Review for Exam
III
Chapter 20 Electronic Mail
User agent (MUA) - allows users to read and compose mail
Transfer agent (MTA) - forwards messages among machines
Delivery agent (DA) - places messages in the receiving users
mailboxes
Designate a master mail machine and a mail home for each user
Mail aliases /etc/aliases allow mail to be redirected on a
system wide basis
Special mail aliases:
File
containing a list of addresses
File to
which messages are to be appended
Messages
piped to a command
.forward allows users to reroute their own mail
Sendmail/Postfix/Exim is a transport agent for UNIX systems
Run a version of Sendmail/Postfix/Exim with the latest
security fixes
SMTP: protocol used to transfer mail between machines
Chapter 21 Network Management and Debugging
ping can be used to check for network faults
traceroute can be used to find the route a packet takes on the network
Send multiple ping packets to check for unreliable links
Use netstat to find networks with
too many collisions
SNMP: device management protocol
MIBs (Management Information Bases) define what information
is available for a device
Devices can be manipulated if they are part of the same
community
A device sends a SNMP trap when a problem is detected
Network management workstations can visually display the
status of a network
These are expensive, but invaluable when managing large
networks
Know the difference between SNMP and SMTP
Chapter 22 Security
Security is the inverse of convenience
UNIX is not a secure operating system, but it can be made
more secure.
UNIX does not have levels of security, security is binary.
Measures to help improve security:
Shadow
passwords - Hard to break passwords
Prohibit
group logins
Use ssh in
place of telnet and rsh
Use security
tools: Nmap, Nessus, John,
Bro, Snort, OSSEC, TCP wrappers
Setuid programs need to be checked for security holes
VPN: Makes a remote network appear as if its directly
connected
Chapter 23 Web Hosting
The web server runs at TCP port 80, SSL uses pot 443
Internet service providers (ISPs) provide direct connections
to the internet
LAMP stack: Linux, Apache, MySQL, Perl/PHP/Python
CGI: allows documents to be created on-the-fly dynamically
Virtual hosts allow multiple websites to run on one computer
Chapter 24 Virtualization
Allows us to combine underutilized servers
High availability live migration
Live migration: Migrate virtual
machines between machines
VMware is the biggest player in the
virtualization market
Cloud Computing - Alternative to
locally run server farms
Amazon Web Services AWS
SAAS: software as a service
virtualized applications
Chapter 25 The X Windows System
Client/Server model
Server runs on the system with the display
Clients can run anywhere
Remote connections should be tunneled though ssh
Chapter 26 Printing
CUPS is the Linux printing system
CUPS has replaced BSD and System V printing
BSD: lpc, lpr,
printcap
SystemV: lpadmin, lp,
cancel
Print filters convert your document to a form that can be
printed by the printer
Inkjet printers are much more expensive to operate than laser
printers
Chapter 27 Data Center Basics
Data centers need: secure space, racks to hold equipment,
clean power, cooling and network connectivity
Use hot and cold aisles for more efficient cooling
Be careful of static electricity when handling boards and
memory, need to be properly grounded
Sometimes reseating boards can fix problems
Preventative maintenance is needed for mechanical devices:
printers, tape drives, fans
Types of maintenance contracts: on-site, board swap
Maximize your warranties when possible: disks: 5 year,
memory: lifetime
Evaluate systems based on life-cycle cost
$10K system
$1000 h/w maintenance $800 s/w maintenance
3 year-life
cycle cost is:
Chapter 28 Green IT
Minimize the equipment you buy
Minimize power consumption
Minimize size of data center
Minimize consumables
Minimize (recycle) outputs
Maximize utilization of your equipment
Chapter
29 Performance Analysis
Usually there is no magic fix for performance problems
Be careful your tuning does not create problems in another
part of the system
Things that can be done to improve performance:
Schedule
resource hogs to run during off-hours
Add memory
Split the
load across multiple systems
Resources that can be tuned: CPU, memory, disk, network
Add more of the resource that is the bottleneck or reduce the
demand
Adding extra resources will only improve performance if that
resource is maxed out
(a faster
CPU does not make a disk-bound process any faster)
Use vmstat to analyze memory and
paging
Use iostat to analyze disk usage
Disks max out at between 100-300 seeks per second
Spread swap space across multiple drives (spindles)
What to check for when the system gets real slow:
Use top to
look for jobs that are hogging the CPU
Run vmstat to see how much paging is occurring
Check for a
NFS or DNS server on the network that is hung
Chapter 30 Cooperating with Windows
File and printer sharing
CIFS is better than NFS
Samba CIFS for UNIX
VNC and RDP to share remote desktops
SSH secure connection
Cygwin: Unix commands on Windows
Linux clients
can use Windows Active Directory for authentication
Things you can
do for professional development and life-long learning:
Join
Professional Organizations: ACM, SAGE
Attend Conferences: LISA, Linux, Unix
Linux Certification
Understanding
of professional, ethical, legal, security and social issues and
responsibilities:
What
are ethical and legal problems if your company uses more copies of a software
package than they have purchased?
Ethical: Its wrong violation of the
license agreement
Legal: Your company could be subject to large fines if reported or audited
Ability to
communicate effectively with a range of audiences:
How
does the systems administrator communicate effectively with technical and
non-technical users?
Technical:
Can use technical language and terms with
technical users
Higher expectation of technical proficiency
Non-Technical:
Low expectations of technical proficiency
Refrain from using technical language and
terms with non-technical user
Refrain from making fun of non-technical
users
Avoid sysadmin
syndrome be willing to help
Perl
Write a script to find blank passwords in /etc/passwd:
($user,$passwd,$uid,$gid,$gcos) = split(/:/);