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ntpd: explain why scripts can be run in quick succession

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Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko
2010-01-25 19:30:16 +01:00
parent 3581c62515
commit 24928ffd8d
2 changed files with 24 additions and 9 deletions
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20
examples/var_service/ntpd/ntp.script
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@ -1,10 +1,12 @@
#!/bin/sh
exec 2>/dev/null
echo "`tail -n 99 "$0.log"`" >"$0.log"
exec >>"$0.log"
exec 2>&1
# Note that there is no provision to prevent several copies of the script
# to be run in quick succession. In fact, it happens rather often
# if initial syncronization results in a step.
# You will see "step" and then "stratum" script runs, sometimes
# as close as only 0.002 seconds apart.
#
# Script should be ready to deal with this.
dt=`date '+%Y-%m-%d %H:%M:%S'`
@ -13,17 +15,23 @@ if test x"$stratum" != x"" \
&& test 4 -ge "$stratum" \
&& test 128 -le "$poll_interval" \
; then
echo "`tail -n 199 -- "$0.log" 2>/dev/null`" >"$0.log.$$"
echo "$dt: $1"\
"freq_drift_ppm=$freq_drift_ppm"\
"offset=$offset"\
"stratum=$stratum"\
"poll_interval=$poll_interval,"\
"setting hardware clock"
"setting hardware clock"\
>>"$0.log.$$"
mv -- "$0.log.$$" "$0.log"
exec hwclock --systohc
fi
echo "`tail -n 199 -- "$0.log" 2>/dev/null`" >"$0.log.$$"
echo "$dt: $1"\
"freq_drift_ppm=$freq_drift_ppm"\
"offset=$offset"\
"stratum=$stratum"\
"poll_interval=$poll_interval"\
>>"$0.log.$$"
mv -- "$0.log.$$" "$0.log"