CNS 6123: Advanced Networking and
System Administration
For MSc in Computer Networking and Security (CNS) Students
1. Introduction to Systems Administration
By Dr. Samuel Asferaw
2017/2018
Contents:
• Introduction
• General Introduction
• Over View of Network Operating Systems (NOSs)
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CNS 6123: Advanced Networking and
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General Introduction
Contents:
1.
2.
3.
4.
5.
6.
7.
8.
What is system administration?
What do sysadmins do?
Administration Challenges
Principles and First Steps
Organizations and Certifications
Maturity and Complexity
SAGE Code of Ethics
X-Windows Operating Systems
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What is a system?
System: An organized collection of computers
interacting with a group of users looking for services to
accomplish work.
PCs
Network
Services
Use
run on
Servers
Users
help to accomplish work
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System State
System policy: specification of a system’s configuration
and its acceptable usage.
System state S(t): the current configuration (files,
kernel, memory or CPU usage) of a system.
Ideal states S*(t): states of the system that match the
system policy. Over time, the system state shifts
away from the ideal state.
System administration: modifying the system to bring
it closer to S*(t).
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What do sysadmins do?
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
Large org: sysadmin is one of many IT staff
– Specialists instead of “jack of all trades”
– Database admin, Network admin, Fileserver
admin, Help desk worker, Programmers, Logistics
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What do 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. Help users
9. Communicate
All are common activities for sysadmin.
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User Account Management
Creating user accounts
– Consistency requires automation
– Startup (dot) files
Removing user accounts
– Consistency requires automation
– Many accounts across different systems
Namespace management
– Usernames and UIDs
– Multiple namespaces or SSI?
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Hardware Management
Adding and removing hardware
– Configuration, cabling, etc.
Purchase
– Evaluate and purchase servers + other hardware
Capacity planning
– How many servers? How much bandwidth, storage?
Data Center management
– Power, environment (cooling, fire alarm)
Virtualization
– When can virtual servers be used vs. physical?
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Data Backups
Backup strategy and policies
– Scheduling: when and how often?
– Capacity planning
– Location: on-site vs. off-site.
Monitoring backups
– Checking logs
– Verifying media
Performing restores when requested
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Software Installation
Evaluation of software
Automated consistent OS installs
– Desktop vs. server OS image needs.
Installation of software
– Purchase, find, or
build custom software.
Managing software installations
– Distributing software to multiple hosts.
– Managing multiple versions of a software pkg.
Patching and updating software
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System Monitoring
Automatically monitor systems for
– Problems (disk full, error logs, security)
– Performance (CPU, mem, disk, network)
Security
– Passwords
– Break-ins
Capacity
– Disk, RAM, CPU, network
System logs
– Examination
– Periodic rotation and truncation
– Archival storage (at least
summaries)
Provides data for capacity planning
– Determine need for resources
– Establish case to bring to management
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Troubleshooting
Problem identification, diagnosis, and resolution
– By user notification
– By log files or monitoring programs
Finding the root cause of problems
– Provide temporary solution if necessary
– Solve the root problem to permanently eliminate
• Often quite difficult!
Often requires
– Broad and thorough
system knowledge
– Outside experts
– Luck
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User Assistance
• Time intensive!
• Techniques
– Help desks
– Trouble-ticket systems
•
•
•
•
Software availability and usage
Software configuration settings
Hardware usage, maintenance, and troubleshooting
User documentation and training
– Policies and procedures
• Schedule and communicate downtimes
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Security Concerns
• System logging and audit facilities
– Evaluation and implementation
– Monitoring and analysis
– Traps, auditing and monitoring programs
• Unexpected or unauthorized user detection
• Monitoring of security advisories
– Security holes and weaknesses
– Live exploits
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Communicate
Customers
– Keep customer appraised of process
• When you’ve started working on a request
• When you make progress, need feedback
• When you’ve finished
– Communicate system status
• Uptime, scheduled downtimes, failures
– Meet regularly with customer managers
Managers
– Meet regularly with your manager
– Write weekly status reports
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Specialized Skills
Heterogeneous Environments
Integrating multiple-OSes, hardware types, or network
protocols, distributed sites.
Databases
SQL RDMS
Networking
Complex routing, high speed networks, voice.
Security
Firewalls, authentication, biometrics, cryptography.
Storage
Network Attached Storage (NAS), Storage Area Networks
(SANs), cloud storage.
Virtualization and Cloud Computing
VMware, cloud architectures.
