NTP problems for newbies

Patrick Ernst patrick at aroaustralia.com
Fri Oct 8 11:42:49 CST 2004

The more linux savvy may well be aware of this but for the less 
experienced, like me :) ...

NTP (ntpd) has a problem with servers with intermittent connections to 
the internet, typically dial up, adsl or cable.  After starting the ntpd 
daemon, you will see in your logs that it is nicely syncing time, then 
after a period of time, perhaps days as in my case, you could get errors 
like the following in your log (syslog by default).

8 Oct 18:58:14 ntpd[10589]: sendto( Invalid argument
 8 Oct 19:15:17 ntpd[10589]: sendto( Invalid argument
 8 Oct 19:32:21 ntpd[10589]: sendto( Invalid argument
 8 Oct 19:49:24 ntpd[10589]: sendto( Invalid argument
 8 Oct 20:06:30 ntpd[10589]: sendto( Invalid argument
 8 Oct 20:23:34 ntpd[10589]: sendto( Invalid argument

The problem is identified on ntp.org

>ntpd binds a socket to each specific IP address assigned to all of the
>interfaces. If the IP address is dynamic and changes, the socket to which
>the old address was bound becomes invalid and furthermore won't know about
>the new IP address since it does not rescan for interfaces after it starts
>up. BIND does do this at a admin-settable interval so it doesn't matter.
>I do have designs to implement this in NTP but it will be a while before
>I get to implement this.
A workaround is to uninstall ntp and install chrony. This app is 
designed to handle intermittent connections.



PS: why do I want accurate time? Well I don't want to miss the bus, do I? :)

Patrick Ernst
ARO Australia Pty Ltd
Ph: 0404 883 145
eMail: patrick at aroaustralia.com
iNet: www.aroaustralia.com 

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