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Linux Essentials

Practical tools and commands for managing and debugging a Linux system.

Process Management​

  • ps: Display information about active processes.
    • ps aux: Detailed list of all processes.
  • top / htop: Real-time process monitor.
  • kill: Send a signal to a process (e.g., kill -9 <PID>).
  • nice / renice: Adjust the priority of a process.

File System & Disk​

  • ls: List directory contents (e.g., ls -lah).
  • df / du: Check disk space usage.
  • chmod / chown: Change file permissions and ownership.
  • mount / umount: Attach and detach file systems.
  • ln: Create links (symbolic or hard).

Networking​

  • curl / wget: Download files and interact with APIs.
  • ip / ifconfig: Manage network interfaces and IP addresses.
  • netstat / ss: List active network connections and listening ports.
  • tcpdump / wireshark: Capture and analyze network packets.

Shell Scripting​

  • bash: The standard Linux shell.
  • Pipes (|): Chain multiple commands together (e.g., cat logs.txt | grep "ERROR").
  • Redirection (>, >>, <): Control the input/output of a command.
  • Environment Variables: Store configuration values (e.g., $PATH, $USER).

System Management​

  • systemd / systemctl: The standard init system for managing system services.
    • systemctl start <service>: Start a service.
    • systemctl status <service>: Check the status of a service.
  • journalctl: View and manage system logs.

Performance & Debugging​

  • perf: A powerful profiling tool that can trace hardware and software events.
  • strace: Trace all system calls made by a process.
  • lsof: List all files opened by a process.
  • iotop: Monitor real-time disk I/O usage per process.
  • free: Display total and free memory on the system.