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Practice of sysadmin
• Common practice may not be good practice
– There are three reasons for common practice:
• Someone did it and others followed blindly;
• Believe it is good after careful thought;
• An arbitrary choice had to be made;
– Think for yourself
– Pay attention to experts but don’t automatically
believe anyone
– Every choice needs a reason
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Practice of sysadmin ...
• Good practices
– Look for answers in manuals, newsgroups, and archive of
mailing lists
• Usually “google” helps for most common problems
– Use controlled trial and error for diagnosis
– Listen to people who tell us there is a problem. It might be
true
– Write down problems and solutions in a log book, and
write down experiences
– Take responsibilities for our actions
– Remember to tidy things up regularly
– After learning something new, ask yourself “How does
this apply to my work?”
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System administrator (sysadmin)
• Successful System Administrators
– No stereotypes, “White/black Cats Theory”
– Normally if one can keep the users happy she is successful
(which is very difficult)
– Life-long learning skills. One’s proud knowledge and
expertise today may be obsolete tomorrow (Be prepared
to be jobless if you do not keep learning)
• Some myths for new sysadmin
– There exists a right answer for every problem
– Things should always work in the way we expect
– Every problem should have a happy end
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Challenges of System Administration
• Not only just installing system/software, also
about planning and designing an efficient
community of computers
• Design a logical and efficient network
• Easy upgrade for a large number of computers
• Decide what and where services are installed
• Plan and implement security
• Provide a comfortable environment for users
• Develop ways of fixing problems and errors
• Keep track of new technology and software
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Challenges of System Administration ...
• Need
– Broad knowledge of hardware and software
– To balance conflicting requirements
• Short-term vs. long-term needs
• End-user vs. organizational requirements
• Service provider vs. police model
–
–
–
–
To work well and efficiently under pressure
24x7 availability
Flexibility, tolerance, and patience
Good communication skills
• People think of sysadmins only when things don't
work!
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Principles of SA
Simplicity
– Choose the simplest solution that solves the entire problem
– Work towards a predictable system
Clarity
– Choose a straightforward solution that’s easy to change, maintain,
debug, and explain to other SAs
Generality
– Choose reusable solutions that scale up; use 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 advanced ones
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Qualities of a Successful Sysadmin
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
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First Steps to Better SA
Use a request system
– Customers know what you’re doing
– You know what you’re doing
Manage quick requests right
– Handle emergencies quickly
– Use request system to avoid interruptions
Policies
– How do people get help?
– What is the scope of responsibility for SA team?
– What is our definition of emergency?
Start every host in a known state.
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Types of Sites
Small
2-10 computers, 1 OS, 2-20 users.
Small staff size requires outsourcing to obtain most
specialized skills.
Midsized
11-100 computers, 1-3 OSes, 21-100 users.
Large
100+ computers, multiples OSes, 100+ users
Outsources to reduce costs, some specializations.
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Organizations
USENIX: Advanced Computing Systems
Association
LISA: Large Installation System Administration
SAGE: System Administration Guild
LOPSA: League of Professional System
Administrators
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Certifications
•
•
•
•
•
•
CCNA, CCNP, CCIE (Cisco)
cSAGE (SAGE)
MCSA (Microsoft)
RHCE (Red Hat)
SCSA (Sun)
VCP (VMware)
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SAGE Job Descriptions
Novice
OS familiarity, help desk skills
Junior
Can use OS system administration tools
Intermediate
Understanding of distributed computing, common servers,
automate small tasks, independent action
Senior
Understanding of scaling issues, including capacity planning,
solve problems by addressing root cause, higher level
programming abilities, write proposals for purchasing, data
center planning, etc.
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SA Maturity Model (SAMM)
1. Ad Hoc
Ad-hoc non-repeatable solutions, firefighting.
2. Repeatable
Some repeatable processes.
3. Defined
Documented standard processes
4. Managed
Process effectiveness measured, adapted.
5. Optimized
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Maturity and Complexity
Low downtime, high
efficiency
Maturity
Scalable but time
lost in process
Constant firefighting,
high downtime
Works, but hard
to scale up
Complexity: increasing numbers of systems and/or services
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Tool Maturity Levels
1. Ad Hoc
OS GUI, CLI, or web administration interfaces.
2. Repeatable
Version control (RCS, SVN, GIT), request tracker
3. Defined
Automatic monitoring (Nagios, monit, god)
4. Managed
Configuration management (AutomateIt, cfengine)
5. Optimized
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SAGE Code of Ethics
•
•
•
•
•
•
•
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Professionalism
Personal Integrity
Privacy
Laws and Policies
Communication
System Integrity
Education
Social Responsibility
http://www.sage.org/ethics/
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X-Windows
•
•
•
•
Mac Operating System
Unix Operating System
Linux Operating System
etc
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Which OS to learn to admin?
