As a DevOps engineer, mastering Linux commands is fundamental for managing infrastructure, automating tasks, and ensuring seamless deployments. This blog highlights critical Linux command categories that every DevOps professional should know.
1. Process Management
Process management is vital for controlling and monitoring applications running on Linux systems. Here are essential commands:
Key Commands and Their Usage:
List processes:
ps aux # Shows all running processes
ps -ef # Alternative format for process listing
ps -u username # Processes for a specific user
Process monitoring:
top # Interactive process viewer
htop # Enhanced version with color coding and mouse support
Process control:
kill PID # Send SIGTERM to terminate a process
kill -9 PID # Forcefully terminate a process
killall name # Kill all processes by name
Service management:
systemctl start service # Start a service
systemctl stop service # Stop a service
systemctl restart service # Restart a service
Process priority management:
nice -n 10 command # Start command with lower priority
renice -n 10 -p PID # Adjust priority of a running process
2. File System Management
Linux filesystems are organized in a tree structure. Managing files and directories is integral to system administration.
Key Commands and Their Usage:
File permissions:
chmod 755 file # rwx for owner, rx for others
chown user:group file # Change ownership
File searching:
find / -type f -name "*.log" # Find all log files
find / -mtime -7 # Files modified in the last 7 days
Disk usage:
du -sh * # Size of directory contents
df -h # Filesystem usage
3. Network Management
Network configuration and troubleshooting are key DevOps skills.
Key Commands and Their Usage:
Network connectivity:
ip addr # Show IP addresses
ping -c 4 host # Test connectivity with 4 packets
Port monitoring:
netstat -tulpn # Show listening ports and processes
ss -tunlp # Modern alternative to netstat
Network debugging:
tcpdump -i eth0 # Capture packets on a network interface
nmap localhost # Scan open ports
4. System Monitoring
Monitoring system performance ensures reliable operations.
Key Commands and Their Usage:
Resource monitoring:
free -m # Display memory usage in MB
vmstat 1 # Virtual memory stats updated every second
Performance analysis:
perf top # CPU performance analysis
strace command # Trace system calls
5. Log Management
Logs are essential for debugging and auditing system activities.
Key Commands and Their Usage:
System logs:
journalctl -f # Follow system logs
journalctl -u service # View service-specific logs
tail -f /var/log/syslog # Follow the system log
Log analysis:
grep -r "error" /var/log/ # Search for errors in logs
awk '/pattern/ {print $1,$2}' logfile # Extract specific fields
6. Package Management
Managing software packages efficiently is crucial for system updates and deployments.
Key Commands and Their Usage:
For RHEL/CentOS:
yum update -y # Update all packages
yum install package # Install a specific package
For Ubuntu/Debian:
apt update && apt upgrade # Update system
apt install package # Install a package
7. Security Management
Securing systems involves managing user access, monitoring, and hardening configurations.
Key Commands and Their Usage:
User management:
useradd -m username # Create a user with a home directory
passwd username # Set a password for the user
Security monitoring:
last # Show last logins
fail2ban-client status # Display banned IPs
Conclusion
Mastering these Linux commands will enhance your efficiency as a DevOps engineer. They are essential for automation, troubleshooting, and maintaining secure, high-performing systems.
very useful content!