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                                                       Linux A2Z tutorial

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🖥️ Top 50 Linux Commands for Beginners

1. File & Directory Management

Command	Description
pwd	Show current directory
ls	List files and directories
cd	Change directory
mkdir	Create a directory
rmdir	Remove empty directory
rm	Remove file/directory
cp	Copy file/directory
mv	Move/rename file/directory
touch	Create empty file
tree	Show directory structure as a tree
find	Search files by name, type, size

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2. Viewing & Editing Files

Command	Description
cat	View file content
tac	View file content in reverse
less	Scroll through file content
more	View file page by page
head	View first lines of a file
tail	View last lines of a file
nano	Simple text editor
vi / vim	Advanced text editor
grep	Search for text inside files
wc	Count lines, words, and characters
diff	Compare two files

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3. Permissions & Ownership

Command	Description
chmod	Change file/directory permissions
chown	Change file owner
chgrp	Change file group
umask	Set default permissions for new files
ls -l	Show detailed list with permissions

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4. System & Hardware Info

Command	Description
uname	Show system info
uname -r	Show kernel version
top	Show running processes
htop	Interactive process viewer (needs install)
df	Show disk space usage
du	Show directory/file size
free	Show RAM usage
uptime	Show system uptime and load
who	Show logged in users
w	Show active users and processes
id	Show user ID and groups
hostname	Show system hostname
lscpu	CPU information
lsblk	Block device information
lspci	PCI devices
lsusb	USB devices

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5. Package Management

(Depends on distro) Ubuntu/Debian: apt Fedora/RedHat: dnf

Command	Description
apt update / dnf check-update	Update package list
apt upgrade / dnf upgrade	Upgrade installed packages
apt install <pkg> / dnf install <pkg>	Install software
apt remove <pkg> / dnf remove <pkg>	Remove software
apt search <pkg> / dnf search <pkg>	Search software

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6. Networking

Command	Description
ping	Test connectivity to a host
ifconfig / ip a	Show network interfaces
curl	Fetch a URL / test HTTP requests
wget	Download files from internet
ssh	Connect to remote machine
scp	Copy files to/from remote machine
netstat / ss	Show network connections
traceroute	Show path to a host

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7. Miscellaneous

Command	Description
echo	Print text to terminal
date	Show current date/time
cal	Show calendar
history	Show command history
alias	Create shortcuts for commands
clear	Clear terminal screen
man	Open manual for a command
sudo	Run commands as root

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✅ Tips for Beginners

1. Use man <command> to learn more about each command.
2. Experiment in a safe directory, e.g., /home/user/test.
3. Combine commands with pipes (|) and redirection (> / >>) as you get comfortable.
4. Start with file navigation, then move to system info, then networking and package management.

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#------------------------------------------------------------------------------ EXTRAS

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🔹 Netstat & SS Tutorial

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1️⃣ netstat (Network Statistics)

netstat is a classic command for displaying network connections, routing tables, interface stats, etc.

Basic Usage

netstat

• Shows all active connections on your system (TCP, UDP, UNIX sockets, etc.)

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Common Options

Option	Description
-a	Show all connections, listening and non-listening
-t	Show only TCP connections
-u	Show only UDP connections
-l	Show only listening ports
-n	Show numeric addresses/ports instead of hostnames
-p	Show process ID and name using the connection
-r	Show routing table
-i	Show network interface stats

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Example: Show all listening TCP ports

netstat -tln

Explanation:

• -t → TCP only
• -l → listening ports
• -n → numeric output

Sample Output:

Proto Recv-Q Send-Q Local Address           Foreign Address         State
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN
tcp6       0      0 :::80                   :::*                    LISTEN

Fields:

• Proto → Protocol (TCP/UDP)
• Recv-Q / Send-Q → Queue sizes for incoming/outgoing data
• Local Address → IP and port on your machine
• Foreign Address → Remote IP and port
• State → Status (LISTEN, ESTABLISHED, TIME_WAIT, etc.)

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Show process using ports

sudo netstat -tulpn

• -t TCP, -u UDP
• -l Listening
• -p Show PID/program name
• -n Numeric

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⚠️ Note:

• On modern Linux, netstat is deprecated in favor of ss.
• net-tools package is needed for netstat on some distributions.

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2️⃣ ss (Socket Statistics)

ss is faster and more powerful than netstat. It can display detailed socket info quickly.

Basic Usage

ss

• Shows all active connections.

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Common Options

Option	Description
-t	TCP connections
-u	UDP connections
-l	Listening sockets only
-n	Show numeric addresses/ports
-p	Show process using socket
-a	All sockets (listening + non-listening)
-s	Summary of socket statistics

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Example: Show all listening TCP ports

ss -tln

Sample Output:

State      Recv-Q Send-Q Local Address:Port  Peer Address:Port
LISTEN     0      128   0.0.0.0:22         0.0.0.0:*
LISTEN     0      128   [::]:80            [::]:*

Fields:

• State → Socket state (LISTEN, ESTAB, TIME-WAIT, etc.)
• Recv-Q / Send-Q → Queue sizes
• Local Address:Port → Your machine’s IP and port
• Peer Address:Port → Remote machine’s IP and port

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Show process using ports

sudo ss -tulpn

• Works exactly like netstat -tulpn
• Shows PID and program name listening or connected

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Summary: netstat vs ss

Feature	netstat	ss
Speed	Slower	Faster
Modern Linux	Deprecated	Recommended
Output	Standard, older format	Cleaner, more detailed
Example for listening ports	netstat -tln	ss -tln

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Practical Tips

1. Use ss -tulpn to check which process is using a port.

2. Use ss -s to get socket summary for debugging network issues.

3. Combine with grep to filter, e.g.,

   ss -tulpn | grep :22

   → Check if SSH is running on port 22

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