How to Manage Services with Systemd in Fedora

Edited 2 weeks ago by ExtremeHow Editorial Team

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Managing services on modern Linux distributions is important for system administrators and any user who needs to maintain control over the services running on a machine. Fedora, a popular Linux distribution, uses systemd as its system and service manager. This article explains how services can be effectively managed using systemd in Fedora. We'll cover topics such as starting, stopping, enabling, disabling, and checking the status of services, as well as creating custom service units. Whether you're new to Fedora or Linux systems in general, or you're an experienced user who needs a refresher, this comprehensive guide is useful for everyone.

Introduction to systemd

Systemd is a tool that provides a system and service manager designed to replace traditional Unix System V (sysv) and BSD init. It provides on-demand start of daemons, service monitoring, snapshot support, and more. Nicer relies on services. The core of systemd is managed through systemctl command, which is responsible for checking and controlling the state of the systemd system and service manager.

Systemd components

Before we dive into practical usage of systemd, it's helpful to understand its main components:

• Units: The basic building block of systemd - this can be of various types, including service units for managing services.
• Systemctl: The primary command-line utility for interacting with systemd, which is used to control services.
• journalctl: This tool is used to query and display logs from systemd's journal, instead of the traditional logs.

Understanding service units

Service units are the most common type of unit in systemd. These units contain settings that define what the service is, how it should be started or stopped, what it depends on, and other specific behavior.

A service unit file is usually located in /etc/systemd/system or /usr/lib/systemd/system and has the following syntax:

[Unit]
Description=My Sample Service
[Service]
ExecStart=/usr/bin/my-service
ExecStop=/usr/bin/my-service-stop
Restart=on-failure
[Install]
WantedBy=multi-user.target

Each service file typically contains the following sections:

• [unit]: Describes the service and its dependencies.
• [service]: This defines how the service is started.
• [Install]: Provides information for enabling and disabling the service.

Managing services with systemctl

systemctl command is used to monitor and control systemd. Below are common tasks and how you can perform them using systemctl:

Checking the service status

To check the status of a service, use:

systemctl status my-service.service

This command will provide information about the service status, recent logs, and more.

Starting the service

You can use the following to start the service:

systemctl start my-service.service

Starting a service manually doesn't mean it will start automatically upon boot.

Stopping the service

The following command is used to stop a service:

systemctl stop my-service.service

This command stops the service until manually restarted or rebooted.

Restarting the service

To restart a service, use:

systemctl restart my-service.service

This operation stops the service (if it is running) and then starts it again.

Enabling and disabling services

To start a service automatically at system boot, enable it as follows:

systemctl enable my-service.service

Conversely, to disable a service so that it does not start automatically, use:

systemctl disable my-service.service

Enabling a service creates a symbolic link from the service's unit file to the system's boot-up configuration.

Using daemon reload

If you modify a unit file or configuration in the systemd tree, it is often necessary to reload systemd:

systemctl daemon-reload

This command informs systemd to scan for new or modified unit files.

Creating custom service units

Creating a custom service allows you to run your own applications as managed services. Here is a simple step-by-step way to create it:

Step 1: Create the unit file

Open a text editor and create a new service unit file in the /etc/systemd/system/ directory:

sudo nano /etc/systemd/system/my-custom-service.service

Fill it with the required service definition:

[Unit]
Description=Custom Service Example
[Service]
ExecStart=/usr/bin/custom-script.sh
Restart=on-failure
[Install]
WantedBy=multi-user.target

Step 2: Set permissions

Make sure the script or program being called in ExecStart has the proper permissions:

chmod +x /usr/bin/custom-script.sh

Step 3: Reload systemd

After creating the new unit file, reload systemd:

systemctl daemon-reload

Step 4: Start and enable the service

Now start and enable your custom service:

systemctl start my-custom-service.service
systemctl enable my-custom-service.service

Your custom service should now be managed the same as any other system service.

Using systemd targets

Target endpoints are configurations that allow you to abstract the concept of runlevels in traditional init systems. They help manage dependencies between services and other units, providing a way to group multiple services and units together.

Listing available targets

To find out the available targets on your system, use:

systemctl list-units --type=target

Changing the runlevel

To change the target or runlevel, use:

systemctl isolate multi-user.target

This command is equivalent to changing the runlevel to multi-user mode.

Understanding logs with journalctl

Systemd comes with an integrated system journaling tool known as journalctl. This log management tool consolidates the logs of all services managed by systemd into a central repository.

Viewing the log

To view the logs for a specific service, use:

journalctl -u my-service.service

Real-time logging

When monitoring logs in real-time as they are generated, use the following flag:

journalctl -u my-service.service -f

Troubleshooting common problems

There can sometimes be problems in managing services smoothly. Knowing how to troubleshoot can be invaluable:

• Service failure to start: If a service fails to start, examine the log entries for that service using journalctl to identify specific error messages.
• Service dependency issues
: Make sure dependent services are running. Use systemctl list-dependencies command to view the dependencies of a service.
• Permissions: Verify that the script and its associated files or required ports have the correct permissions or ownership.

Conclusion

Efficient management of services is fundamental to system administration in Fedora and other Linux distributions that use systemd. This guide has shown you how to manage various aspects of services using systemctl, from performing basic tasks like starting and stopping services to creating custom service units and handling logs with journalctl. With these skills, you can ensure that your systems run smoothly and efficiently, automate tasks, and handle system services effectively.

Remember that in the Linux world, any action you perform on a system may require root privileges. Make sure you have the proper permissions and always back up important files before making changes to critical system configurations. Understanding systemd and the tools it provides is invaluable for effective Linux service management.

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