On 5/9/2011 1:31 AM, Per Jessen wrote:
Stan Hoeppner wrote:
This is not correct. You're assuming that ntpd doesn't perform sanity checks on the system time when the daemon starts, which is not the case.
The sanity check may be disabled with -g in which case using ntpdate/sntp/ntpd -q at start up becomes pointless.
'ntpdate -q' has always been 'pointless', unless you just want to look at the offset without modifying the clock. I do so on occasion to see how accurately my local ntp server is keeping time. For instance:
/$ ntpdate -q tick.wustl.edu ntp.okstate.edu tick.uh.edu server 128.252.19.1, stratum 1, offset -0.003486, delay 0.09729 server 139.78.135.14, stratum 1, offset 0.003479, delay 0.11545 server 129.7.1.66, stratum 1, offset -0.003950, delay 0.13434 9 May 02:39:55 ntpdate[31040]: adjust time server 128.252.19.1 offset -0.003486 sec
Mt nptd server is Debian Squeeze atop kernel 2.6.34.1, running ntp 4.2.6.p2+dfsg-1+b1. The machine is home grown w/ an 11 year old Abit main board. 0.003 seconds offset, not too shabby. ;) I've seen offset with 4 leading zeros (after the decimal) in the past. I've never seen less than two leading zeros. For most applications on my network, time this accurate is overkill, but it's nice to have.
I acquired 'special' permission many years ago to use a few stratum 1 USNO servers mostly because at that time I lived in a city where one of them is located, and because I only have one client querying infrequently. USNO is the official time keeper for the US Military and the US Government, including ships at sea via GPS. USNO has the most accurate timekeeping devices on the planet--atomic clocks. Most (if not all) of the stratum 2 servers in the US query the USNO stratum 1 servers.
-- Stan