How to start, stop and restart services in Linux

For advanced Linux users, starting, stopping and restarting Linux services is essential. These operations allow users to access the functionality of each service. For example, to use a web server, users must start the Apache service, or to use a database, users must start the MySQL service. Managing Linux services is also important for system stability and can help improve system performance.

Despite common belief, starting, stopping, and restarting services on Linux is relatively simple. We will be working with Linux, but all commands to start, stop and restart Linux services can be run on CentOS, Ubuntu, Redhat, Fedora, Debian and many other distributions.

What is the difference between systemctl and service commands?

There are two official management tools that provide a consistent way to start, stop, restart, and manage system services on Linux:

Systemctl offers more advanced features, including dependency management, enabling/disabling services, and integration with journalctl for logging. The service is simpler and is mainly used for basic start, stop, and service status commands. Often used with older SysVinit-based systems.

Which one you use will depend on whether your distribution uses systemd or init. Most modern distributions now use systemd, so systemctl is the preferred service manager. But some old habits are hard to eradicate, so many managers still cling to the old service command.

Fortunately, the systemd developers made sure to preserve the service and redirect it to systemctl, so even on systemd-based systems, using the service will still work for basic tasks.

To complicate matters further, you may have installed a random service that has not been updated to either the service or the systemctl tools and you need to start it manually with /etc/rc.d (or /etc/init.d). But we're looking for best practices here, and to start, stop, or restart applications on Linux, best practices begin and end with systemctl.

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Start a Linux service

Let's say you want to start the Apache server.

To do this:

1. Open a terminal window.
2. Run the command sudo systemctl start httpd.

In this command:

• sudo tells Linux that you are running the command as root.
• systemctl manages system services.
• start tells the systemctl command to start the Apache service.
• httpd is the name of the Apache web server service.

3. Once you run the command, you will receive the following message:

The service httpd has started successfully.

Note If the service is already running you will see the following message:

The service httpd is already running.

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Common error messages

Failed to start httpd.service. Unit httpd.service not found.

This error occurs if the Apache web server package is not installed or the service unit file is missing. Install the Apache package using sudo apt install apache2 (on Debian-based systems) or sudo yum install httpd (on Red Hat-based systems) to resolve it.

Failed to start httpd.service. Address already in use.

This indicates that another process is already using the port Apache wants to connect to (typically port 80). Identify the conflicting process with sudo lsof -i:80 and stop it, or change the port settings in the Apache configuration file.

Stop a Linux service

To stop the Apache service:

1. Open a terminal window
2. Run the command sudo systemctl stop httpd.
3. You should now see the following message:

The service httpd has been stopped successfully.

Note that if the service, in this case Apache, was not running, you will receive the following message:

Failed to stop service httpd. Unit httpd.service is not loaded.

Install it using sudo apt install apache2 (based on Debian) or sudo yum install httpd (Based on Red Hat).

Or you may receive one of the following messages:

Failed to stop service httpd. Unit httpd.service is not running.

This indicates that Apache is already stopped, so no action is required.

Failed to stop service httpd. Unit httpd.service is in a failed state.

This suggests that Apache encountered an error and is in a failed state. To troubleshoot, run sudo journalctl -xe to view detailed logs, then try restarting the service.

Failed to stop service httpd. Unit httpd.service is locked.

This error occurs if another process is controlling the service. Wait briefly and try again, or check for running management tasks with ps aux | grep httpd to identify the blocking process.

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Restart a Linux service

To restart the same service (Apache):

1. Open a terminal window.
2. Run the command sudo systemctl restart httpd.
3. The service will restart and return to the bash prompt.
4. You will receive the following message:

The service httpd has been restarted successfully.

Common error messages

If the Apache service is not running, you will see the following output:

The service httpd is not running.

You can start it directly with sudo systemctl start httpd or check your status with systemctl status httpd.

You can also see the following:

Job for httpd.service failed.

This usually indicates a configuration or dependency issue. To troubleshoot, review the error details with sudo journalctl -xe and correct any configuration problems.

Start, stop and restart services with the use of the service

To make things interesting, the service command still works, even for those distributions that have migrated to systemd and systemctl. This means that those who instinctively type service when they need to restart a service on Linux will not receive a Unknown command mistake.

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In the case of service, the command will redirect to systemctl. In fact, when you run the service command on a systemctl-enabled distribution, you will clearly see the redirect information.

The use of the service command is a little different from that of systemctl. The service name and start, stop, and restart options change:

sudo service httpd start
sudo service httpd stop
sudo service httpd restart

In each case, you will see the service redirected to systemctlbut the service you try to start, stop or restart will succeed.

To learn more about what systemctl can do for you, be sure to run the systemctl man command and read the man page.