Linux service enable disable

Enabling and disabling systemd services

This document applies to the following products and product versions:

• SUSE Linux Enterprise Server 15 SP3, 15 SP2, 15 SP1, 15 GA, 12 SP5, 12 SP4, 12 SP3
• SUSE Linux Enterprise Server for SAP Applications 15 SP3, 15 SP2, 15 SP1, 15 GA, 12 SP5, 12 SP4, 12 SP3
• SUSE Linux Enterprise High Availability Extension 15 SP3, 15 SP2, 15 SP1, 15 GA, 12 SP5, 12 SP4, 12 SP3
• SUSE Linux Enterprise High Performance Computing 15 SP3, 15 SP2, 15 SP1, 15 GA
• SUSE Linux Enterprise Desktop 15 SP3, 15 SP2, 15 SP1, 15 GA, 12 SP5, 12 SP4, 12 SP3
• SUSE Linux Enterprise Real Time 15 SP3, 15 SP2, 15 SP1, 15 GA, 12 SP5, 12 SP4, 12 SP3

2 Enabling and disabling services with systemctl #

systemctl is the systemd command for controlling how services start on a Linux system. A service can be enabled, disabled, or masked, and it can be configured to start at boot, on demand, manually, or prevented from starting under any circumstances.

Enabling a service means it will start at boot. Disabling a service means it will not start at boot, but can be started manually, or as a dependency of another service. Enabling or disabling a running service does not automatically change its current state; if it is running, it will continue to run, and if it is not running, it will not start. When you enable or disable a service, you have the option to stop or start the service with a separate command, or to enable/disable and start/stop with a single command.

A masked service cannot be started by any means, and must be unmasked to be usable.

3 systemctl commands to enable, disable, and mask services #

Check if a service is enabled or disabled.

systemctl status SERVICE-NAME

Check if a service is running, stopped, enabled, or masked, and display the most recent log entries.

systemctl enable SERVICE-NAME

Enable a service, without starting it. It will start automatically at the next system restart, or it can be started manually, or as a dependency of another service.

systemctl enable —now SERVICE-NAME

Enable a service and start it immediately.

systemctl disable SERVICE-NAME

Disable a service. If it is running, it will continue to run until it is stopped manually. It will not start at the next system restart, but can be started manually, or as a dependency of another service.

systemctl disable —now SERVICE-NAME

Disable a service and stop it immediately.

systemctl re-enable SERVICE-NAME

Stop and restart a service, and restore its default start behavior.

systemctl mask SERVICE-NAME

Mask the service so that it cannot be started by any means. It must be stopped manually, or it will continue to run, possibly in an inconsistent state. The mask command does not take the —now option.

systemctl unmask SERVICE-NAME

Unmask the service. It will start after a system restart, or start it manually. The unmask command does not take the —now option.

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How to use systemctl to manage Linux services

Suppose you’re making configuration changes to a Linux server. Perhaps you just fired up Vim and made edits to the /etc/ssh/sshd_config file, and it’s time to test your new settings. Now what?

Services such as SSH pull their settings from configuration files during the startup process. To let the service know about changes to the file, you need to restart the service so that it rereads the file. You can use the systemctl command to manage services and control when they start.

Restart a service

After editing the /etc/ssh/sshd_config file, use the systemctl restart command to make the service pick up the new settings:

$ sudo systemctl restart sshd

You can verify the service is running by using the status subcommand:

$ sudo systemctl status sshd

Stop and start a service

Perhaps while troubleshooting you need to stop a service to determine whether it is the culprit or interfering with some other process. Use the stop subcommand for this:

Once you determine if this service is associated with the issue, you can restart it:

$ sudo systemctl start sshd

Training & certification

While the restart subcommand is useful for refreshing a service’s configuration, the stop and start features give you more granular control.

Control whether the service starts with the system

One consideration with using stop and start is that the two commands apply only to the current runtime. The next time you boot the system, the service will either start or not start, depending on its default settings. You can use the enable and disable subcommands to manage those defaults.

When you disable the service, it doesn’t start the next time the system boots. You might use this setting as part of your security hardening process or for troubleshooting:

$ sudo systemctl disable sshd

Reboot the system with reboot sudo systemctl reboot , and the service won’t automatically start.

You may determine that you need the service to start automatically. In that case, use the enable subcommand:

$ sudo systemctl enable sshd

The enable subcommand doesn’t start a service, it only marks it to start automatically at boot. To enable and start a service at the same time, use the —now option:

$ sudo systemctl enable --now sshd

Mask a service

You can manually start a disabled service with the systemctl start command after the system boots. To prevent this, use the mask subcommand. Masking the service links its configuration to /dev/null . A user or process will not be able to start this service at all (whereas with a disabled service, a user or process can still start it). Use the unmask subcommand to reverse the setting:

Display all subcommands

Bash’s built-in tab-completion feature is one of my favorite tricks for systemctl (and other commands). When working with commands that support subcommands, this feature saves you a lot of time. Simply type systemctl and add a space, then tap the Tab key twice. Bash displays all available subcommands.

The challenge

Do you think you’re ready to use systemctl to manage your services? Fire up a lab virtual machine and choose a service to work with. Don’t do this on a production system! Make sure you can accomplish the following tasks:

Automation advice

Wrap up

Many management tasks involve the systemctl command, but the ones covered above represent the majority of them. Service management is critical, especially when editing configuration files and hardening a system. Plan to be confident, competent, and quick at using systemctl and its common subcommands.

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