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Brief History of UNIX
• Originated as a research project in 1969 at AT&T Bell Labs
– Made available to universities (free) in 1976
• Berkeley UNIX started in 1977 when UCB licensed code
from AT&T.
– Berkeley Software Distribution started in 1977 with 1BSD, and
ended in 1993 with 4.4BSD
– Licensing costs from AT&T increased, so Berkeley attempted to
remove AT&T code, but ran out of funds before completion.
– Final release of AT&T-free code called 4.4BSD-Lite.
• Most current BSD distributions (FreeBSD, NetBSD, OpenBSD) are
derived from 4.4BSD-Lite.
• Most commercial versions of UNIX (Solaris, HP-UX) are
derived from the AT&T code
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What is Linux?
much is courtesy of www.kernel.org
• Linux is a clone of the operating system Unix, written by a looselyknit team of hackers across the Net.
• Like any modern full-fledged Unix, Linux includes:
–
–
–
–
true multitasking
proper memory management and virtual memory
shared libraries and shared copy-on-write executables
TCP/IP networking
• Linux really refers to the kernel
– Most commands and apps are really separate programs, not specific to
Linux, and often are part of the Free Software Foundation's GNU
project.
• Linux was first developed for 32-bit x86-based PCs (386 or higher).
These days it also runs on dozens of other processors.
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Brief History of Linux
• Created as a personal project (and still
controlled) by Linus Torvalds, a Finnish
graduate student, in 1991
• Conceived as an offshoot of Minix (a model OS)
– Not derived from AT&T or BSD UNIX code
• Red Hat (one of many Linux vendors) founded
in 1993
• Kernel v1.0 released 1994
• Most recent (Jan 2016) kernel release is 4.4?
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Where to get answers?
• Linux/UNIX documentation can be found in
many places
– Manual pages (man pages, using man command)
– Texinfo documents (read with info command)
– HOWTOs – focused descriptions of a topic
– Distribution-specific documentation
– Your favorite Web search engine
• Will typically find online versions of the above
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Where to get answers?
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Contents:
• Introduction
• General Introduction
• Over View of Network Operating Systems (NOSs)
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Overview of Network Operating
Systems (NOSs)
Distributed Data
Processing
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Overview of Network Operating
Systems (NOSs)
Contents:
•
•
•
•
•
•
System
Network
Operating System
Network Operating System
Features
Remote Login with an
example
• Remote file transfer
(Example)
• Anonymous FTP method
2017/2018
• Network and Operating
System Security
• Novell NetWare and
protocols
• Difference between OS and
NOS
• Summary
• Sources
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What is a system?
• set of interacting or interdependent entities
Multiple meaning:
• collection of organized things
• way of organizing or planning
• whole composed relationship among the members
Characteristics:
• have a structure that is defined by its parts and
processes
• tend to function in the same way
(involves inputs and outputs of material)
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What is a Network?
• is a communication path between two or more systems
• vary by the protocols used, the distances between nodes,
and the transport media
• TCP/IP is the most common
network protocol
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Operating System
• Program that manages the computer hardware
• Provides a basis for application programs and acts as an
intermediary between the user and the hardware
• Offers a reasonable way to solve the problem of creating a
usable computing system
Example Types of Operating Systems: Linux and Unix
Microsoft Windows
Mac OS X
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User 1
Compiler
User 2
Assembler
User 3
........
Text editor
User n
Databases
System
System and Application Programs
Operating System
Computer Hardware
Figure: Abstract view of the components of a computer system
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Network Operating System
• provides an environment in which users, who are aware of
multiplicity of machines, can access remote resources either:
-> logging in to the remote machine* or
-> transferring data from the remote
machine to their own machines
• mostly used with local area networks and widearea networks
*Remote machine: refers to a computer connected to the network
which a user is using
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Network Operating System Features
• Provides basic operating system features; support for
processors, protocols, automatic hardware detection,
support multi-processing of applications
• Security features; authentication, authorization,
access control
• Provides names and directory services
• Provides files, print, web services, back-up and
replication services
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Network Operating System Features ...
• Supports Internetworking such as routing and WAN
ports
• User management and support for login and logoff,
remote access, system management
• Clustering capabilities, fault tolerant and high
availability systems
Cluster: = group of linked computers working together
closely, connected to LAN
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Remote Login with an Example
• important function of a NOS is to allow users to log in remotely
• internet provides the telnet facility for this purpose
• Example: a user at AAU wishes to compute
on “cs.DBU.edu,“ a computer that is located at DBU
University
-> user must have a valid account on that machine
to log in remotely the user issues the command:
telnet cs.DBU.edu
Command results in the formation of a socket connection between
the local machine at AAU and the “cs.DBU.edu“ computer
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Remote Login with an Example...
