How to Enable or Disable Services in Ubuntu Systemd

Often, there is a need to enable or disable services temporarily or permanently on our Ubuntu system. Sometimes, we may require certain services to start up automatically on boot up e.g ssh or web servers and sometimes we may need to disable services we no longer require and are hogging the CPU and RAM.

In this guide, we take a look at how we can enable and disable services on Ubuntu. To do this, we must first understand that there are 3 main init systems for Ubuntu

• Systemd
• Upstart
• SysV

Each init system has a different way of starting and stopping services. We'll take a look at each one of these.

How to enable and disable services in  Systemd init

To start a service in systemd run the command as shown:

systemctl start service-name

For example, to start apache web service, run

systemctl start apache2

To verify that the service is running, run

systemctl status apache2

Output
● apache2.service - LSB: Apache2 web server
   Loaded: loaded (/etc/init.d/apache2; bad; vendor preset: enabled)
  Drop-In: /lib/systemd/system/apache2.service.d
           └─apache2-systemd.conf
   Active: active (running) since Thu 2018-03-15 17:09:05 UTC; 35s ago
     Docs: man:systemd-sysv-generator(8)
   CGroup: /system.slice/apache2.service
           ├─2499 /usr/sbin/apache2 -k start
           ├─2502 /usr/sbin/apache2 -k start
           └─2503 /usr/sbin/apache2 -k start

Mar 15 17:09:04 ip-172-31-41-251 systemd[1]: Starting LSB: Apache2 web server...
Mar 15 17:09:04 ip-172-31-41-251 apache2[2475]:  * Starting Apache httpd web ser
Mar 15 17:09:05 ip-172-31-41-251 apache2[2475]:  *
Mar 15 17:09:05 ip-172-31-41-251 systemd[1]: Started LSB: Apache2 web server.

To stop the service running service

systemctl stop apache2

To confirm that the service is not running, run

systemctl status apache2

Output
● apache2.service - LSB: Apache2 web server
   Loaded: loaded (/etc/init.d/apache2; bad; vendor preset: enabled)
  Drop-In: /lib/systemd/system/apache2.service.d
           └─apache2-systemd.conf
   Active: inactive (dead) since Thu 2018-03-15 17:19:47 UTC; 12s ago
     Docs: man:systemd-sysv-generator(8)
  Process: 2822 ExecStop=/etc/init.d/apache2 stop (code=exited, status=0/SUCCESS
  Process: 2687 ExecStart=/etc/init.d/apache2 start (code=exited, status=0/SUCCE

Mar 15 17:10:11 ip-172-31-41-251 systemd[1]: Starting LSB: Apache2 web server...
Mar 15 17:10:11 ip-172-31-41-251 apache2[2687]:  * Starting Apache httpd web ser
Mar 15 17:10:12 ip-172-31-41-251 apache2[2687]:  *
Mar 15 17:10:12 ip-172-31-41-251 systemd[1]: Started LSB: Apache2 web server.
Mar 15 17:19:46 ip-172-31-41-251 systemd[1]: Stopping LSB: Apache2 web server...
Mar 15 17:19:46 ip-172-31-41-251 apache2[2822]:  * Stopping Apache httpd web ser
Mar 15 17:19:47 ip-172-31-41-251 apache2[2822]:  *
Mar 15 17:19:47 ip-172-31-41-251 systemd[1]: Stopped LSB: Apache2 web server.

To enable apache2 service on boot up run

systemctl enable apache2

To disable apache2 service on boot up run

systemctl disable apache2

To restart the service

systemctl restart apache2

To check whether the service is currently configured to start on the next boot up

systemctl is-enabled apache2

Output
Executing /lib/systemd/systemd-sysv-install is-enabled apache2
enabled

To check whether the service is active

systemctl is-active apache2

Output:

active

How to remove Systemd services completely

What if you installed a package, and later on decide that you don't need it anymore. How do you go about removing it completely? Follow the commands below.

First, stop the service

systemctl stop service-name

Then disable the service

systemctl disable service-name

Removing the service in systemd

rm /etc/systemd/system/service-name

rm /etc/systemd/system/service-name/[related symlinks]

Reload systemd

systemctl daemon-reload

Finally run,

systemctl reset-failed

How to enable and disable services in Upstart init

Upstart init system was unveiled just before systemd It was used in Ubuntu 9.10 to Ubuntu 14.10. It was later phased out paving way for systemd init in Ubuntu 15.04 and newer versions. In this example, let's see how we can start and stop, enable and disable services in Ubuntu 14.04.

Upstart makes use of config files for controlling services. These files are held under the /etc/init directory. These files are made up of plain text sections organized in stanzas and each stanza describes a service and how it works.

To check whether a service is running or not run the command below

initctl status service-name

OR

service service-name status

OR

status service-name

In this example, we'll check the status of cups, a Linux print server.

 initctl status cups

OR

service cups status

OR

status cups

Output:

cups start/running, process 3029

To stop the service run the command below

initctl stop cups

OR

service cups stop

OR

stop cups

Output

cups stop/waiting

To enable a service in Upstart init

In /etc/init/*.conf file, you'll find the "respawn" directive which jump-starts a service should it crash unexpectedly or should the system reboot. Its normally enabled by default.

For example , in /etc/init/cups.conf file below,

The first argument (3)  is the number of attempts it will try to restart and the second argument (12) is the time interval between retries. If it fails to restart automictically. it will be kept in a stopped state.

To disable a service in upstart init

Run the command below:

echo manual >> /etc/init/service.override

This creates an override file that disables a service without altering the job definition at all.
For cups service, the command will be

echo manual >> /etc/init/cups.override

Upon a reboot of the system, cups will be in a stopped state. If you wish to re-enable the service, you must delete the  /etc/init/cups.override file.

Sysv-rc-conf tool

This is a text-based console that gives you an overview of different services and runlevels they are scheduled to start. It can be installed using the following command:

apt-get install sysv-rc-conf

To execute the tool, run

sysv-rc-conf

Jobs-Admin tool

This is another feature that allows you to control services and processes in a GUI environment. You can install this by running.

apt-get install jobs-admin

How to enable and disable services in  SysV init

To enable a service in SysV init run

update-rc.d enable service-name

For instance, If you want to enable apache web server, you would run

update-rc.d enable apache2

To disable a service, run

update-rc.d disable service-name

For example:

update-rc.d disable apache2

Conclusion

Nearly all Linux systems run on Systemd init such as Ubuntu, Debian, RHEL, and CentOS Stream. You'll, therefore, discover that you'll be using more of the systemctl command to start, stop, enable and disable services. We welcome you to try out the commands as shown in this guide. Thank you.