Ryan Malloy
6881489bf6
What the Raspberry Pi time-server guides get wrong on a Pi 4, with the measurements. The headline artifact is a four-line pps-gpio patch: PREEMPT_RT force-threads IRQ handlers, and pps-gpio takes its timestamp inside its handler, so the realtime kernel puts a scheduler between the electrical edge and the clock. IRQF_NO_THREAD takes RMS offset from 2468 ns to 199 ns. - kernel/ the patch - dashboard/ live status page (position hidden by default) - docs-site/ the write-up (Astro/Starlight, brass, no tutorial section)
5 lines
289 B
Plaintext
5 lines
289 B
Plaintext
# Least-privilege: the dashboard user may run ONLY this one read-only command.
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# `chronyc -c clients` is privileged (returns "501 Not authorised" otherwise),
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# and this is the served-client list the dashboard displays. Nothing else.
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gpsntp ALL=(root) NOPASSWD: /usr/bin/chronyc -c clients
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