Originally Posted by marko
chrony is a bit better at dealing with sporadic network connections. ntp has a maximum error limit of 1000 secs, if the RTC was off more than that, ntpd gives up and exit.
The ntp protocol is quite complex, but yes if the ntp derived time (after sync'ing with multiple (3 min) servers) duesn't match the system time
(aka kernel time) within 1000 seconds, then ntp refuses to set the HWclock (which is not the system clock). So the 1000 second error from system time requires manual intervetion but this prevents setting the hwclock with a grossly bad time without human intervention - that's very reasonably behavior.
It does not just quit or exit. For any amount of error between ntp time and system time - then ntp slowly drifts to clock toward the correct value. ntp also keeps statisticis about the variability of it's own time estimates based on ntp server data and estimates of packet delay - then then it ceases to tweak the system time very much when the system time matches 'within the noise'.
DO NOT do that
Originally Posted by marko
Maybe you make sure you've got the ntpdate.service activated via systemctl and then go in /etc/sysconfig/ntpdate and set SYNC_HWCLOCK to yes like this (quoting the file ):
if you use chrony. the documentation makes clear that chrony leaves a setting and drift file behind and it uses that at boot to correct system time from the hwclock value. detail here ...
Also note that in F16 that chrony is setup to set the hwclock every 11 minutes by default.
See the rtcsync parameter
In /etc/chrony.conf we have
# Enable kernel RTC synchronization.
The documentation is ....
The `rtcsync' directive will enable a kernel mode where the system time
is copied to the real time clock (RTC) every 11 minutes.
This directive is supported only on Linux and cannot be used when the
normal RTC tracking is enabled, i.e. when the `rtcfile' directive is
Originally Posted by yaxattax
I've got Fedora 16 on a laptop - I've read that Linux purposefully doesn't set the RTC because of some dualbooting setups.
That's not quite true. Sometime ther is an option to NOT set the HWclock (usually outsude of chrony/ntp) , but the default a have generally been to set it. F16 does not reset the rtc(hwclock) in scripts but does set it from chrony.
The problem is that because of this, when I am not connected to the network (I enabled network time syncing during setup), during summer time the clock is incorrect. How do I enable the setting of the RTC by linux in order that I do not have this issue?
Why only summer ? Is the error close to 1 hour - as in failure to set daylight saving time ?
i suggest you post the output of .....
[root@lycoperdon stevea]# date ; date -u; TZ=0 hwclock
Wed Apr 11 23:26:53 EDT 2012
Thu Apr 12 03:26:53 UTC 2012
Thu 12 Apr 2012 03:26:54 AM -0.219197 seconds
Then verify the local time and UTC times are correct. Compare to ....
Well chronyd was not updating the RTC, only the system time, so whenever I booted up without a network connection, I saw the time as if summer time had not been applied.
That sort of one-hour error has to do with an incorrect Time-zone setting (and maybe a correcsponding RTC setting error) and not a problem with chrony or system time.
The time zone value is in /etc/adjtime and you should only edit that file using the clock utility on the top panel clock - click it, select edit .. and find some place in your TZ.