• What is Unix/Linux
• What is system administration
• Things you must have
• Rules of thumb
• Good habits to develop
• In solving problems
• Automating unix system administration

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What is UNIX

• UNIX is an operating system that originated at
  Bell Labs (NJ) in 1969.
• UNIX is actually a trademark, but often used as a
  generic term to describe UNIX-like operating
  systems.
• There are numerous different flavors of UNIX
  all of which utilize similar UNIX operating
  system concepts, but may have different features
  or run on different hardware.

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The UNIX Umbrella
Hardware Vendors
Linux Distributions
Sun Solaris, HP HP-UX, Compaq True 64 UNIX, IBM
AIX, IRIX, MAC OSX
RedHat, Mandrake, SuSe, Debian, Caldera,
Yellowdog
FreeBSD, BSDI, NetBSD OpenBSD
SCO UNIX (now Caldera/Tarantula)
Other
BSD Flavors
Commercial distribution (i.e you must pay for
it)
Derivative of RedHat
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Popularity vs. Maturity
Popular
Sun Solaris
RedHat Linux / Linux Mandrake
RedHat Linux
FreeBSD / NetBSD / OpenBSD, etc.
Debian Linux
HP-UX
Caldera Linux
SuSe
AIX
Irix
Compaq True 64 UNIX
SCO UNIX
Darwin (Mac OSX)
Mature
Look for more in http//www.distrowatch.com
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What makes UNIX Unique?

• UNIX is a multi-user, time-sharing operating
  system every user gets a piece of the CPU.
• UNIX flavors generally adhere to some types of
  standards (I.e. POSIX)
• UNIX standards allow for portability of software
  across multiple UNIX distributions.

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What is Linux?

• A Unix-like operating system initially developed
  in the early 1990s by Linus Torvald.
• Initially developed to run on PC hardware but has
  been ported to other architectures as well.
• Distributed under a GNU General Public License
  free software.
• Kernel is its distinguishing feature.
• Generally packaged in various distributions.

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Linux Distributions

• Vary according to included software packages,
  package management systems, installation
  process, and Window Managers.
• Distributions
• Red Hat Enterprise Linux
• Fedora Core
• Mandriva
• Ubuntu
• OpenSuSE
• TurboLinux
• Debian GNU/Linux
• Slackware

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Why Linux?

• Linux has matured greatly over the past 5 years
  and has positioned itself as the most flexible
  UNIX distribution today.
• It can be run on very low-end, generally
  available hardware.
• Lots of software available.
• Flexible the same Linux distribution used by a
  hobbyist on low end hardware can be used by an
  enterprise on high-end hardware.
• Its the first UNIX flavor to hit retail store
  shelves and is easily obtainable across the
  world.
• Administration skill sets transfer easily to and
  from other UNIX flavors.
• Its free!

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What is system administration

• To keep, maintain and troubleshoot the system
  (unix network)
• 247 job
• Roles
• Installation and upgrade of system/applications
• Installation and upgrade services
• Manage users
• Restoring and backing up files
• Monitoring and performance tuning

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User/System Policy

• Policy has to be created before services are
  provided
• No policy means you kill yourself
• Some policies
• User account/password
• Access
• Quotas
• Services

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Things you must have

• Independent learning skill
• Analytical skills
• You dont need to know everything about unix
• There is manual page, books
• You can consult your uncle Google
• Ability to analyze the problem and look for
  solutions is more important
• Make log files your friend
• Many big problems only need a little tweaking or
  workaround
• Troubleshooting skills, troubleshooting skills,
  troubleshooting skills,
• Experience
• It can be developed
• Write it down!!

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Things you should have

• Programming/Scripting skills
• Installation new services may require you to
  compile or even debug the application
• You have to master the shell scripting skill
• Ability to understand man pages, log files
• Ability to use unix tools
• Unix provide many tools to help you in admin job
• Basic cd, ls, cat, head, tail
• Search which, locate, find
• Text cat, head, tail, grep, sed, awk, vi, emacs
• Process ps, uptime, top, sar
• Network tcpdump, snoop, netstat, ifconfig
• Disk du, df, quota, format, fsck

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Rules of Thumb

• Never restart the system unless you really have
  to.
• You can restart some services without restarting
  the system
• Dont use the graphical interface if you are a
  true admin!!!
• Most of configuration files, script, services are
  in text files
• Faster as compared to graphical interface
• You will not confused if you are managing systems
  with different unix/linux distribution

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Good habits to develop

• Write down all your experience, you may need it
  in the future
• Backup important files before you do some
  modifications.
• You can do it periodically if you want
• You can connect with more than 1 root connections
  to the system you are administering.
• In case you messed up with one connection, you
  can fix it with the other right away.

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In solving problems

• You need all information
• Username
• Hostname
• The way you connect to that hostname
• The application you were using
• The error messages
• The time when you got the error
• Can you solve the problem if a user come to you
  and just said my account is not working, Opnet
  is not working ?

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Log files

• On linux, you can go to /var/log
• Depends on the application
• Information shown in log files depend on the
  debug level you defined

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Check list

• Before you begin solving a user problem, you have
  to check few things
• Is it hardware problem
• Is it network connection problem
• Is it network problem
• Is it a specific machine problem
• Does it happen only to a specific user
• Etc

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Common User problem

• Forgot the password
• Doesnt have permission
• Doesnt have required environment variables such
  as PATH
• Mistakenly delete some files/folder
• Quota exceeded.

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Automating Unix Administration

• You dont want to spend the whole day making sure
  that all servers/workstations and its services
  are fine
• Use monitoring tools that can alert you for any
  problem in the network
• mon, nagios, cacti, angel
• Create scripts to check the status of
  servers/services and use cron to run it
  periodically
• Mail the result to admin

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Example script

• !/bin/sh
• machine"sunfire"
• down
• i0
• while i -le 15
• do
• sunmachine"i"
• /usr/sbin/ping sun gt /dev/null
• if ? -ne 0
• then
• down"downsun"
• fi
• iecho "i1" bc -l
• done
• if -n "down"
• then
• echo down tr '\012' /usr/ucb/mail -s "DOWN
  machines" admin_at_ccse.kfupm.edu.sa
• fi

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Recommended readings

• Unix system administration handbook by Evi
  Nemeth, et. all.
• Automating Unix and Linux administration by
  Bauer, Kirk

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Thank You