This document provides an overview and outline of Session 2 for the L2B Linux First Course. It covers Linux principles including the concept that everything is a file, Bash basics such as command syntax and navigation, and users/groups/permissions including file ownership and permissions. It also briefly introduces Bash scripts, describing them as files containing commands and the process to create and execute a script.

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

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