Linux Server Administration – Complete Notes (CIITM Dhanbad)

Source: Dev.to

UNIT – I : Linux Introduction, File System & Basic Commands

1. Introduction to Linux

• Linux is a free, open-source, secure and stable operating system.
• Based on UNIX, widely used in:
  • Servers
  • Cloud systems
  • Networking
  • Cybersecurity
  • Development
• Known for:
  • High security
  • Fast performance
  • Virus resistance
  • Multi‑user environment

2. Basic Features of Linux

• Multiuser & multitasking
• Portable & open‑source
• Strong networking support
• Highly customizable
• Powerful shell & scripting

3. Flavors (Distributions) of Linux

Common Linux distros:

• Ubuntu
• Debian
• RedHat (RHEL)
• Fedora
• CentOS
• Kali Linux
• Linux Mint

4. Advantages of Linux

• Free & open source
• Highly stable
• Virus free
• Powerful command line
• Supports programming & servers
• Community support

5. How Linux Accesses Files

Linux uses an inode‑based file system, where every file has:

• inode number
• file type
• file permissions
• owner & group
• size
• storage location

Linux treats everything as a file, including:

• devices
• directories
• processes
• sockets

6. Linux Standard Directories

7. Basic File & Directory Commands

8. Creating & Viewing Files using cat

cat > file.txt        # create
cat file.txt          # view

9. File Comparison Commands

• cmp file1 file2 – compare byte‑by‑byte
• comm file1 file2 – compare line‑by‑line

10. Disk Related Commands

• df -h – show disk free space
• du -sh folder – folder size
• mount – mount disk
• umount – unmount disk

UNIT – II : Shells, Processes, Pipes, Filters, Scheduling & VI Editor

1. Understanding Shells

A shell is a command interpreter. Popular shells:

• Bash (default)
• Zsh
• Ksh
• Tcsh

2. Processes in Linux

A process = program in execution. Common commands:

ps        # show processes
top       # live monitoring
kill PID  # terminate
jobs      # show background jobs

3. Connecting Processes with Pipes

ls | wc -l

Pipes send output of one command to input of another.

4. Input / Output Redirection

5. Help Commands

• man command
• help command
• info command

6. Background Processing

command &
jobs
bg %1
fg %1

7. Managing Multiple Processes

• ps
• pgrep
• htop
• kill

8. Changing Process Priority

nice -n 10 program
renice 5 PID

9. Scheduling Commands

Using cron

crontab -e

Using at

at 5pm

10. File & Utility Commands

11. VI / VIM Editor

Modes

• Command mode
• Insert mode
• Last‑line mode

Useful commands

i      " insert
x      " delete char
:w     " save
:q     " quit
:wq    " save & quit
/text  " search text

12. Simple Filter Commands

• pr
• head
• tail
• cut
• paste
• sort
• uniq
• tr

13. Regular Expression Filters

• grep – search patterns
• egrep – extended grep
• sed – search & replace

Example:

sed 's/old/new/g' file.txt

UNIT – III : Shell Programming & System Administration Basics

1. Introduction to Shell Programming

A shell script is a text file containing Linux commands.

Example:

#!/bin/bash
echo "Hello Linux"

Run:

chmod +x script.sh
./script.sh

2. Shell Programming Concepts

Variables

name="Abhishek"
echo $name

Conditions

if [ $a -gt 10 ]; then
  echo "OK"
fi

Loops

for i in 1 2 3; do echo $i; done

Functions

hello(){ echo "Hello"; }

3. System Administration Tasks

• User management
• Disk management
• Network setup
• Package installation
• Backup & restore
• System monitoring

4. Configuration & Log Files

Logs are stored in:

/var/log/

Important files:

• /etc/passwd
• /etc/shadow
• /etc/fstab
• /etc/hosts

5. Linux Installation Process

• Boot from USB/DVD
• Create partitions
• Install base system
• Install bootloader
• Reboot

6. System Startup / Shutdown

shutdown -h now
reboot
systemctl reboot

UNIT – IV : User Management, File System, Permissions & Networking

1. Managing User Accounts

Add user

useradd username
passwd username

Delete user

userdel username

2. Permissions & Ownership

Permission types

• Read (r)
• Write (w)
• Execute (x)

Change permissions

chmod 755 file

Change owner / group

chown user file
chgrp group file

3. Managing Groups

groupadd group
groupdel group

4. Disable User Account

usermod -L user

5. Creating & Mounting File System

mkfs.ext4 /dev/sdb1
mount /dev/sdb1 /mnt

6. Super User (su / sudo)

su
sudo command

7. Backup & Restore

• cp
• rsync
• tar
• scp

8. Installing & Removing Packages

Ubuntu/Debian

apt install package
apt remove package

RHEL/CentOS

yum install package
yum remove package