From Newsgroup: alt.os.linux.mint

Hmmm. I was interested in disabling lightdm at system boot time, to
re-enable if/when needed.

So I did 'systemctl | grep lightdm' which showed lightdm apparently
under systemd control. Then 'systemctl disable lightdm' and reboot -
fine, it's disabled; what I wanted.

'systemctl start lightdm' does indeed start it up, and the login greeter screen appears. Exactly the behaviour I want in the longer term.

However, 'systemctl enable lightdm' just gives an error message:

=====

sudo systemctl enable lightdm

Synchronizing state of lightdm.service with SysV service script with /usr/lib/systemd/systemd-sysv-install.
Executing: /usr/lib/systemd/systemd-sysv-install enable lightdm
The unit files have no installation config (WantedBy=, RequiredBy=,
UpheldBy=,
Also=, or Alias= settings in the [Install] section, and DefaultInstance= for template units). This means they are not meant to be enabled or disabled
using systemctl.

Possible reasons for having these kinds of units are:
rCo A unit may be statically enabled by being symlinked from another unit's
.wants/, .requires/, or .upholds/ directory.
rCo A unit's purpose may be to act as a helper for some other unit which has
a requirement dependency on it.
rCo A unit may be started when needed via activation (socket, path, timer,
D-Bus, udev, scripted systemctl call, ...).
rCo In case of template units, the unit is meant to be enabled with some
instance name specified.
=====


none of which is actually terribly illuminating.


So what's up -- how come lightdm seems only partly under systemd control?

And how do I get it back to start at boot time?!

Thanks.
--
Mike Scott
Harlow, England

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From Newsgroup: alt.os.linux.mint

On 09/09/2025 11:05, Mike Scott wrote:

Hmmm. I was interested in disabling lightdm at system boot time, to re- enable if/when needed.

So I did 'systemctl | grep lightdm' which showed lightdm apparently
under systemd control. Then 'systemctl disable lightdm' and reboot -
fine, it's disabled; what I wanted.

'systemctl start lightdm' does indeed start it up, and the login greeter screen appears. Exactly the behaviour I want in the longer term.

However, 'systemctl enable lightdm' just gives an error message:

(etc)

Sorry for following up my own query. It seems you're not supposed to do
this, but rather
systemctl set-default multi-user.target
(or graphical.target, as needed).

(I restored from a backup, and haven't tried the above yet)

But the question is still there: why does systemctl disable something it
can't then re-enable? A strange design choice.
--
Mike Scott
Harlow, England
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From Newsgroup: alt.os.linux.mint

On Tue, 9 Sep 2025 11:58:53 +0100, Mike Scott wrote:

But the question is still there: why does systemctl disable something it can't then re-enable? A strange design choice.

All I can say is, I had login problems with Wayland on my laptop (running Debian Unstable) with lightdm, that went away when I switched to sddm. The login screen looked nicer, too.
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