Use Systemctl to Manage Services

What is Systemctl?

Systemctl is the central management tool for controlling to the systemd init system. As such, you use
this command most often to interact with the systemd system. Most Linux® distributions use systemd as
their init system, so it helps to be familiar with using the systemctl function when
managing the services running on your Linux system.

Manage services

The following example shows the basic command template for using the systemctl command:

systemctl (command) (service)

This differs from the service command use a service (service) (command) format, which uses commands
such as service httpd reload to reload the Apache service. Using this name example under the systemctl
format, the command looks like the following examples:

CentOS®-based or Red Hat® Enterprise Linux®-based systems:

systemctl reload httpd

Ubuntu operating systems:

systemctl reload apache2

Note: You do not have to include the .service after the name of the service you want to manage.
Systemctl is smart enough to know that you are trying to operate a service when using service management commands.

Following are certain common systemctl commands:

• start: Start a service that is not currently running
• stop: Stop a service currently running
• restart: Restart a currently running service
• reload: Perform a soft restart of a currently running service
• enable: Enable a service to start automatically whenever the system reboots
• disable: Prevent a service from starting automatically when the system reboots
• status: Check the current status of a service on your system

Note: The reload option is not always available. You can use reload-or-restart instead if you are unsure
about reload availability. Using reload-or-restart attempts to use reload first, and uses restart
if reload is not available.

Following are some less common options:

• is-active: Check to see if a unit is currently active (running)
• is-enabled: Check if a service is enabled or disabled
• is-failed: Check if a service is in a failed state
• list-units: Check all the units that systemd currently considers active on the system

The list-units command

The list-units option displays a table with the following columns:

• UNIT: The systemd unit (or service) name
• LOAD: The service currently loaded in systemd
• ACTIVE: A summary of whether the service is currently active
• SUB: Gives a little more detail about the current state of the service
• DESCRIPTION: A short description of what the service is or does

Adding the --all argument to the list-units systemctl command includes any service that systemd
loaded or tried to load regardless of its current state on the system, as shown in the following example:

systemctl list-units --all

You can use the list-units command can be used in a few additional ways, such as adding the --state= filter,
as shown in the following example:

systemctl list-units --all --state=(filter)

Typically, you use this option to filter the results by the service’s current state, either active or inactive,
as shown in the following example:

systemctl list-units --all --state=inactive

You can filter the results further by adding the following argument:

systemctl list-units --type=(filter)

This option tells systemctl to list only the services of the specified type. For example, replacing (filter) with
(service) in the preceding command lists only active service units.

Similarly, you can use the command systemctl list-units-files list every available unit file within the systemd
path, including those that systemd has not tried to load.

The mask command

If you need to prevent a service from starting, manually or automatically, you can use the mask command with systemctl.
For example, suppose you want to make sure Apache® does not run. If you are not running as root, you need to place
the sudo command in front of the command. Otherwise, the command looks similar to the following example:

systemctl mask httpd.service

or

systemctl mask apache2.service

When you want to unmark the service, replace the preceding mask with unmask, and the service can start again.

Conclusion

While there are more advanced uses of the systemctl utility, these are the use options that you will use most often.
You are now familiar with the most common uses of systemctl when interacting with systemd. Systemctl is your
main method of interaction for service management.