Re: [chrony-users] PPS time

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On Tue, Jul 16, 2019 at 10:33:52PM -0700, Bill Unruh wrote:
> On Wed, 17 Jul 2019, Steve Summit wrote:
> > This works quite well, the only drawback being that in practice
> > the name "/dev/pps0" may not be as stable as it needs to be given
> > that it's to be baked into /etc/chrony/chrony.conf as a constant.
> When the pps? is opened, it must use some name is that is not already open. If
> you rerun the serial pps module, if pps0 is in use, then it it cannot be used.
> So you might want to make sure that it is closed before trying to reopen it.
> (How to do that I am not sure, so will not give any comments on that).

Yes, everything that had /dev/pps0 opened needs to be stopped before
the PPS device is attached again. In this case it's probably chronyd
what's keeping the device open.

If using systemd, it may help to bind the chronyd service to the
service which attaches the PPS device. Or, a single service can do
both using a command like this:

ExecStart=/bin/sh -c 'ldattach 18 /dev/ttyS0; exec /usr/sbin/chronyd -n'

When the service is restarted, it should kill both processes and
release the device before starting again.

Miroslav Lichvar

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