1) Power outage and RPi starts up afterwards before Internet gateway is ready
2) RPi moved to location with no Internet
3) RPi has an RTC unit installed, does it care at all about Internet time?
4) If the RTC is not that good and deviates from true time, does the RPi reset the RTC to correct time if Internet time is available or will it run exclusively on the RTC?
I am asking because I thought the RPi would start back in 1970 and move to current time only after getting Internet connection, but last night we had a power outage in the office and my RPi started when power returned. This RPi does not have an RTC module installed.
At that time the ISP had no Internet connection for several hours. This particular Pi has a cron job to check for connection to a specific WiFi network so it logs the state every minute and on the logline is a timestamp too.
I can see that when the outage happens the next log line is predated to some time before the outage
Code: Select all
2016-06-04 02:05:01 No connection to WiFi 2016-06-04 02:06:01 No connection to WiFi 2016-06-04 01:18:01 No connection to WiFi <== Back to earlier time (-48 min)! Power loss. 2016-06-04 01:19:01 No connection to WiFi ... 2016-06-04 18:47:01 No connection to WiFi 2016-06-04 18:48:01 No connection to WiFi 2016-06-04 20:25:30 No connection to WiFi <== Another jump, forward by 37m29s 2016-06-04 20:26:01 No connection to WiFi
Then when Internet is restored after some 18 hours it looks like the RPi syncs to correct network time.
This RPi runs a version of Raspbian updated about 6 weeks ago.