Can someone clarify for me difference between "enable" and "activate" for systemd unit. There are told, if unit has [Install] section than enable should be called, otherwise just activate is enough.

How this handled in startup process? Systemd automagically makes right decision?

  • Systemd/systemctl does not have an activate command, do you mean start? – Wieland Aug 9 '16 at 10:54
  • Yeap, start - for activate. – Constantine Aug 9 '16 at 11:01

To start (activate) a service , you will run the command systemctl start my_service.service, this will start the service immediately in the current session.

To enable a service at boot , you will run systemctl enable my_service.service .

Enable one or more units or unit instances. This will create a set of symlinks, as encoded in the "[Install]" sections of the indicated unit files. After the symlinks have been created, the system manager configuration is reloaded (in a way equivalent to daemon-reload), in order to ensure the changes are taken into account immediately

The /usr/lib/systemd/system/ contains init scripts , when you type systemctl enable to start a service at boot it will be linked to /etc/systemd/system/.

#systemctl enable my_service.service
ln -s '/usr/lib/systemd/system/my_service.service' '/etc/systemd/system/multi-user.target.wants/my_service.service'
  • 1
    under "init scripts" you mean unit files ? – Constantine Aug 9 '16 at 16:52

systemctl enable configures the system to start the service at next reboot (with caveats around correct target states, etc).

systemctl start starts (activates) the service immediately.

So if you want a service to start now and on every reboot then you need to both enable and start the service.

  • 3
    The last sentence is not true: systemctl enable --now will both start and enable a unit. – Wieland Aug 9 '16 at 12:07

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