Questions[ntp](ubuntu)

I am running Ubuntu on an ARM based embedded system that lacks a battery backed RTC. The wake-up time is somewhere during 1970. Thus, I use the NTP service to update the time to the current time.

I added the following line to /etc/rc.local file:

sudo ntpdate -s time.nist.gov

However, after startup, it still takes a couple of minutes until the time is updated, during which period I cannot work effectively with tar and make.

How can I force a clock update at any given time?

UPDATE 1: The following (thanks to Eric and Stephan) works fine from command line, but fails to update the clock when put in /etc/rc.local:

$ date ; sudo service ntp stop ; sudo ntpdate -s time.nist.gov ; sudo service ntp start ; date
Thu Jan  1 00:00:58 UTC 1970
 * Stopping NTP server ntpd     [ OK ] 
 * Starting NTP server          [ OK ] 
Thu Feb 14 18:52:21 UTC 2013

What am I doing wrong?

UPDATE 2: I tried following the few suggestions that came in response to the 1st update, but nothing seems to actually do the job as required. Here's what I tried:

1. Replace the server to us.pool.ntp.org
2. Use explicit paths to the programs
3. Remove the ntp service altogether and leave just sudo ntpdate ... in rc.local
4. Remove the sudo from the above command in rc.local

Using the above, the machine still starts at 1970. However, when doing this from command line once logged in (via ssh), the clock gets updated as soon as I invoke ntpdate.

Last thing I did was to remove that from rc.local and place a call to ntpdate in my .bashrc file. This does update the clock as expected, and I get the true current time once the command prompt is available.

However, this means that if the machine is turned on and no user is logged in, then the time never gets updates. I can, of course, reinstall the ntp service so at least the clock is updated within a few minutes from startup, but then we're back at square 1.

So, is there a reason why placing the ntpdate command in rc.local does not perform the required task, while doing so in .bashrc works fine?

Ubuntu's clock is off by about a half hour:

Where do I even start troubleshooting this?

It's allegedly being set "automatically from the Internet". How can I verify that "the Internet" knows what time it is?

Details

Ubuntu has had plenty of time to communicate with the Internet:

$ date; uptime
Fri May 18 05:56:00 PDT 2012
 05:56:00 up 12 days, 10:48,  2 users,  load average: 0.61, 0.96, 1.15

This time server I found via a web search does appear to know the correct time:

$ date; ntpdate -q north-america.pool.ntp.org
Fri May 18 05:56:09 PDT 2012
server 208.38.65.37, stratum 2, offset 1752.625337, delay 0.10558
server 46.166.138.172, stratum 2, offset 1752.648597, delay 0.10629
server 205.189.158.228, stratum 3, offset 1752.672466, delay 0.11829
18 May 05:56:18 ntpdate[29752]: step time server 208.38.65.37 offset 1752.625337 sec

There aren't any reported errors related to NTP:

$ grep -ic ntp /var/log/syslog
0

After rebooting, the time was automatically corrected and the following appeared in /var/log/syslog:

May 18 17:58:12 aux ntpdate[1891]: step time server 91.189.94.4 offset 1838.497277 sec

A log of the offset reported by ntpdate reveals that the clock is drifting by about 9 seconds every hour:

$ while true; do ntpdate-debian -q | tail -n 1 >> 'drift.log'; sleep 16m; done
^C
$ r -e '
    attach(read.table("drift.log", header=FALSE))
    clock <- as.POSIXct(paste(V1, V2, V3), format="%d %b %H:%M:%S")
    fit <- lm(V10~clock)
    png("drift.png")
    plot(clock, V10, xlab="Clock time", ylab="Time server offset (s)")
    abline(fit)
    mtext(sprintf("Drift rate: %.2f s/hr", fit$coefficients[[2]]*3600))
'

I'm setting up Ubuntu on an embedded machine that runs over a cellular connection, where we pay per byte. The machine also has no RTC battery, so it starts from a random time every boot.

I'd like to ensure that the time gets synced up when the cellular connection comes available so that log messages, etc have real times, but I also don't want to pay an arm and a leg for NTP traffic.

Can I customize the rate at which NTP updates the time? I'm using openntpd currently, but I'm not wedded to it.

The internet is not necessarily up at boot, so ntupdate and related at startup won't work. And scheduling via cron means waiting for the scheduled task to kick in, whereas I want a time daemon to get a time sync ASAP.

I installed NTP server on Ubuntu Server 10.04 using:

sudo apt-get install ntp

The NTP daemon seems working and listening on the 123 port.

However, I was not able to get the time from another machine:

sudo ntpdate -u my_ntp_server
23 Nov 18:48:41 ntpdate[2990]: no server suitable for synchronization found

Is there any necessary configurations to do?

I would like Ubuntu to automatically synchronize my system clock with a timeserver at startup.

However, my PC isn't connected to the Internet until after I've logged in (plus 5 - 10 seconds for good measure).

How can I set it to do this?