Trying to optimize RAM usage on a 32MB device, I noticed, that ntp is permanently resident in RAM. Any suggestions how to replace it, i.e. using cron to do single-shot time syncs periodically ?
-n option to prevent ntpd becoming a daemon also
-q option looks interesting.
# ntpd -h ntpd: unrecognized option: h BusyBox v1.28.4 () multi-call binary. Usage: ntpd [-dnqNwl -I IFACE] [-S PROG] [-p PEER]... NTP client/server -d Verbose (may be repeated) -n Do not daemonize -q Quit after clock is set -N Run at high priority -w Do not set time (only query peers), implies -n -S PROG Run PROG after stepping time, stratum change, and every 11 mins -p PEER Obtain time from PEER (may be repeated) -l Also run as server on port 123 -I IFACE Bind server to IFACE, implies -l
Depending on how accurate you need your notion of time, 802.11 requires 25 ppm accuracy for 2.4 GHz and 20 ppm accuracy for 5 GHz.
25 ppm over an hour, for reference, is 90 ms per hour, or a little over 2 seconds a day. (This assumes the kernel clock is based off the same crystal as used for the radios' frequency sysnthesis.)