Systemd is now used by default in most Linux distributions, from Fedora and Red Hat to Ubuntu, Debian, openSUSE, and Arch. The systemctl command allows you to get information about systemd’s status and control running services.
Despite the controversy, this at least introduces some standardization across Linux distributions. The same commands will allow you to manage services in the same way on any Linux distribution using systemd.
Note: To modify your system configuration on Linux distribution like Ubuntu that uses sudo, you’ll need to prefix the commands here with sudo. On other Linux distributions, you’ll need to become the root user with the su command first.
Check If Your Linux System Is Using Systemd
If you’re not sure whether your Linux distribution is using systemd, open a Terminal window and run the following command. This shows you the version number of systemd on your Linux system, if it does have systemd installed:
systemd –version
Analyze the Boot Process
The systemd-analyze command allows you to view information about your boot process, such as how long it took and which services (and other processes) added the most time to the boot process.
To view information about the startup process in general, run this command:
systemd-analyze
To view how long each process took to start, run this command:
systemd-analyze blame
View Units
Systemd uses “units,” which can be services (.service), mount points (.mount), devices (.device), or sockets (.socket). The same systemctl command manages all these types of units.
To view all available unit files on your system:
systemctl list-unit-files
To list all running units:
systemctl list-units
To list all failed units:
systemctl –failed
Manage Services
To view a list of enabled and disabled services, you use the same systemctl command as above, but tell it to only list services:
systemctl list-unit-files –type=service
The systemctl command allows you to start, stop, or restart a service. You can also tell a service to “reload” its configuration.
The status command is the only action here that will print and output to the terminal. The other commands will silently take effect.
systemctl start name.servicesystemctl stop name.servicesystemctl restart name.servicesystemctl reload name.servicesystemctl status name.service
Use the systemctl enable command to have systemd automatically start a service (or other type of unit) at bootup. The systemctl disable command disables a services and stops it from starting automatically with your computer.
systemctl enable name.servicesystemctl disable name.service
You can “mask” a service or other unit to prevent it from starting up at all. You’ll need to unmask it before it can start in the future:
systemctl mask name.servicesystemctl unmask name.service
There’s a lot more to systemd and its various commands than this, of course. Systemd offers a variety or power-management commands to shut down, reboot, hibernate, and otherwise control the system’s power state. You can write your own unit files to create services and mount points or edit the existing unit files.
Systemd also offers “targets,” which are similar to runlevels, but different. instead of a number, targets have names — it’s possible for systemd to be in multiple target states at once. Systemd also offers its own system journal, which can be accessed with the journalctl command. By default, it stores system logs in binary format — but you can switch to plain-text format logs, if you prefer.
The Arch Linux wiki has more in-depth information on systemd, and most of the information there applies to systemd on all Linux distributions. You should also check your your own Linux distribution’s systemd documentation for more information.
Image Credit: Bert Heymans on Flickr
information credit: how to geek
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