Linux for DevOps (Beginners)
1. Linux Fundamentals
1.1 What is Open Source?
Open-source software is software whose source code is freely available for anyone to view, modify, and distribute. Linux is built on open-source principles.
- Source code is publicly accessible
- Community-driven development and contributions
- Free to use, modify, and redistribute
Examples: Linux, Python, Firefox, Android
1.2 What is Linux?
Linux is a free, open-source operating system kernel created by Linus Torvalds in 1991. It powers everything from smartphones to supercomputers.
- Linux is technically a kernel, not a full OS
- Full OS = Linux Kemel + GNU tools + package manager + desktop environment
- Popular distributions (distros): Ubuntu, Fedora, Debian, CentOS, Arch Linux
- Used in servers, cloud, Android, loT, supercomputers
1.3 Linux vs UNIX
Linux =Free, open-source, kemel by Linus Torvalds (1991)
UNIX = Proprietary OS from Bell Labs (1969), not free
macos = UNIX-based (BSD), proprietary by Apple
Similarity = Both follow POSIX standards; Linux was inspired by UNIX
1.4 Why Use Linux?
- Free and open source - no licensing costs
- Highly secure - fewer viruses, strong permission model
- Stable and reliable - servers run for years without reboots
- Lightweight- runs on old hardware
- Industry standard - most servers, cloud, and DevOps tools run on Linux
- Customizable - choose your own components and desktop
1.5 Linux vs Windows
Cost => Linux is free; Windows requires a license
Security => Linux is free; Windows requires a license
Usage => Linux dominates servers; Windows dominates desktops
CLI => Linux is CLI-first; Windows is GUI-first
File System = > Linux: ext4, XFS; Windows: NTFS, FAT32
Software => Linux uses package managers; Windows uses installers (.exe)
1.6 What is a Kernel?
The kernel is the core of the operating system. It manages hardware resources and allows
software to communicate with hardware.
- Manages CPU, memory, and I/O devices
- Provides system calls for programs to request services
- Acts as a bridge between applications and hardware
- Linux kernel is monolithic - all kernel services run in kemel space
Installing Ubuntu via WSL (Windows Subsystem for Linux)
WSL lets you run a Linux terminal directly on Windows without a VM.
- Open PowerShell as Administrator
- Run: wsl -- install
- Restart your PC
Open Ubuntu from the Start Menu
- Set username and password on first launch
Useful WSL commands:
ws1 -- list -- verbose
wsl -- set-default-version 2
# Open Linux files in Windows Explorer
# List installed distros
# Use WSL 2
explorer.exe .
3. Basic Terminal Commands
3.1 Navigation
pwd
Print Working Directory - shows current location
1s
List files and directories
1s -la
List all files (including hidden) with details
od <dir>
Change directory
cd ..
Go up one directory level
cd ~
Go to home directory
cd /
Go to root directory
3.2 File and Directory Operations
mkdir <name>
Create a new directory
mkdir -p a/b/c
Create nested directories
touch <file>
Create an empty file or update timestamp
rm <file>
Remove a file
rm -r <dir>
Remove directory and contents recursively
rm -zf <dir>
Force remove without prompts (use carefully!)
cp <src> <dst>
Copy a file
mv <arc> <dst>
Move or rename a file
cat <file>
Display file contents
less <file>
Scroll through file contents
nano <file>
Open file in nano text editor
vim <file>
Open file in vim text editor
3.3 File Permissions - chmod
Linux file permissions control who can read, write, or execute files.
Permission format: rwxrwxrwx (owner / group / others)
r=4
Read permission
w= 2
Write permission
x= 1
Execute permission
chmod 755 file
Owner: rwx, Group: r-x, Others: r-x
chmod 644 file
Owner: rw-, Group: r-, Others: r-
chmod +x file
Add execute permission for all
chmod -w file
Remove write permission
3.4 Links
Links allow multiple references to the same file.
ln <src> <link>
Create a hard link - points to same inode
ln -s <src> <link>
Create a soft (symbolic) link - like a shortcut
alias 11='1s -la'
Create a command alias (session only)
Key difference: Deleting the original breaks a soft link but NOT a hard link.
4. File Handling & Text Processing
4.1 head & tail
head <file>
Show first 10 lines of a file
head -n 20 <file>
Show first 20 lines
tail <file>
Show last 10 lines
tail -f <file>
Follow file in real-time (great for logs)
4.2 wc -Word Count
we <file>
Show lines, words, and bytes
wc -1 <file>
Count lines only
wc -w <file>
Count words only
wc -c <file>
Count bytes/characters only
4.3 sort
sort <file>
Sort lines alphabetically
sort -r <file>
Sort in reverse order
sort -n <file>
Sort numerically
sort -u <file>
Sort and remove duplicates
sort -k2 <file>
Sort by the 2nd column
4.4 grep - Search Text
grep searches for patterns in files or output.
| grep 'pattern' file | Search for pattern in file |
| grep -i 'pattern' file | Case-insensitive search |
| grep -r 'pattern' dir/ | Recursive search in directory |
| grep -n 'pattern' file | Show line numbers with results |
| grep -v 'pattern' file | Show lines that do NOT match |
| grep -c 'pattern' file | Count matching lines |
| grep -E 'pllp2' file | Extended regex - match p1 OR p2 |
