• Bug report
• Request for enhancement (RFE)

systemd 232-3

Arch

When it is convenient to have a WantedBy=some-other-unit dependency in addition to a
WantedBy= sys-subsystem-net-devices-%p.device

then it would seem necessary to qualify the Start from some-other-unit with a
Requisite= sys-subsystem-net-devices-%p.device

so that the unit does NOT actually start when no such device actually exists yet.

Instead, the Requisite=...device dependency has no effect whatsoever, and systemd will attempt to start the unit whether the device exists or not.

Additionally, in issue #4256, there is the statement that, "we should also point out in the man page explicitly that Requisite needs to be combined with After= to be useful".

Instead, combining:
Requisite= sys-subsystem-net-devices-%p.device
After= sys-subsystem-net-devices-%p.device

produces "crazy" systemd errors, in the nature of:
systemd[1]: [email protected]: Main process exited, code=killed, status=15/TERM
systemd[1]: Stopped Enslaved enp0s7@bond0.
systemd[1]: [email protected]: Unit entered failed state.
systemd[1]: [email protected]: Failed with result 'signal'.
systemd[1]: Requested transaction contradicts existing jobs: Resource deadlock avoided
systemd[1]: Requested transaction contradicts existing jobs: Resource deadlock avoided
systemd[1]: Requested transaction contradicts existing jobs: Resource deadlock avoided

such that the entire unit start fails. What this "Resource deadlock" might be is a unknown, with a useless "opaque" error message.

It is reasonable to expect that systemd would not "try" to start a unit with a Requisite device dependency when that device does not exist!

And it makes no sense to involve some ordering dependency when Start/Stop dependencies are expected to be "orthogonal" to, and independent of, ordering dependencies!