Linux 121: Managing Services and Processes on Linux

Managing services and processes is essential for maintaining a healthy and responsive Linux system. In this guide, we'll explore how to start, stop, monitor, and manage both foreground processes and background services effectively.

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1. Understanding Processes and Services

• Processes are instances of running programs.

• Services (daemons) are background processes that often start at boot (e.g., sshd, cron, nginx).

Knowing how to control them allows you to maintain uptime, troubleshoot issues, and optimize resource use.

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2. Managing Processes with ps, top, and htop

ps – Snapshot of Running Processes

ps aux

Lists all processes with useful details like PID, CPU, and memory usage.

top – Real-Time Process Monitor

top

Interactive view of system resource usage. Press k to kill a process by PID.

htop – Enhanced Interactive Monitor

Install it if not available:

sudo apt install htop     # Debian/Ubuntu
sudo yum install htop     # RHEL/CentOS

Then run:

htop

Navigate with arrow keys, filter, and kill processes more easily.

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3. Starting, Stopping, and Managing Services

Most modern Linux systems use systemd to manage services via systemctl.

Common systemctl Commands

sudo systemctl start nginx       # Start a service
sudo systemctl stop nginx        # Stop it
sudo systemctl restart nginx     # Restart it
sudo systemctl status nginx      # Check status

Enable or Disable at Boot

sudo systemctl enable nginx      # Start on boot
sudo systemctl disable nginx     # Don’t start on boot

List All Services

systemctl list-units --type=service

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4. Managing Services with init.d and service (Older Systems)

For legacy systems not using systemd:

sudo service apache2 start
sudo service apache2 status

Or directly:

sudo /etc/init.d/apache2 restart

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5. Managing Background and Foreground Processes

Run a Process in Background

./script.sh &

View Background Jobs

jobs

Bring Background Job to Foreground

fg %1

Kill a Background Job

kill %1

Or by PID:

kill 1234

Use kill -9 1234 to forcefully stop if needed.

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6. Using nice and renice to Control CPU Priority

Start with Lower Priority

nice -n 10 command

Change Priority of Running Process

renice -n 5 -p 1234

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7. Monitoring Systemd Services with Logs

Use journalctl to view logs:

sudo journalctl -u nginx        # Logs for nginx
sudo journalctl -xe             # View system logs with errors

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8. Auto-Restarting Services

Create or edit a systemd unit override:

sudo systemctl edit your-service

Then add:

[Service]
Restart=always
RestartSec=3

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9. Conclusion

Process and service management is a critical Linux administration skill. Whether you’re diagnosing issues, optimizing system load, or automating server behavior, knowing how to interact with systemctl, ps, and top will make you significantly more efficient.

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Next in the series:
Linux 122: Using and Managing System Logs on Linux