1. Introduction to UNIX

2. *nix Linux, Solaris, BSD, macOS…
We will be using Ubuntu and centOS primarily

3. UNIX OS
3 parts:
Kernel
Shell
Programs

4. Kernel Interacts with hardware directly Manages memory
Handles filestore and communications

5. The Shell Interface between user and kernel Command line interpreter
Commands are programs
The Shell is also a program

6. Programs Everything is a process or a file Process – executing program
Each process has a unique process identifier (PID)
File – collection of data created by users

7. Filesystem

8. Basic Commands - Syntax
Example: ls -a /home
The Shell expects tokens to be separated by spaces
Typically first token is your command
Subsequent tokens are arguments
Arguments that start with - or -- are options
Non-option arguments passed to command

9. Basic Commands ls (list) touch myfile.txt Options: -a, -l, -h…
Argument: /home/username/
touch myfile.txt
Creates a blank file named myfile.txt

10. Basic Commands cd (change directory) pwd
If no destination is provided it defaults to home directory
. is your current directory
.. will take you to the parent directory
pwd
Print working directory (where you are in the filesystem)

11. Basic Commands mkdir (make directory) rmdir (remove directory)
Must provide new directory name
rmdir (remove directory)
rm (remove)
Delete a file
Common to see rm –rf /path/to/file
Be careful, -r is recursive and -f is force

12. Basic Commands cp (copy) mv (move) cp source destination
ex: cp myFile /home/anotheruser/
mv (move)
mv source destination
Use this to rename files

13. Basic Commands cat vim (or emacs) View contents of file Edit file
There are built in tutorials for both of these
vimtutor
Start emacs, type “Ctrl –h” followed by “t”

14. Basic Commands
For more information on any command type “man <command>”
Shows command usage
Shows all options with explanations

15. Basic Commands Ctrl C – kill process Ctrl D – end of file
Ctrl Z – suspend process
Enter “bg” to resume process in background
Enter “fg” to bring it to foreground again

16. Other Useful Commands find /home -name <filename> df -h
Find a file in your home directory by name
df -h
Display how much disk space has been used

17. Filters head tail grep Show first n lines (10 by default)
Show last n lines (10 by default)
grep
Search for a given pattern

18. Wildcards * ? [ ] Zero or more characters
ls *.png (list all pngs in current directory) ?
Single character
ls ?a* (list all files whose 2nd letter is “a”)
[ ]
Range of characters
ls [a-dj]*.png (list all pngs that start with a,b,c,d, or j)

19. Redirecting Output cat list1.txt list2.txt > bothLists.txt
redirects output of cat to a text file called bothLists.txt
cat list1.txt list2.txt >> bothLists.txt
appends output of cat to bothLists.txt
command1 | command2
called a pipe
redirects output of command1 to input of command2
sort < names.txt
redirects input to come from file
sorts content of names.txt

20. Combining Commands cal 2017 ; ls -a
runs two commands in sequence
sudo apt-get update && sudo apt-get upgrade
downloads the list of available updates
installs them if the previous command was successful
./myscript || echo “Script Failed!”
runs myscript
prints “Script Failed!” if script failed
Added combination of commands on one line, since it was in Welcome Week exercises. Feel free to skip if nesessary.
Max

21. SSH Secure Socket Shell ssh username@ip Remote access
Login to another box on your network

22. Path Path – location of file/directory
Absolute path – location of file/directory from root directory
/usr/local/bin
~/Desktop (~ will refer to your home directory)
Relative path – location of file/directory relative to another directory
../home/anotheruser

23. Path cont. $PATH /usr/bin/python (invoke python interpreter)
Shell will search for a disk utility, if command is not built-in
/usr/bin/python (invoke python interpreter)
./a.out (run program compiled in current directory)

24. Access Control Every file is owned by a user and a group
Permissions allow users/groups to read/write/execute files
Root can read/write/execute anything
Other users can get root privileges with “sudo”
“su” allows a user to change the login session owner

25. User Info - /etc/passwd
Each line contains login info for a single user
Format:
Username
Password Placeholder
User ID
Group ID
Comment field
Home directory
User shell

26. User Info - /etc/shadow
Each line contains hashed password for single user
Format:
Username
Salt and hashed password
Last password change
Days of warning prior to password expiration
Last 3 fields denote days before account is made inactive

27. Permissions File type, mod bits Number of hard links Owner Group Size
Modification time
filename

28. Permissions r – read (4) w – write (2) x – execute (1)
To change: chmod <modes> <files>
chmod 754 myScript.sh
7 – rwx for user (file’s owner)
5 – rx for group (member’s of file’s group)
4 - r for other (everyone else)

29. Bash Extension of Bourne Shell When the Shell gets a command it
There are others, like Korn Shell
When the Shell gets a command it
Expands aliases
Checks if command is a shell built in
If not, assumes command is a program

30. Bash Scripting – Hello World

31. Bash Scripting #!/bin/bash Need to “chmod 755 hello.sh”
Invoke appropriate interpreter
Need to “chmod 755 hello.sh”
Executable for user, group and other can read/write
To run “./hello.sh”

32. References
OneNote