Top 50 Commands You Must Know for the LFCS Exam in 2025

Objective

Preparing for the Linux Foundation Certified System Administrator (LFCS) exam can feel exciting yet slightly intimidating. Unlike theory based tests, the LFCS focuses entirely on practical skills. You must be able to work comfortably in a Linux terminal and perform real administrative tasks under time pressure. To help you succeed, this guide covers the 50 most important commands for the LFCS exam. They are organized by category with simple explanations and examples to make your practice easier and faster.

Master these and you will be prepared for nearly every scenario the exam can present.

1. File and Directory Management

These commands form the core of daily Linux work. You will use them constantly during the LFCS exam.

• pwd:
  • Displays the full path of the directory you are currently in.
• ls:
  • Lists files and directories. Use ls -l for details and ls -a for hidden files.
• cd:
  • Moves you into another directory. Example: cd /etc.
• touch:
  • Creates an empty file or updates a file timestamp.
• mkdir:
  • Creates directories. Example: mkdir project.
• rmdir:
  • Removes empty directories only.
• rm:
  • Deletes files or directories. Use rm -r for recursive removal.
• cp:
  • Copies files or folders. Example: cp file.txt /tmp/.
• mv:
  • Moves or renames files. Example: mv old.txt new.txt

Hands-on Lab: File and Directory Management

2. File Viewing and Text Editing

You must be comfortable reading and editing files quickly during the exam.

• cat:
  • Displays an entire file on the terminal.
• less:
  • Views large files one page at a time.
• head:
  • Shows the first lines of a file.
• tail:
  • Shows the last lines. tail -f is commonly used for logs.
• nano:
  • Beginner friendly text editor. Perfect for quick edits.
• vim:
  • Advanced editor with powerful features. Commonly required in the exam environment.
• echo:
  • Prints text or writes text to a file. Example: echo test > file.txt.

Hands-on Lab: Text Editing

3. Documentation and Help

You are not expected to memorize everything. These tools help you find answers quickly.

• man:
  • Shows manual pages for commands.
• info:
  • Displays detailed documentation in a different format.
• which:
  • Shows the location of a command's executable.
• whereis:
  • Find binary, source and man page locations.

Hands-on Lab: Command Line Fundamentals

4. Searching and Text Processing

LFCS exam tasks often require filtering logs and processing text files.

• find:
  • Searches for files based on name, type or location.
• locate:
  • Searches quickly using a built database.
• grep:
  • Searches for matching text inside files. Example: grep error /var/log/messages.
• wc:
  • Counts words, bytes and lines.
• sort:
  • Sorts lines alphabetically or numerically.
• uniq:
  • Removes duplicate lines.
• cut:
  • Extracts specific fields or columns from text.
• awk:
  • Processes structured text. Commonly used for reports and data extraction.
• sed:
  • Edits text streams, such as replacing words automatically.

Hands-on Lab: Text Processing

5. Archiving and Compression

You will definitely encounter compressed files during the exam.

• tar:
  • Creates or extracts archive files.
• gzip:
  • Compresses files into .gz format.
• gunzip:
  • Decompresses .gz files.

Hands-on Lab: Archiving and Compression

6. Disk, Filesystem and Memory Management

System storage and memory monitoring are essential skills for LFCS.

• df:
  • Shows disk usage of mounted filesystems.
• du:
  • Shows directory space usage. Example: du -sh /var.
• free:
  • Displays memory and swap usage.
• lsblk:
  • Shows block devices like disks and partitions.
• blkid:
  • Displays UUIDs and filesystem types.
• mount:
  • Mounts filesystems manually.
• umount:
  • Unmounts filesystems.
• mkfs:
  • Creates a filesystem on a partition. Example: mkfs.ext4 /dev/sdb1.
• swapon:
  • Enables swap space.
• swapoff:
  • Disables swap space.

7. Process Control and System Monitoring

You must understand what processes are running and how to stop or analyze them.

• top:
  • Real time system process monitoring.
• htop:
  • Enhanced version of top if installed.
• ps:
  • Lists running processes.
• kill:
  • Stops a process using its PID.
• killall:
  • Stops processes by name.
• nice:
  • Runs a command with modified priority.
• uptime:
  • Shows system running time and load averages.

8. User and Group Management

LFCS exams heavily test user and group tasks.

• useradd:
  • Creates a new user account.
• usermod:
  • Modifies an existing user.
• userdel:
  • Removes a user account.
• passwd:
  • Changes a user password.
• groupadd:
  • Creates a group.
• groupdel:
  • Deletes a group.
• groupmod:
  • Modifies a group.
• id:
  • Displays usernames, groups and IDs.
• chmod:
  • Changes file permissions.
• chown:
  • Changes file ownership.
• chgrp:
  • Changes group ownership.

9. Service Management and Scheduling

You will configure and troubleshoot services during the exam.

• systemctl:
  • Controls and manages system services.
• service:
  • Legacy commands are still useful for some services.
• journalctl:
  • Views system logs from systemd journal.
• crontab:
  • Schedules recurring tasks.
• at:
  • Schedules one time tasks.

10. Networking and Remote Access

Linux servers depend heavily on networking. These commands are required knowledge for LFCS.

• ip:
  • Shows and configures network interfaces.
• ping:
  • Tests network connectivity.
• ss:
  • Displays active sockets and connections.
• curl:
  • Transfers data from URLs and tests endpoints.
• scp:
  • Copies files securely between systems.
• hostnamectl:
  • Views or changes the hostname.

Practice Tips for LFCS Success

• Practice every day and use these commands repeatedly until they become second nature.
• Use a virtual machine or cloud server so you can experiment without fear of breaking anything.
• Combine commands using pipes, for example: cat /var/log/messages | grep ssh.
• Build small tasks like creating users, configuring services and manipulating files to simulate real exam scenarios.

Conclusion

These 50 commands represent the most important tools for the LFCS exam and for real world Linux administration. By practicing them regularly, you develop the confidence and hands on skill required to pass the LFCS and manage Linux systems effectively. If you want guided labs, exam focused exercises and expert tips, learning platforms such as LINUXCERT.GURU can help you master LFCS concepts faster and more efficiently.