[LinuxPPS] refclock_nmea: cannot find PPS path "/dev/ttyS0" in the system

[Udo van den Heuvel]

2.6.21.1 gives me, after starting ntpd:

May  5 20:24:53 epia ntpd[4949]: Listening on interface #11 ppp0,
82.92.197.115#123 Enabled
May  5 20:24:53 epia ntpd[4949]: kernel time sync status 0040
May  5 20:24:53 epia ntpd[4949]: refclock_nmea: cannot find PPS path
"/dev/ttyS0" in the system
May  5 20:24:53 epia ntpd[4949]: configuration of 127.127.20.0 failed

(even after I try setserial hardpps or ppsctl enable)

What now?