Services & Daemons

In Linux, a service is a program that runs in the background and performs a specific function. A daemon is a type of service that also runs in the background and often starts at boot time. These processes can be controlled using the systemctl or service command. Services and daemons are an important part of the Linux operating system, as they provide various functions and services that allow the system to run smoothly. There are many different types of services and daemons that can be found on a typical Linux system, and you can find more information about them in the documentation for your specific distribution.

Useful systemctl commands

Start the specified service.

systemctl start <service>

Stop the specified service.

systemctl stop <service>

Restart the specified service.

systemctl restart <service>

Enable the specified service to start automatically at boot time.

systemctl enable <service>

Disable the specified service from starting automatically at boot time.

systemctl disable <service>

Show the current status and runtime information for the specified service.

systemctl status <service>

Show the dependencies for the specified service.

systemctl list-dependencies <service>

List all installed unit files on the system.

systemctl list-units --all

Display Running Services

The systemctl command with the grep command will display a list of all running services and daemons on your Linux system. The grep command will search the output of systemctl for the string "running" and only display the lines that contain that string.

systemctl | grep running

For more readable output:

systemctl --no-pager | grep running | column -t

Display Enabled Services

systemctl list-unit-files --state=enabled is a command that shows a list of unit files that are currently enabled on the system. The --state option specifies the state of the unit files that you want to see. By using --state=enabled, you will see only unit files that are enabled and will be started automatically when the system boots.

systemctl list-unit-files --state=enabled