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Introduction
Linux is the backbone of modern IT infrastructure, powering everything from cloud servers to DevOps pipelines. Mastering essential Linux commands is critical for system administrators, DevOps engineers, and cybersecurity professionals. This guide covers key commands for efficient system management, troubleshooting, and security hardening.
Learning Objectives
- Learn critical Linux commands for system administration and DevOps tasks.
- Understand security-focused commands for hardening Linux systems.
- Master troubleshooting techniques using built-in Linux tools.
1. System Monitoring with `top` and `htop`
Command:
top
Step-by-Step Guide:
- Run `top` in the terminal to view real-time system processes.
- Press `Shift + M` to sort by memory usage.
3. Use `q` to exit.
For a more advanced view, install `htop`:
sudo apt install htop Debian/Ubuntu sudo yum install htop RHEL/CentOS
Then run:
htop
2. Disk Usage Analysis with `df` and `du`
Command:
df -h
Step-by-Step Guide:
1. `df -h` displays disk space usage in human-readable format.
2. For detailed directory-level analysis, use:
du -sh /path/to/directory
3. To find large files (>100MB), run:
find / -type f -size +100M -exec ls -lh {} \;
3. Network Troubleshooting with `netstat` and `ss`
Command:
sudo netstat -tulnp
Step-by-Step Guide:
1. `netstat -tulnp` lists all listening ports and associated processes.
2. For a modern alternative, use `ss`:
ss -tulnp
3. Check active connections with:
ss -s
4. Process Management with `ps` and `kill`
Command:
ps aux | grep nginx
Step-by-Step Guide:
1. `ps aux` lists all running processes.
- Filter for a specific process (e.g., NGINX) using
grep.
3. To terminate a process:
kill -9 [bash]
- File Permissions and Security with `chmod` and `chown`
Command:
chmod 600 /path/to/file
Step-by-Step Guide:
1. `chmod 600` restricts file access to the owner only.
2. To change ownership:
chown user:group /path/to/file
3. Verify permissions with:
ls -l /path/to/file
6. Log Inspection with `journalctl` and `grep`
Command:
sudo journalctl -xe
Step-by-Step Guide:
1. `journalctl -xe` displays system logs with detailed errors.
2. Filter logs for a specific service:
journalctl -u nginx --no-pager
3. Search logs for errors:
grep -i "error" /var/log/syslog
7. SSH Hardening and Key Management
Command:
ssh-keygen -t ed25519
Step-by-Step Guide:
1. Generate a secure SSH key:
ssh-keygen -t ed25519 -a 100
2. Disable root login in `/etc/ssh/sshd_config`:
PermitRootLogin no
3. Restart SSH:
sudo systemctl restart sshd
What Undercode Say
- Key Takeaway 1: Linux commands are foundational for IT efficiency—automate repetitive tasks with scripts.
- Key Takeaway 2: Security hardening (SSH, file permissions) is non-negotiable in production environments.
Analysis:
Linux remains the dominant OS for servers and cloud infrastructure. As DevOps and cybersecurity demands grow, fluency in these commands separates proficient professionals from novices. Future advancements in AI-driven system management may automate some tasks, but deep Linux expertise will remain invaluable.
Prediction:
With the rise of edge computing and containerization, Linux skills will become even more critical. Expect increased integration of AI tools (e.g., log analysis bots), but core command-line proficiency will remain essential.
IT/Security Reporter URL:
Reported By: Kinge Hans – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
