Mastering the Core Pillars of Linux Administration and Cloud Readiness

1. What is Linux?

Linux is an open-source operating system used in:

• Servers
• Cloud platforms
• DevOps tools (Docker, Kubernetes)
• Supercomputers
• Android phones

Most DevOps and Cloud tools run best on Linux.

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PART 1: Working with the Shell

What is a Shell?

A Shell is a command-line interface where you type commands to interact with Linux.

Example:

$ echo Hello
Hello

Here:

• echo → command
• Hello → argument

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Home Directory

Every user has a home directory.

Symbol:

~

Example:

$ pwd
/home/michael

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Basic Linux Commands (With Examples)

1. pwd – Print Working Directory

Shows where you are:

$ pwd
/home/michael

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2. ls – List Files

$ ls
Asia  Europe  Africa

Useful options:

$ ls -l      # long listing
$ ls -a      # show hidden files
$ ls -lt     # sort by time

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3. mkdir – Create Directory

$ mkdir Asia
$ mkdir Europe Africa America

Create nested directories:

$ mkdir -p Asia/India/Mumbai

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4. cd – Change Directory

$ cd Asia
$ cd ..
$ cd /home/michael

Absolute path:

cd /home/michael/Asia

Relative path:

cd Asia

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5. mv – Move or Rename

Move folder:

$ mv Europe/Morocco Africa/

Rename:

$ mv Munbai Mumbai

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6. cp – Copy Files

$ cp file1.txt file2.txt

Copy directory:

$ cp -r Europe EuropeBackup

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7. rm – Remove Files

$ rm file.txt
$ rm -r foldername

Be careful — no undo.

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8. touch – Create File

$ touch test.txt

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9. cat – View File

$ cat file.txt

Create file using redirect:

$ cat > file.txt
Type content
Ctrl + D

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10. less – View Large Files

$ less largefile.txt

Controls:

• Space → next page
• b → back
• /word → search

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PART 2: Getting Help

1. man

$ man date

2. –help

$ date --help

3. whatis

$ whatis date

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PART 3: Bash Features

1. Command History

$ history

Use ↑ arrow to repeat commands.

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2. Alias

Create shortcut:

$ alias dt=date
$ dt

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3. Environment Variables

Check:

$ echo $PATH
$ echo $SHELL

Create:

$ export OFFICE=caleston

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PART 4: Linux Core Concepts

Kernel vs User Space

• Kernel Space → Core system (CPU, memory, drivers)
• User Space → Applications

System calls connect them.

Example:
When you run:

cat file.txt

It uses system calls like:

• open()
• read()
• close()

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Kernel Version

$ uname -r
4.15.0-72-generic

Breakdown:

• 4 → Kernel version
• 15 → Major version
• 72 → Patch

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PART 5: Working with Hardware

Check CPU

$ lscpu

Check Memory

$ free -m

Check Disk

$ lsblk
$ df -h

Example output:

/dev/sda5  46G  20G  26G  45%  /

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PART 6: Linux Boot Process

Linux boot sequence:

1. BIOS
2. Bootloader (GRUB)
3. Kernel loads
4. systemd starts

Check systemd target:

$ systemctl get-default

Set CLI mode:

$ systemctl set-default multi-user.target

Set GUI mode:

$ systemctl set-default graphical.target

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PART 7: File Types in Linux

Check file type:

$ file test.txt

Types:

Symbol	Type
–	Regular file
d	Directory
l	Link
c	Character device
b	Block device

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PART 8: Package Management

Ubuntu / Debian

Use APT

Install:

$ apt install nginx

Update:

$ apt update
$ apt upgrade

Remove:

$ apt remove nginx

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RHEL / CentOS

Use YUM

Install:

$ yum install httpd

Update:

$ yum update

Remove:

$ yum remove httpd

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PART 9: Searching

find

$ find /home -name file.txt

locate

$ locate file.txt

Update database:

$ updatedb

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PART 10: grep (Search Inside Files)

Search word:

$ grep error file.txt

Ignore case:

$ grep -i error file.txt

Recursive search:

$ grep -r error /var/log

Exclude word:

$ grep -v error file.txt

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PART 11: Redirection

Overwrite:

$ echo Hello > file.txt

Append:

$ echo Hello >> file.txt

Redirect error:

$ command 2> error.txt

Pipe:

$ cat file.txt | grep hello

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PART 12: VI Editor Basics

Open file:

$ vi file.txt

Modes:

1. Command Mode
2. Insert Mode
3. Last Line Mode

Insert:

• Press i

Save:

:w

Quit:

:q

Save and Quit:

:wq

Force Quit:

:q!

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PART 13: Users and Groups

View users:

$ cat /etc/passwd

Check user ID:

$ id michael

Switch user:

$ su -

Use sudo:

$ sudo apt install nginx

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PART 14: Disk Usage

Check disk usage:

$ df -h

Check folder size:

$ du -sh foldername

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PART 15: Compression

gzip:

$ gzip file.txt
$ gunzip file.txt.gz

bzip2:

$ bzip2 file.txt

tar:

Create archive:

$ tar -cf backup.tar folder

Extract:

$ tar -xf backup.tar

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Final Summary

Linux Basics includes:

• Shell commands
• File management
• Users and permissions
• Package management
• Boot process
• Kernel basics
• Hardware monitoring
• Text editing
• Searching and redirection