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Session2
1. L2B Linux First Course
S ession2
Please visit our Facebook Group
2. L2B First Linux Course
L2B Linux course
Session Outlines:
Linux principles
Bash Basics
Users, Groups and Permissions
Introduction to Bash Scripts
3. L2B First Linux Course
L2B Linux course
Linux Principles
Every thing is a file including hardware
Small, single-purpose programs
Ability to chain programs together to perform
complex tasks
Avoid captive user interfaces
Configuration data stored in text
4. L2B First Linux Course
L2B Linux course
Bash Basics
Shell or bash is an interface between the user
and the kernel
Accepts the commands that a user enters,
interprets these commands, and passes them
to the kernel
5. L2B First Linux Course
L2B Linux course
Bash Basics
Command format:
command [option] [argument]
Option
• Preceded by - if single character
• Preceded by - - if more than one character
Arguments are file names or other data
needed by the command
6. L2B First Linux Course
L2B Linux course
Bash Basics
Full Path
• Begins with a forward slash
• Ends with the file location
Relative path
• Begins with your location
• Ends with the file location
7. L2B First Linux Course
L2B Linux course
Bash Basics
.. refers to the parent directory
. refers to the current directory
Directory names is case sensitive
Names may be up to 255 character
You can use all characters except the
forward-slash
8. L2B First Linux Course
L2B Linux course
Bash Basics
Clear :
• Clear the terminal
Cal
• Display the calendar of current year
cal year
• Display calendar of this year
cal month
• Display calendar of this month
Date
• Display current date
9. L2B First Linux Course
L2B Linux course
Bash Basics
eject cdrom
pwd
cd
• cd ~
• cd path
• cd ..
• cd ../..
• cd .
• cd -
10. L2B First Linux Course
L2B Linux course
Bash Basics
ls
• ls -l
• ls -d
• ls -h
• ls -a
• ls -t
• ls -r
• ls -R
dir
tree not installed by default in Ubuntu
11. L2B First Linux Course
L2B Linux course
Bash Basics
Touch
• If you touched a file which exists you changes it's
modification time
cat & more
nano file_name
12. L2B First Linux Course
L2B Linux course
Bash Basics
mkdir
• mkdir -p
cp
• cp -r
• cp -R
• cp -i
• cp -f
13. L2B First Linux Course
L2B Linux course
Bash Basics
rm
• rm -r
rm -R
rmdir
• rmdir -p
Hint:
• To remove a directory which you exists in, move to
its parent directory or any other directory.
14. L2B First Linux Course
L2B Linux course
Bash Basics
cal
Switching between users
• su
• su -
• sudo
Changing password
• passwd [user_name]
15. L2B First Linux Course
L2B Linux course
Bash Basics
Adding users
• adduser <user_name>
• useradd <user_name>
Removing users
• userdel <user_name>
16. L2B First Linux Course
L2B Linux course
Bash Basics
Getting help
• command --help
• whatis <command>
• man <command>
• info <command>
17. L2B First Linux Course
L2B Linux course
Bash Basics
Getting help
• --help:
– Most commands have the options --help
– It prints a usage statement and list of options and
what they do
– [ any_thing ] >>> It is optional
– ...... >>> It is list of that thing
– < any_thing > >>> It is not optioinal
– { x,y,z } >>> At least one of the these things
– Options separated by | >>> one of them can be
used “or"
18. L2B First Linux Course
L2B Linux course
Bash Basics
Getting help
• whatis
– Short description about the command
– Update it's database daily
» makewhatis as root
19. L2B First Linux Course
L2B Linux course
Bash Basics
Getting help
• man -f
• man -k & apropos
• man -w
• manpath
20. L2B First Linux Course
L2B Linux course
Bash Basics
Getting help
• man page format and how to use it
• man [chapter_number] command
• man sections/chapters
1- user commands
2- system calls / functions provided by the kernel
3- Library calls
4- special files
5- configuration files formats
6- games
7- packages
8- administrative commands
21. L2B First Linux Course
L2B Linux course
Bash Basics
Getting help
• info pages
– More details than man
– Like a web site
– Divided into nodes (*)
– Try >>> (info ls)
22. L2B First Linux Course
L2B Linux course
Bash Basics
Type Tab to complete command lines
Type Tab to command name
For an argument, it will complete a file name
Examples:
• $ xte<Tab>
• $ xterm
• $ ls myf<Tab>
• $ ls myfile.txt
23. L2B First Linux Course
L2B Linux course
Bash Basics
echo command
file command
Virtual consoles
24. L2B First Linux Course
L2B Linux course
Bash Basics Exercise
What man option you will use to search the
description of every manual page for a
keyword.
What man option you will use to search the
entire text (all of the page) of every manual
page.
25. L2B First Linux Course
L2B Linux course
Bash Basics Exercise
What is the option added to “ls” command to
display long list results.
What is the option added to “ls” command to
display long list results with human-readable
descriptions.
26. L2B First Linux Course
L2B Linux course
Bash Basics Exercise
Given the following:
foo -x | -y [-abcde] FILENAME
Which one is right?
• foo -x -y -a file.txt
• foo
• foo -y -abc file1.txt file2.txt
• foo -abc file1.txt file2.txt file3.txt
27. L2B First Linux Course
L2B Linux course
Users, Groups and permissions
Every user is assigned a unique User ID (UID)
UID 0 identifies root
Users' names and UIDs are stored in
/etc/passwd
Users are assigned to groups
Each group is assigned a unique Group ID
(gid)
GIDs are stored in /etc/group
28. L2B First Linux Course
L2B Linux course
Users, Groups and permissions
Every file is owned by a UID and a GID
Permission Types:
•r
•w
•X
To display permissions of a file use
ls -l file
29. L2B First Linux Course
L2B Linux course
Users, Groups and permissions
To change access modes:
chmod [-R] mode file
Where mode is:
u,g or o for user, group and other
+ or - for grant or deny
r, w or x for read, write and execute
Examples:
• ugo+r: Grant read access to all
• o-wx: Deny write and execute to others
30. L2B First Linux Course
L2B Linux course
Users, Groups and permissions
To change access modes:
• chmod [-R] mode file
Where mode is:
• u,g or o for user, group and other
• + or - for grant or deny
• r, w or x for read, write and execute
Examples:
• ugo+r: Grant read access to all
• o-wx: Deny write and execute to others
31. L2B First Linux Course
L2B Linux course
Users, Groups and permissions
Uses a three-digit mode number
first digit specifies owner's permissions
second digit specifies group permissions
third digit represents others' permissions
Permissions are calculated by adding:
• 4 (for read)
• 2 (for write)
• 1 (for execute)
Example:
• chmod 640 myfile
32. L2B First Linux Course
L2B Linux course
Introduction to Bash Scripts
What is a script?
sc extension recommended
Steps to create a script
• Step 1: Use such as vi or nano to create a text file
containing commands:
– #!/bin/bash
– Comments start with a #
– Write your commands.
• Step 2: Make the script executable:
– $ chmod u+x myscript.sh
• Step 3: To execute the new script:
– Use relative path or full path