1. Introduction & Background of Network and
System Administration
1
Chapter one

2. 1.1 Computer Systems & Network
overview
2
What is a Computer Network
Network: a system containing any combination of
computers, computer terminals, printers, audio or visual
display devices, or telephones interconnected by
telecommunication equipment or cables: used to transmit
or receive information.

3. The Network Diagram
(
3
The Internet
Other LANS
Firewall
Router
Fiber Optic Network Cable
Server
PC
Wireless Network
Wired Network
Switch

4. Types of Networks
4
WIDE AREA LOCAL AREA

5. Wide Area Network
5
• A Wide Area Network exist over a large area
• Data travels through telephone or cable lines
• Usually requires a Modem
• The world’s largest Wide Area Network is the Internet

6. Local Area Network
6
• A Local Area Network spans a relatively small area
• LAN are usually confined to one building or a group of buildings
• Data travel between network devices via network cables.
• The most common type of Local Area Network is called Ethernet

7. Peer to Peer Network
7
• Usually very small networks
• Each workstation has equivalent capabilities and responsibilities
• Does not require a switch or a hub.
• These types of networks do not perform well under heavy data
loads.

8. Switches and Hubs
8
• Data travels faster through switches because data is not sequenced as it
is in a hub
• The information is more secure when it passes through a switch as
opposed to a hub.
• Information travels more efficiently through a switch because travels
directly to it’s destination as opposed to being broadcast to all PC’s on
the network hub.
Network Switches Network Hubs

9. Servers
9
Users are connected to certain servers
which will fulfill the required request.
There are 3 Principle Types of Servers
Print Servers
Contains the name and location of all
printers that are on the Network
File Servers
Contain the location and names of the
various drives, files, and folders on a
Network
Web Servers
Contain the Programs, Files, and Internet
Web Sites
Rack of Servers

10. Definition of system administrator
10
 General definition of system administrator :
“one who manages computer and network systems
on behalf of another, such as an employer or a
client”.
 SAs are the people who make things work and keep
it all running.
 SA looks after computers, networks, and the
people who use them.
 SA may look after hardware, operating systems,
software, configurations, applications, or security.

11. 1.2 Philosophy of System Administration
11
 System administration guidelines which make up the philosophy of
system administration are:
 Automate everything
 Document everything
 Communicate as much as possible
 Know your resources
 Know your users
 Know your business
 Secure the system
 Plan ahead
 Expect the unexpected

12. 1.2.1 Automate everything
12
 Anything done more than once should be
examined as a possible candidate for automation.
 Here are some commonly automated tasks:
 Free disk space checking and reporting
 Backups
 System performance data collection
 User account maintenance (creation, deletion, etc.)
 Business-specific functions (pushing new data to a
Web server, running monthly/quarterly/yearly
reports, etc.)

13. Cont..
13
 Note:
 “Keep in mind that if you have a task that should be
automated, it is likely that you are not the first system
administrator to have that need. Here is where the benefits of
open source software really shine -- you may be able to
leverage someone else's work to automate the manual
procedure that is currently consuming your time. So always
make sure you search the Web before writing anything more
complex than a small Perl script.”

14. 1.2.2. Document everything
14
 What should you document? Here is a partial list:
 Policies
 Policies are written to formalize and clarify the
relationship system and network admin has with user
community. They make it clear to your users how their
requests for resources and/or assistance are handled.
The nature, style, and method of disseminating policies
to your a community varies from organization to
organization.
 Procedures
 Procedures are any step-by-step sequence of actions
that must be taken to accomplish a certain task.
Procedures to be documented can include backup
procedures, user account management procedures,
problem reporting procedures, and so on. Like
automation, if a procedure is followed more than once, it
is a good idea to document it.

15. Cont. ..
15
 Changes
 A large part of a system administrator's career revolves
around making changes -- configuring systems for
maximum performance, tweaking scripts, modifying
configuration files, and so on. All of these changes
should be documented in some fashion.

16. 1.2.3 Communicate as much as
possible
16
 The method by which you communicate with your users
can vary according to your organization. Some
organizations use email; others, an internal website.
 Tell your users what you are going to do
 Tell your users what you are doing
 Tell your users what you have done

17. 1.2.4. Know your Resource, Business and
Users
17
 System administration is mostly a matter of
balancing available resources against the people
and programs that use those resources.
 Some of the resources are:
 System resources, such as available processing power,
memory, and disk space
 Network bandwidth
 Available money in the IT budget
 Whether system admin work for a large, multinational
corporation or a small community college, It important to
understand the nature of the business environment and
users of a system.

18. 1.2.5. Secure organization systems and
network
18
 No matter what you might think about the environment in
which your systems are running, you cannot take security
for granted. Even standalone systems not connected to the
Internet may be at risk (although obviously the risks will be
different from a system that has connections to the outside
world).
 Therefore, it is extremely important to consider the security
implications of everything you do.

19. Cont. ..: (Secure the systems)
19
 While you are thinking about security, do not make the
mistake of assuming that possible intruders will only attack
your systems from outside of your company. Many times
the perpetrator is someone within the company. So the
next time you walk around the office, look at the people
around you and ask yourself this question:
 What would happen if that person were to attempt to
subvert our security?