• connection has been established
• transparent, bidirectional link that all characters
entered by the user are sent to a process “cs.DBU.edu“
• all the output from that process is sent back to the
user
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Remote File Transfer
• Provide a mechanism for remote file transfer from
one machine to another
• Each computer maintains its own local file system
• User: “cs.AAU.edu“ wants to access a file located on
another computer “cs.DBU.edu“ file must be copied
from the computer at DBU to the PC at AAU
• Internet provides the transfer with file transfer
protocol (FTP) program
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Remote File Transfer Example
• User on “cs.AAU.edu“ -> copy Java program
Server.java that resides on “cs.DBU.edu“
• Invoke FTP program ftp cs.DBU.edu
• Login name and password
• Correct information has been received, user must
connect to the file Server.java and after copy the file
by executing get Server.java
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Remote File Transfer Example...
• File location is not transparent to the user
• No real file sharing
• Remember: User at the AAU must have login
permission on “cs.DBU.edu“
• FTP provides a way to allow a user to copy files
remotely
• Remote copying is accomplished through “anonymous
FTP‘‘ method
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Anonymous FTP Method
• File to be copied (Server.java) must be placed in a
subdirectory (ftp) with the protection set to allow the
public to read the file
• User uses ftp command
• Login name: “anonymous“ and password
• Anonymous login is accomplished
• User is allowed to access only those files that are in the
directory tree of user “anonymous“
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Anonymous FTP Method ...
www.trainsignaltraining.com/.../ftp_iis7_10.png
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Anonymous FTP Method ...
• FTP mechanism is implemented (similar to telnet
implementation)
• Daemon on remote site -> watches for connection
requests to system‘s FTP port
• Login authentication is accomplished ->user can
execute commands remotely
• telnet daemon executes any command for user
• FTP daemon responds to a predefined set of filerelated commands:
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Anonymous FTP Method ...
• Get: transfer a file from the remote machine to the
local machine
• Put: transfer from the local machine to the remote
machine
• Ls or dir: list files in the current directory on the remote
machine
• Cd: change the current directory on the remote
machine
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Network and Operating System Security
• OS: system must protect itself
• Runway process could constitute an accidental denialof-service attack
• Query to service could reveal passwords
• Stack overflow could allow the launching of an
unauthorized process
• List of possible breaches is almost endless
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Network and Operating System Security...
• Travels over private leased lines, shared lines like the
internet, wireless connections, or dial-up lines
• Intercepting these data could be harmful as breaking
into a computer
• Interruption of communications could constitute a
remote denial-of-service attack, diminishing user‘s use
of and trust in the system
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Novell NetWare
• Is a NOS
• Used cooperative multitasking to run several services
on a PC
• File sharing instead of disk sharing
• NDS (Novell Directory Services)
• Server administration
• Desktop Management
• Software distribution
• Integrated cache
• Enhanced security CNS 6123: Advanced Networking and
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Novell NetWare Protocols
• Are widely used for PC LANs
• Windows XP Nwlink protocol connects the NetBIOs to
NetWare networks
• In combination with a redirector this protocol enables
a Windows XP client to connect to a NetWare server
• Some NOSs for DOS and Windows system include
Novell NetWare: Windows NT and 2000 OS/2 etc.
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Novell NetWare Protocols...
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Difference between Operating System and
Network Operating System
• OS runs on the
computer itself
Example: Windows
• Network OS run on a server
and can be accessed
through client machines
connected on the network
Example: Novell Netware and
Linux run on a server can be
used as NOS
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Summary
• NOS provides features such as file sharing across the network
• Includes communication scheme
• Allows different processes on different computers to exchange
messages
• Computer running a NOS acts autonomously to all other
computers on the network
• It is aware of the network – able to communicate with other
networked computers
• Network operating systems can be embedded in
a router or hardware firewall that operates the functions in
the network layer (layer 3)
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Summary...
• The term network operating system is used to refer
to two rather different concepts:
• A specialized operating system for a network device such
as a router, switch or firewall.
• An operating system oriented to computer networking, to
allow shared file and printer access among multiple
computers in a network, to enable the sharing of data,
users, groups, security, applications, and other
networking functions, typically over a local area
network (LAN), or private network.
• However, this sense is now largely historical, as
common operating systems generally now have such
features included.
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Thank you for attention!! !
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