Re: NTP.conf pool vs server
- Date: Wed, 7 Jun 2017 15:54:26 +0100
- From: Darac Marjal <mailinglist@xxxxxxxxxxxx>
- Subject: Re: NTP.conf pool vs server
On Wed, Jun 07, 2017 at 10:35:23AM -0400, Gene Heskett wrote:
On Wednesday 07 June 2017 08:56:59 ray wrote:I would like to know the correct syntax for entering a server entry for stretch. All the documentation I find says to list the ntp servers in the file as: server 0.XX.pool.ntp.org server 1.XX.pool.ntp.org An example source from 2017 is https://wiki.debian.org/DateTime When I open /etc/ntp.conf on my new stretch installation, I find this format: pool 0.debian.pool.ntp.org iburst pool 1.debian.pool.ntp.org iburst The latest Debian doc says to start the line with 'server'. The latest Debian implementation starts the line with 'pool'. Are these interchangeable?
As I understand it "server" will do name resolution once and pick an IP from the result. "pool" will periodically refresh the name and cycle to a different member of the pool.
Additionally, there is a parameter 'iburst' which I did not find in the Debian docs but found at http://doc.ntp.org/4.1.1/confopt.htm
Did you install ntp-doc? Did you check there?
Thanks, RayBegin rant: From someone who is currently battling a fresh jessie install that didn't even come with ntpdate installed, and which using the above format in /etc/ntp.conf is still about 12 hours off on an rpi-3. Installing ntpdate and attempting to start it gets me a no servers found message, yet they are defined as discussed above, and the network is fully accessible to all other forms of communication. That doc on www.ntp.org is nice, but worthless to someone who just wants it to work. I have quite a zoo of machines here, and I see little advantage to each one banging on a network server, when it needs an update. But does it give even a hint of how to make this machine, or heaven forbid, my router, which keeps time via ntp, and which I believe has the time broadcast enabled, (its dd-wrt in a buffalo box) into a server that the rest of my machines can listen to to get the correct time. If I could achieve that, it would reduce the loading on the time servers at debian or pool.ntp.org by a factor of 5 or 6 just from my home network.
By a factor of 5 or 6? You think you own 5 or 6 times more servers than everyone else combined? (I think you just mean "reduce [...] by 5 or 6"). Does your router inform other devices on the network that it should be used as a time server? In the DHCP specification there is an option called "time-servers". The idea is that a network administrator sets this to be the approved time servers for the network and clients synchronise to that. In debian, this is facilitated by /etc/dchp/dhclient-exit-hooks.d/ntp (at least, if you use the ISC DHCP client). That script will read the "time-servers" option from the DHCP packet, write /var/lib/ntp/ntp.conf.dhcp and ensure that file is included from your main ntp.conf. As far as I'm aware, this is default behaviour.
But a manpage that actually tells us how to do that must be sick bird, because its not been written yet. Man page writers please get real, and tell us how to do something like getting our home networks all synchronized to our routers which can then broadcast it to the rest of our network.
There's an XY problem here. You probably shouldn't put this information into the NTP man pages, as it's not NTP that's doing the work. The information about the "time-servers" option *is* in the DHCP manpage, but probably there's no information about the specific hook being included. If the NTP hook is Debian-specific, then... I don't know where that should be documented. If it's upstream, then... Well, if every project documented every decision for creating every file, then there'd be a lot to wade through.
Such a scheme can easily keep us on time with any errors within a few milliseconds, more than adequate enough for the girls I go with. While reducing the load on the servers by at least 80%. So how about a manpage that tells us how to do that? If its not illegal according to some rfc that is. Rant off. Thanks for reading. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene>
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