Marking a refclock unusable / changing its precision at runtime

Is there a way to modify the selection priority of a refclock at
runtime? I am working with a PPS source that doesn't have any way to
suppress its ticks when the reference source becomes unavailable (eg
GPS signal lost), but I am able to monitor the state of the reference.
I'm looking for a way to 'inform' chrony that this source is no longer
suitable to trust after a holdover period, and avoid the several ms of
drift that would otherwise be allowed before the source is marked
falseticker.

I would prefer not to run my monitoring task as root, so that it can
restart chrony (and thus also lose all of chrony's state with its
servers), so I was looking for a way to remove / noselect / unprefer'
the refclock via chronyc, but these options all seem to only be
available for NTP servers. Is there something I am missing, or is the
only option to modify the configuration file and restart chrony
entirely (or implement a SOCK/SHM shim)?

Keenan

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