1. CS3695/M6-109 – Network Vulnerability Assessment & Risk Mitigation –
Introduction to Unix & Linux

2. Objectives
Know basic Linux commands, such as: ls, cd,|, more, mkdir, rmdir, touch, rm, cp, su, vi, chmod, w, who, finger
Know commands are case sensitive
Know the difference between ssh and telnet
Introduce vi as an editor
Know how permissions work

3. Linux/Unix What you should know
Linux/Unix commands are arcane and cryptic and often silly looking
Linux command are case sensitive!
Some commands have flags for additional optional control like this:
…ls -al or rm -r
You can put multiple commands on the same line:
…ls ; pwd
You can auto-complete commands with the tab key
You can correct a bad command with ^^

4. Linux Distributions

5. Linux Live CD-ROMs EC-Council
A LiveCD is an operating system (usually containing other software as well) stored on a bootable CD-ROM that can be executed from it, without installation on a hard drive
Knoppix Live CDs are widely used in the Linux community
It is completely customizable
EC-Council
Source:
Copyright © by EC-Council

6. Connecting to Linux
You can telnet or ssh if you want

7. You can get help with the man
man <command> for manual pages
Windows equivalent:
cmd /?
cmd –help

8. Working with Man man [command] Within man: spacebar/f = forward
b = back
q = quit
/ = search forward
? = search backward
n = repeat search

9. Reading Files
Windows equivalent:
type filename

10. Linux ls
You can list directories with ls
Windows equivalent:
dir

11. More on ls Time or year of last Mod Permissions Ownership And group
First Bit
- = file
l = link
d = directory
b = block device (disk drive)
c = character device (serial port or terminal)
Permissions
Ownership
And group
membership
Size
Date of last Mod
Time or year of last Mod
Filename
Text
# of Links

12. Ownership and Permissions
Three levels of ownership and permissions
User
Group
Everyone
Within these groups you can specify permissions:
• Read
• Write
• execute
File access levels
Permissions

13. Who owns what?

14. Change the group association of files and directories
chgrp <group> <filename>
chgrp –R <group> <directory>
To change the group association of a directory and all of its contents us the –R switch

15. You can change ownership!
chown <userid> <filename>
chown –R <userid> <directory>
The –R switch again

16. Change permissions

17. Or Use chmod Or use the chmod command to set the individual levels:
--- 7=rwx, 3=-wx, 1=--x

18. Windows CLI Permissions
On windows chmod is not available.
Windows command line utility called CACLS.
You can use it as follows:
CACLS files /e /p {USERNAME}:{PERMISSION}
/p : Set new permission
/e : edit ACL instead of replacing it.
{USERNAME} : Name of user
{PERMISSION} : Permission can be:
R - Read
W - Write
C - Change (write)
F - Full control

19. CACLS (Continued)
For example grant Rocky Full (F) control with following command (type at Windows command prompt):
C:> CACLS files /e /p rocky:f
Read complete help by typing following command:
C:> cacls /?
Ref:

20. Change directories with cd and find yourself with pwd
You can change directories and find yourself…
cd to change directory, pwd to display your current directory

21. You can Pipe I/O | and more = one screen at a time Windows equivalent:
Same

22. The redirect > It doesn’t have to go to the screen.
Windows equivalent:
Same

23. You can make a directory with mkdir
mkdir creates directory
Windows equivalent:
Same

24. You can “touch” Make a file with touch Windows equivalent:
No real equivalent…

25. You can copy
cp is used to copy a file
Windows equivalent:
copy

26. You can move files and directories
mv is used to move (or rename) a file
Windows equivalent:
move

27. You can remove files and directories
Windows equivalent:
del
rm and rmdir
You must remove everything from the directory to use rmdir

28. ps ps stands for Process Status Shows currently running processes
Windows equivalent:
tasklist
If looking for a specific process combine with findstr
tasklist | findstr StringValue
ps stands for Process Status
Shows currently running processes
Depending on disto may require a –A to see all processes.

29. kill kill is used to terminate a running process
Can be used with the optional signal-number for special cases
Some of the more commonly used signals:
HUP (hang up)
INT (interrupt)
QUIT (quit)
ABRT (abort)
KILL (non-catchable, non-ignorable kill)
ALRM (alarm clock)
TERM (software termination signal)
Windows equivalent:
taskkill
taskkill /PID # /F

30. awk
awk scans each input file for lines that match any of a set of patterns specified
The –F option defines the input field separator
An input line is normally made up of fields separated by white space denoted $1, $2, etc
awk -F":" '{ print "User: " $1 “ hash” $2 }' /etc/shadow
Gives us user: Student hash: $6jlkfawdp8o7532oiuq5qlijfds
Instead of Student:$6jlkfawdp8o7532oiuq5qlijfds:16081:0:::
Windows equivalent:
No simple equivalent

31. What about that shell? Common Unix shells
Sh: This shell, the original, often called the Bourne shell, not too flexible, great for scripting
Csh and tcsh: The family of shells adds great interactive uses but discards the popular scripting support that sh offers. It favors C “programming” like type syntax
Ksh, bash, zsh: These provide a good mix of scripting and interactive capabilities, bash is very similar to sh and is often referred to as “Bourne again shell”…hence bash
Windows equivalent:
Command or CMD

32. What is my shell?
Echo $shell

33. I think you should change your identity
su: substitute user
When: to log in as a different user or to start a new login shell
To login as a different user
su asr
To start a new login shell
su – rharkins {the hyphen will force a new login shell}
To return to the previous shell
exit
Use su without anything else to get to root (you will be prompted for the root password) su
To perform a single task as root use sudo
sudo tcpdump
Windows equivalent:
For a command shell:
runas /profile cmd

34. What editor should I use
VI: Powerful but very cranky editor. It is universally available, and therefore a good reason to learn it at some time. Literally no help while in the editor so you just have to know it.
Two modes…input and command…get used to it.
You could …”man vi”…to read help
Windows equivalent: edit and notepad
NOTE: Both edit and notepad have problems across a network from a command shell

35. VI
Notice all the nice help you get in this editor!

36. Some VI Help One command to help with vi
As soon as you open vi, use the command
:set showmode
This displays which mode you are in…

37. USE THE vi Cheat Sheet!

38. Other Editors
PICO: One of the newer UNIX/LINUX editors. Popular because it is easy to use.
Usually ships with the pine program…so if you have pine you should have PICO.

39. PICO
Much better huh?

40. System info
Windows equivalent:
systeminfo
The uname command

41. To snoop with who, w, finger
Windows equivalent:
net session
Requires admin priv
Who is logged on to system

42. grep is Your Friend
grep searches the named input FILEs for lines containing a match to the given PATTERN. By default, grep prints the matching lines
grep <pattern> <file>
grep host zone.txt
Windows equivalent:
find

43. AWK awk - pattern-directed scanning and processing language
scans each input file for lines that match any of a set of patterns specified
each pattern there can be an associated action
Mostly used for pulling out information like grep but allows for more options
awk -F":" '{ print "User: " $1 “ hash” $2 }' /etc/shadow