wantedBy not working when used from upstream systemd units

[worldofpeace]

Describe the bug
I've noticed on several occasions, and again with a PR #81087 which has a unit

# tlp - systemd startup/shutdown service
#
# Copyright (c) 2020 Thomas Koch <linrunner at gmx.net> and others.
# This software is licensed under the GPL v2 or later.

[Unit]
Description=TLP system startup/shutdown
After=multi-user.target NetworkManager.service
Before=shutdown.target
Documentation=https://linrunner.de/tlp

[Service]
Type=oneshot
RemainAfterExit=yes
ExecStart=/nix/store/42m41jbsvbc7qh25k42cdc5jf2yjsf87-tlp-1.3.1/sbin/tlp init start
ExecStop=/nix/store/42m41jbsvbc7qh25k42cdc5jf2yjsf87-tlp-1.3.1/sbin/tlp init stop

[Install]
WantedBy=multi-user.target

The wantedBy didn't do anything when it was included with systemd.packages.

We had to add it manually like:

systemd.services.tlp.wantedBy =  [ "multi-user.target" ];

Looking at nixpkgs, it seems like others have noticed this.

[worldofpeace]

Similarly, we had to do wants manually in gnome-settings-daemon

nixpkgs/nixos/modules/services/desktops/gnome3/gnome-settings-daemon.nix

Line 50 in 954d44f

systemd.user.targets."gnome-session-initialized".wants = [

. But everything has the links in the package.

[lheckemann]

I'm guessing that the [Install] section, which is put into effect by systemctl enable which in turn creates symlinks in /etc/systemd/system/multi-user.target.wants (for instance), is not currently respected by systemd.packages. EDIT: i.e. we need to use or emulate the behaviour of systemctl enable

[stale]

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[worldofpeace]

this is still really important

[stale]

I marked this as stale due to inactivity. → More info

[aanderse]

Still relevant.

[nixos-discourse]

This issue has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/disable-a-systemd-service-while-having-it-in-nixoss-conf/12732/3

[ElvishJerricco]

Can't we just run systemctl enable --root=where/ever * or something?

[aanderse]

@ElvishJerricco can you elaborate on the --root=where/ever part?

[ElvishJerricco]

@aanderse When building the generateUnits derivation, we could do something along the lines of for x in ${units}; do systemctl enable --root=$out $x; done. The --root arg makes it operate on a different root tree and not on any running daemon, so all it will do is create necessary symlinks and implement the [Install] section.