20. 1.2.6. Plan ahead and Expect
unexpected
20
 Certainly no one can predict the future with 100%
accuracy. However, with a bit of awareness it is easy
to read the signs of many changes:
 Signs of system failure
 Signs of network failure
 Requirement of scalability
 Further security and remote administration requirements
 Being able to read signs (and responding effectively
to them) makes life easier for system administrators
and users.

21. 2.3 Who is a Sysadmin?
In a small org, sysadmin can be entire IT staff
– Phone support
– Order and install software and hardware
– Fix anything that breaks from phones to servers
– Develop software
In a large org, sysadmin is part of large IT org
– Specialists instead of “jack of all trades”
– Database admin,
– Network admin,
– Fileserver admin,
– Help desk worker,
– Programmers,
– Logistics

22. 2.4 What does sysadmins do?
1. Add and remove users.
2. Add and remove hardware.
3. Perform backups.
4. Install new software systems.
5. Troubleshooting.
6. System monitoring.
7. Auditing security.
8. Helping users.

23. 2.4.1 User Management
• Creating user accounts
– Consistency requires automation
– Startup (dot) files
• Username and UID namespace management
• Home directory backups and quotas
• Removing user accounts
– Consistency requires automation
– Remove everything, not just homedir and passwd

24. 2.4.2 Hardware Management
• Adding and removing hardware
– Configuration, cabling, etc.
– Device drivers
– Scheduling downtimes and notifying users
• Evaluation and purchase
• Capacity planning
– How many servers?
– How much bandwidth, disk space?
• Data Center management
– Power, racks, environment (cooling, fire alarm)

25. 2.4.3 Backups
• Backup strategy and policies
– Scheduling: when and how often?
– Capacity planning
– Location: On-site vs off-site.
• Installing backup software
• Performing backups and restores
• Monitoring backups
– Checking logs
– Verifying media

26. 2.4.4 Software Installation
• Automated consistent OS installs
• Evaluation of software
• Finding and building open source software
• Purchase of commercial software
• Managing software installations
– Distributing software to multiple hosts
– Package management
– Managing multiple versions of a software pkg
• Patching and updating software
• Scheduling downtimes and notifying users

27. No physical access
– Update process should work without physical access.
Host may not be in known state
– Prior updates may or may not have happened.
– Sysadmins or users may have reconfigured.
Hosts may not be there
– Portable computers may not be on your network when
you’re updating systems.
Host may have live users
– Some updates require no user access or reboots.
 Software Update Difficulties

28.  States of Machines
New
A new machine
Clean
OS installed, but not yet configured for environment.
Configured
Configured correctly for the operating environment.
Unknown
Misconfigured, broken, newly discovered, etc.
Off
Retired/surplussed

29. 2.4.5 Troubleshooting
• Problem identification
– By user notification
– By log files or monitoring programs
• Tracking and visibility
– Ensure users know you’re working on problem
• Finding the root cause of problems
– Provide temporary solution if necessary
– Solve the root problem to permanently eliminate

30. Slide #30
2.4.6 Performance Monitoring
• Automatically monitor systems for
– Problems (disk full, error logs, security)
– Performance (CPU, mem, disk, network)
• Log rotation and backups
• Provides data for capacity planning
– Convince management of need for hardware

31. 2.4.7 Helping Users
• Request tracking system
– Ensures that you don’t forget problems.
– Ensures users know you’re working on their problem;
reduces interruptions, status queries.
– Lets management know what you’ve done.
• User documentation and training
– Acceptable Use Policies
– Document software, hardware (printers), etc.

32. 2.5 Administration Challenges
– Need
● Broad knowledge of hardware and software
● Balancing conflicting requirements
– Short-term vs. long-term needs
– End-user vs. organizational requirements
– Service provider vs. police model
● Working well and efficiently under pressure
● 24x7 availability
● Flexibility, tolerance, and patience
● Good communication skills
• – People think of system admins only when things don't work!

33. Qualities of a Successful System admin
• Customer oriented
– Ability to deal with interrupts, time pressure
– Communication skills
– Service provider, not system police
• Technical knowledge
– Hardware, network, and software knowledge
– Debugging and troubleshooting skills
• Time management
– Automate everything possible.
– Ability to prioritize tasks: urgency and importance.

34. Principles of SA
Simplicity
– Choose the simplest solution that solves the entire problem.
Clarity
– Choose a straightforward solution that’s easy to change,
maintain, debug, and explain to other SAs.
Generality
– Choose reusable solutions and open protocols.
Automation
– Use software to replace human effort.
Communication
– Be sure that you’re solving the right problems and that people
know what you’re doing.
Basics First
– Solve basic infrastructure problems before moving to advanced
ones.

35. Organizations
USENIX: Advanced Computing Systems
Association
LISA: Large Installation System
Administration
SAGE: System Administration Guild

36. SAGE: Goals
1. Advance status of system administration as a
profession.
2. Establish standards of professional excellence
and recognize those who attain them.
3. Develop guidelines for improving the technical
and managerial capabilities of members of the
profession.
4. Promote activities that advance the state of the
art or the community.

37. Conclusion
37
 SA may look after hardware, operating systems, software,
configurations, applications, or security.
 Themes (guideline) which makes up philosophy of system admin
are
 Automate everything
 Document everything
 Communicate as much as possible
 Know your resources, users and business
 Secure organization systems
 Plan ahead and Expect the unexpected

38. Chapter 2 Next class
End of chapter 1
38