Essential Linux Commands

If you’re preparing for Linux certifications like LFCS, RHCSA, or CompTIA Linux+, then mastering the Linux command line is non-negotiable. These exams are hands-on and expect you to be fluent with the terminal.

This guide compiles the essential Linux commands you must know—organized by category, explained simply, and packed with examples to help you practice and pass your exam.

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📁 File and Directory Management

ls         # List files
cd         # Change directory
pwd        # Show current path
mkdir      # Make directory
rm         # Remove files/directories
cp         # Copy files
mv         # Move or rename
find       # Search for files

✅ Example:

find /var -name "*.log"

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🔧 File Permissions & Ownership

chmod      # Change file permissions
chown      # Change file owner
groups     # Show group memberships
umask      # Default permissions for new files

✅ Example:

chmod 755 script.sh
chown user:group file.txt

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📦 Package Management

Debian-based (Ubuntu, Debian)

apt update && apt upgrade
apt install nginx
apt remove nginx

RHEL-based (Rocky, CentOS, AlmaLinux)

dnf install nginx
yum remove httpd
dnf update

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👥 User and Group Management

useradd     # Create user
passwd      # Set password
usermod     # Modify user
userdel     # Delete user
groupadd    # Add group
id          # Show user ID

✅ Example:

useradd devuser
passwd devuser
groupadd developers
usermod -aG developers devuser

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📆 Scheduled Tasks

crontab -e       # Edit user’s cron jobs
at now + 5 min   # Run task once
systemctl list-timers  # View timers

✅ Example:

crontab -l

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🔥 System Services (systemd)

systemctl status sshd
systemctl start nginx
systemctl enable nginx
systemctl stop firewalld

✅ Example:

systemctl restart network

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🌐 Networking

ip a                # Show IP addresses
ip r                # Show routes
ping google.com     # Test connection
hostnamectl set-hostname web1

✅ Example:

nmcli dev show

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📂 Disk & Storage

df -h        # Show disk usage
du -sh *     # Folder sizes
mount        # Mount device
lsblk        # List block devices
fdisk -l     # Partition info

✅ Example:

mkfs.ext4 /dev/sdb1
mount /dev/sdb1 /mnt/data

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🛠️ Process & System Monitoring

top          # Real-time system monitor
ps aux       # List running processes
kill         # Terminate process
htop         # Enhanced top (install separately)
uptime       # System uptime
free -m      # Memory usage

✅ Example:

kill -9 1234

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🧪 Bash Scripting Basics

#!/bin/bash
for file in *.txt; do
  echo "Found $file"
done

✅ Useful CLI tools:

echo, tee, awk, sed, cut, grep, basename, dirname

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Internal Links

• Shell Scripting Basics for LFCS
• Linux File Permissions Guide
• Set Up a Linux Lab

External Links

• Linux Foundation Training Portal
• ExplainShell – Command Explainer

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FAQ

Do I need to memorize all these commands?

No—but you should be comfortable using them under pressure in real scenarios.

Are these commands used in all Linux exams?

Yes. The majority of certification tasks require strong command-line familiarity.

What’s the best way to practice commands?

Use a practice lab (like VirtualBox) and challenge yourself to complete daily tasks without a GUI.

Can I use command help during the exam?

Some exams allow access to man pages and --help flags, but you still need to know the basics.

 

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Call to Action

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