How to bring sanity into user-mode systemd usage.


First:

Create /etc/systemd/system/user@.service.d/00env.conf, i.e. a
"drop-in" (more like merge-in; can override and amend stuff) for
user@.service (which is in /lib/systemd so it shouldn't be edited),
with the contents:

[Service]
ExecStart=
ExecStart=/bin/sh -l -c 'systemd --user'

That means override the ExecStart field (first needs to be cleared
with the line setting it to empty) to wrap the systemd call in 'sh -l'
to make it read my ~/.profile and so get my desired environment in
systemd and all processes it launches.


Second:

Now my user systemd instance has the SYSTEMD_UNIT_PATH env var from my
~/.profile and successfully loads stuff from ~/etc/systemd instead of
the stupid default path, and in that directory I have:

1. my service files, each also using /bin/sh to launch the process
because ExecStart is stupid and expects absolute executable paths
instead of traversing $PATH, and

2. default.target.d/init.conf where I list all said services as
dependencies of this default.target (a pseudo-service that's started
up by default so you can trigger other stuff from there).


Done!