sudo (superuser-do) command

sudo stands for superuser do — it lets you run commands with admin (root) privileges.

Usage

sudo apt update

• Executes command with elevated permissions

Usecases

• Install packages
• Modify system files
• Manage services
• have highest power or permissions of the system

Why

• Protects your system from accidental changes
• Grants controlled access to powerful operations

Careful

• Can modify or break your system
• Always know what you’re running

Pro tip :)

• sudo is power with responsibility — use it intentionally, not casually.
• Use sudo only when necessary — it runs commands as root.

df (disk-free) command

df stands for disk free — it shows available and used disk space on your system.

Usage

df

• Displays disk usage for all mounted filesystems

Usecases

1. Human-readable format:

df -hg

2. Check specific path:

df -h /home

Why

• Monitor disk usage
• Avoid running out of storage
• Useful in servers & deployments

Pro tip :)

• Always use -h for readability — raw bytes aren’t practical.
• Use df to quickly check your system’s storage health.

du (disk-usage) command

du stands for disk usage — it shows how much space files and directories are using.

Usage

du

• Displays size of files/folders in current directory

Usecases

1. Human-readable:

du -h

2. Total size of a folder:

du -sh folder/

3. Sort largest files:

du -h | sort -hr

Why

• Find large files/folders
• Clean up disk space
• Debug storage issues

Pro tip :)

• Use du -sh * to quickly see what’s taking space.
• Use du to track what’s eating your disk.

df v/s du

• df → Shows disk space available (filesystem level)
• du → Shows space used by files/folders (directory level)

Lament example or real world

• df = “How full is my disk?”
• du = “What is filling my disk?”

vi / vim command

• vi → basic text editor
• vim → Vi Improved (more powerful version)

Used to create and edit files directly in terminal

Open a file

vim file.txt

Different modes

1. Normal mode → navigate
2. Insert mode → type text (i)
3. Command mode → save/quit (:)

Commands most common ones

• i → start typing
• Esc → exit insert mode
• :w → save
• :q → quit
• :wq → save & quit
• :q! → quit without saving

Why

• Works everywhere (servers, SSH, minimal systems)
• Fast and keyboard-driven
• Essential for dev & DevOps workflows

Pro tip :)

• Vim feels hard at first, but once it clicks — it’s insanely fast.
• Learn Vim once, use it everywhere.

head command

head is used to display the first few lines of a file (default: 10 lines).

Usage

head file.txt

• shows first 10 lines

Usecases

1. Show specific number of lines:

head -n 5 file.txt

2. Use with pipes:

cat file.txt | head

Why

• Quickly inspect large files
• Useful for logs & debugging

Pro tip :)

• Pair head with tail to explore files efficiently.
• Use head to peek at the beginning of files instantly.

tail command

tail shows the last few lines of a file (default: 10 lines).

Usage

tail file.txt

• Shows last 10 lines

Usecases

1. Show specific lines:

tail -n 5 file.txt

2. Live logs (real-time updates):

tail -f app.log

head & tail together

head -n 20 file.txt | tail -n 10

• Gets lines 11–20

Why the combo

• Quickly slice parts of large files
• Useful for logs, debugging, data inspection

Pro tip :)

• head trims from top, tail trims from bottom — together they isolate exactly what you need.
• Use tail for the end, combine with head for precision.

diff command

diff is used to compare two files and show the differences between them.

Usage

diff file1.txt file2.txt

• Shows what lines were added, removed, or changed

Common Usecases

1. Side-by-side comparison:

diff -y file1.txt file2.txt

2. Ignore whitespace:

diff -w file1.txt file2.txt

Why

• Track changes in files
• Debug differences
• Core concept behind version control (like Git)

Pro tip :)

• diff is the foundation of how tools like Git detect changes.
• Use diff to instantly spot what changed.

locate command

locate is used to quickly search files by name using a pre-built database.

Usage

locate file.txt

• Finds all paths matching file.txt

Usecases

1. Case-insensitive search:

locate -i file.txt

2. Limit results:

locate -n 5 file.txt

Uses a database (not real-time search) Update it with:

sudo updatedb

Why

• Much faster than find
• Great for quick lookups

Pro tip :)

• locate is fast because it searches an index, not the filesystem.
• Use locate for speed, find for accuracy.

find command

find is used to search files and directories in real-time based on name, type, size, etc.

Usage

find . -name "file.txt"

• Searches current directory (.) for file.txt

Usecases

1. Case-insensitive search:

find . -iname "file.txt"

2. Find by type:

find . -type f      # files
find . -type d      # directories

3. Find and delete:

find . -name "*.log" -delete

Why is important

• Real-time, accurate search
• Extremely powerful with filters
• Essential for automation & scripting

Pro tip :)

• find is slower than locate, but always up-to-date and precise.
• Use find when accuracy matters.