Linux SSH Terminal Commands and Explanations

1. Connection and Authentication

• ssh user@server_ip → Connects to a remote server via SSH.

• ssh -p 2222 user@server_ip → Connects via SSH on a custom port.

2. File and Directory Management

• ls → Lists files and folders in the current directory.

• ls -la → Lists files including hidden ones, with detailed info.

• cd /path → Changes to the specified directory.

• pwd → Prints the full path of the current directory.

• mkdir folder → Creates a new folder.

• rm file → Deletes a file.

• rm -rf folder → Forcefully deletes a folder and its contents.

• cp source target → Copies a file or folder.

• mv source target → Moves or renames a file or folder.

3. Viewing and Editing Files

• cat file.txt → Displays the contents of a file.

• more file.txt → Views a file page by page.

• less file.txt → Allows scrolling through file content.

• nano file.txt → Opens file with a simple text editor.

• vim file.txt → Opens file with an advanced text editor.

4. System Info and Monitoring

• uname -a → Displays system information.

• top → Shows real-time CPU and memory usage.

• htop → Colorful and interactive system monitor (requires installation).

• df -h → Shows disk usage in human-readable format.

• du -sh /folder → Shows the size of a specified folder.

• free -h → Displays RAM usage.

• uptime → Shows how long the server has been running.

5. User and Permission Management

• whoami → Shows the current user.

• id → Displays user ID and group info.

• sudo command → Runs a command with admin privileges.

• adduser username → Adds a new user.

• passwd username → Changes a user's password.

6. Network Commands

• ip a → Lists IP addresses and network interfaces.

• ping google.com → Tests internet connectivity.

• curl URL → Fetches data from a URL.

• wget URL → Downloads files from a URL.

• netstat -tulnp → Lists open ports and associated services.

• ss -tulnp → Modern tool to check active ports and services.

7. Package Management (Debian/Ubuntu)

• apt update → Updates package lists.

• apt upgrade → Upgrades all installed packages.

• apt install package → Installs a package.

• apt remove package → Removes a package.

8. Package Management (CentOS/RHEL/AlmaLinux)

• yum update or dnf update → Updates system packages.

• yum install package → Installs a package.

• yum remove package → Removes a package.

9. Service Management

• systemctl start service → Starts a service.

• systemctl stop service → Stops a service.

• systemctl restart service → Restarts a service.

• systemctl status service → Shows the service status.

• systemctl enable service → Enables the service to start at boot.

10. Other Common Commands

• history → Lists previously used commands.

• clear → Clears the terminal screen.

• tar -czvf archive.tar.gz folder → Compresses a folder into an archive.

• tar -xzvf archive.tar.gz → Extracts an archive.

• chmod 755 file → Changes file permissions.

• chown user:group file → Changes file ownership.