[systemd-devel] Requires and After

[James Feeney]

On 1/2/19 12:50 AM, Olaf van der Spek wrote:
> Activation by itself guarantees basically nothing.

"Activation" guarantees activation.  Activating, for instance, a service unit is quite a bit more significant than "nothing".

>> Because, as far as I know, "Requisite=" is completely broken in systemd.

> How is it broken?

In the case of a service unit Requisite upon the existence of a device unit, systemd  will completely ignore the dependency and merrily start the service unit anyway, which, in this case, uselessly attempts to operate upon a nonexistent device.  Of course, the service unit will fail, outright, or after time-out, wasting compute resources, and producing lots of otherwise avoidable error messages.

I have not really tested Requisite= with other unit type interactions, but then, I also don't know of anyone actually using Requisite= with any other use case.  As far as I know, Requisite= is effectively a "no op".

In the past, systemd developers have not been especially motivated to fix Requisite=, though without actually declaring "Won't Fix" - more of a "Never Used It Myself, Don't Really Care".