Useful Ubuntu Tips

1. Check Open Ports

To see which ports are being used by your server:

sudo ss -tulnp

Notes:

• 0.0.0.0:* → loopback (safe, local only)
• [::]:* → open to all (public)

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2. Keep the System Updated

Update package lists and upgrade all packages:

sudo apt update && sudo apt upgrade -y

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3. Enable Automatic Security Updates

Install and configure unattended upgrades:

sudo apt install unattended-upgrades
sudo dpkg-reconfigure --priority=low unattended-upgrades

This ensures security updates are applied automatically.

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4. Basic Firewall Setup

Use ufw (Uncomplicated Firewall) to manage firewall rules:

sudo ufw enable
sudo ufw status
sudo ufw allow ssh       # allow SSH access
sudo ufw allow 80/tcp    # allow HTTP
sudo ufw allow 443/tcp   # allow HTTPS

Tip: Always allow SSH before enabling ufw to avoid locking yourself out.

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5. Monitor System Resources

Check CPU, memory, and disk usage:

top           # real-time CPU & memory
htop          # interactive, more user-friendly
df -h         # disk usage
free -h       # memory usage

Install htop if not available:

sudo apt install htop

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6. Manage Services

Check status, start, stop, or restart services:

sudo systemctl status nginx
sudo systemctl start nginx
sudo systemctl stop nginx
sudo systemctl restart nginx
sudo systemctl enable nginx   # start on boot

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7. Check Logs

View system logs for troubleshooting:

journalctl -xe          # system logs
sudo tail -f /var/log/syslog  # live system log

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8. Secure SSH

• Disable root login: edit /etc/ssh/sshd_config → PermitRootLogin no
• Use key-based authentication instead of passwords
• Change default port for SSH (optional)

Restart SSH after changes:

sudo systemctl restart ssh

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9. Fail2Ban for Brute-Force Protection

Install and enable fail2ban:

sudo apt install fail2ban
sudo systemctl enable fail2ban
sudo systemctl start fail2ban

Check status:

sudo fail2ban-client status

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10. Useful Shortcuts

• Ctrl + R → search command history
• !! → repeat last command
• !<number> → run command from history by number
• tmux or screen → keep sessions running after disconnect