Introduction
Most Linux servers run background services such as web servers, databases, APIs, and monitoring tools. These services need to start automatically, restart when they fail, and be managed consistently.
Modern Linux distributions use systemd as their service manager. It provides a standard way to start, stop, restart, and monitor applications running in the background.
Whether you're deploying a .NET application, a Python API, or a Node.js service, understanding systemd is an important skill for managing production servers.
In this tutorial, you'll learn how to create and manage custom systemd services.
What Is systemd?
systemd is a system and service manager used by most modern Linux distributions.
Its responsibilities include:
Example services:
Nginx
MySQL
Redis
ASP.NET Core API
These services are typically managed through systemd.
Checking Service Status
To view the status of a service:
sudo systemctl status nginx
Example output:
Active: active (running)
This command shows:
Service status
Process ID
Recent logs
Startup information
Starting and Stopping Services
Start a service:
sudo systemctl start nginx
Stop a service:
sudo systemctl stop nginx
Restart a service:
sudo systemctl restart nginx
Reload configuration:
sudo systemctl reload nginx
These commands are commonly used during deployments.
Creating a Custom Service
Suppose you have a .NET application.
Application location:
/var/www/myapi
Executable:
MyApi.dll
Create a service file:
sudo nano /etc/systemd/system/myapi.service
Service File Example
Add the following configuration:
[Unit]
Description=My ASP.NET Core API
[Service]
WorkingDirectory=/var/www/myapi
ExecStart=/usr/bin/dotnet /var/www/myapi/MyApi.dll
Restart=always
User=www-data
[Install]
WantedBy=multi-user.target
Save the file.
This tells systemd how to run your application.
Understanding Service File Sections
Unit Section
[Unit]
Description=My ASP.NET Core API
Provides information about the service.
Service Section
[Service]
ExecStart=/usr/bin/dotnet MyApi.dll
Defines how the service runs.
Install Section
[Install]
WantedBy=multi-user.target
Allows automatic startup during boot.
Reload systemd
After creating or modifying a service:
sudo systemctl daemon-reload
This reloads systemd configuration files.
Enable Auto Startup
Enable the service:
sudo systemctl enable myapi
Output:
Created symlink
The application now starts automatically when the server boots.
Start the Service
Start the custom service:
sudo systemctl start myapi
Check status:
sudo systemctl status myapi
If everything is configured correctly:
Active: active (running)
View Service Logs
systemd integrates with the journal.
View logs:
journalctl -u myapi
View live logs:
journalctl -u myapi -f
This is extremely useful for troubleshooting.
Automatic Service Restart
One of systemd's most useful features is automatic recovery.
Example:
Restart=always
If the application crashes:
Application Crash
↓
systemd Detects Failure
↓
Service Restarts
This improves application availability.
Real-World Example
Suppose you're hosting an ASP.NET Core API.
Without systemd:
Manual Start
↓
Server Reboot
↓
Application Offline
With systemd:
Server Reboot
↓
systemd Starts Service
↓
Application Online
This makes deployments more reliable.
Common Mistakes
Forgetting daemon-reload
After modifying service files:
sudo systemctl daemon-reload
must be executed.
Incorrect File Paths
Verify:
WorkingDirectory
ExecStart
Incorrect paths are a common cause of failures.
Running as Root Unnecessarily
Instead of:
User=root
Use a dedicated application user whenever possible.
This improves security.
Best Practices
When using systemd:
Use dedicated service accounts.
Enable automatic restart.
Store logs properly.
Use descriptive service names.
Monitor service health.
Keep service files under version control when possible.
These practices improve maintainability and reliability.
Conclusion
systemd is the standard service manager for modern Linux systems and an essential tool for running production applications. It simplifies service management by providing commands for starting, stopping, monitoring, and automatically restarting applications.
Whether you're hosting ASP.NET Core APIs, Python services, Node.js applications, or background workers, systemd ensures your applications remain available and start automatically after system reboots. Learning how to create and manage custom services is a valuable skill for developers working with Linux servers.
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