Can someone clarify for me difference between "enable" and "start" for a systemd unit. I have been told that if a unit has an [Install] section, then enable should be called, otherwise just start is enough.
How this handled in startup process? Systemd automagically makes right decision?
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'
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.
systemctl enable --now will both start and enable a unit.
– Wieland
Aug 09 '16 at 12:07
systemctl --help. It's in the manpage, but buried in a paragraph, which is not usually how subcommand options are listed in manpages. I always struggle to locate this option as I don't need it often and never seem to remember if it's a systemctl start or systemctl enable option. :-/
– bobpaul
Apr 12 '20 at 19:06
activatecommand, do you meanstart? – Wieland Aug 09 '16 at 10:54