busybox/examples/var_service/ntpd/ntp.script

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#!/bin/sh
# Note that there is no provision to prevent several copies of the script
# to be run in quick succession. In fact, it happens rather often
# if initial syncronization results in a step.
# You will see "step" and then "stratum" script runs, sometimes
# as close as only 0.002 seconds apart.
#
# Script should be ready to deal with this.
dt=`date '+%Y-%m-%d %H:%M:%S'`
echo "`tail -n 199 -- "$0.log" 2>/dev/null`" >"$0.log.$$"
if test x"$1" = x"unsync" \
; then
# No replies for our NTP requests were seen for some time.
#
# Among more mundate cases like network outages, this happens
# if we ran for a LONG time (days) and ntp server's IP has changed.
# ntpd has no code to re-resolve peers' addresses to IPs,
# we need to help it:
#
echo "$dt: $1"\
"syncronization lost, restarting ntpd"\
>>"$0.log.$$"
mv -- "$0.log.$$" "$0.log"
kill $PPID
exit
fi
if test x"$stratum" != x"" \
&& test x"$poll_interval" != x"" \
&& test 4 -ge "$stratum" \
&& test 128 -le "$poll_interval" \
; then
echo "$dt: $1"\
"freq_drift_ppm=$freq_drift_ppm"\
"offset=$offset"\
"stratum=$stratum"\
"poll_interval=$poll_interval,"\
"setting hardware clock"\
>>"$0.log.$$"
mv -- "$0.log.$$" "$0.log"
exec hwclock --systohc
fi
echo "$dt: $1"\
"freq_drift_ppm=$freq_drift_ppm"\
"offset=$offset"\
"stratum=$stratum"\
"poll_interval=$poll_interval"\
>>"$0.log.$$"
mv -- "$0.log.$$" "$0.log"