systemd: how to enable a service automatically from the first boot?

Question

I am using systemd to handle some tasks and I have a service file which works fine once enabled with systemctl.

Now, I would like to enable it automatically from the first boot.

I know that putting a replacement file into /etc/systemd/system/ replaces the behavior of the file with the same name into /lib/systemd/system/.

There is a way to enable a service file automatically just to putting it in some directory ?

Answer 1

IMPORTANT NOTE: The following works for me under Ubuntu. It should work as is under Debian. RPM based distros prevent the auto-start by default, but it may still get you closer to your goal.

In most cases, you want to install it in the multi-user.target using the install section as follow:

[Install]
WantedBy=multi-user.target

This means the your-package.postinst script will automatically start the daemon for you.

Note that if you have your own your-package.postinst script, you have to make sure to include the Debian helper as in:

#!/bin/sh

#DEBHELPER#

...your own script here...

Without the #DEBHELPER# pattern, the packager will not add the default code and as a result your daemon won't get enabled and started automatically. The code added there will enable and start the service:

systemctl enable <service-name>
systemctl start <service-name>

unless the service is static (does not have an [Install] section as shown above.) A static service requires a special command line to be enabled and that's not available by default:

systemctl add-wants multi-user.target <service-name>

As we can see, the command includes multi-user.target which the default #DEBHELPER# (systemd, really) has no clue about unless you have an [Install] section.

The package must also be built with the systemd extension. This means having the following in your debian/rules file:

%:
    dh $@ --with systemd --parallel

That should get you set.

Answer 2

sudo systemctl enable <service-name> will enable service at boot time.

http://www.dynacont.net/documentation/linux/Useful_SystemD_commands/ has a list of useful commands. And there's always man systemctl and man systemd.

Answer 3

You could use systems.preset for default enabled units.

Systems.preset allows to configure set of units to be enabled/disabled

vendor preset in systemctl status unit refers to this.

For more info how use this refer linked man page