Circular dependency between local_unbound and ntpd?

Paul Mather paul at gromit.dlib.vt.edu
Tue Jul 14 14:48:01 UTC 2015


On Jul 14, 2015, at 10:33 AM, krad <kraduk at gmail.com> wrote:
> 
> As
> 
> $ grep REQUIRE /etc/rc.d/ntpd
> # REQUIRE: DAEMON ntpdate FILESYSTEMS devfs
> 
> 
> You could set something similar to the following in the rc.conf
> 
> ntpdate_hosts="a.b.c.d w.x.y.z"
> ntpdate_enable=yes

Thanks for that suggestion.  I assume the "a.b.c.d w.x.y.z" are IP addresses, not hostnames, otherwise we'd have the same problem.

The /etc/rc.d/ntpdate startup script has a "REQUIRE: NETWORKING ..." and /etc/rc.d/local_unbound has a "BEFORE: NETWORKING" in it, meaning it will be running before ntpdate runs.  That means DNS resolution will require an accurate clock and, I assume, mean that ntpdate will require IP addresses, too?

So, it still comes down to this: do I need to know the IP address of an NTP server to be able to use local_unbound safely with NTP?

Cheers,

Paul.


> 
> 
> 
> 
> On 14 July 2015 at 14:43, Paul Mather <paul at gromit.dlib.vt.edu <mailto:paul at gromit.dlib.vt.edu>> wrote:
> I believe I ran afoul of a circular dependency between local_unbound and ntpd on my 10.2-PRERELEASE system.  I use a stock /etc/ntp.conf and use ntpd_sync_on_start="YES".
> 
> Last night, a BIOS settings reset cause my CMOS clock to go WAY out of synch for the first time.  No problem, I thought: NTP will correct it at boot.
> 
> Wrong!
> 
> When my system booted, the time was not corrected.  Also, DNS resolution was not working.  I figured out it was because local_unbound relies on an accurately set clock, but the clock could not be set accurately because my stock ntp.conf requires working DNS resolution to reach the NTP servers.
> 
> That sounds like a potential circular dependency to me.
> 
> My workaround at the time was to look up 0.freebsd.pool.ntp.org <http://0.freebsd.pool.ntp.org/> on another system; stop ntpd; then do a ntpdate using the IP addresses to set the clock. Once the clock was set accurately, things were all hunky dory.
> 
> Does anyone have any suggestion for an automatic way around this?  I guess one way would be to put the IP address of an NTP server into my ntp.conf file, so at least one would be reachable without needing a working DNS?
> 
> My main concern is for those systems like my Raspberry Pi and Beaglebone Black that don't have a battery-backed clock.  I currently don't use local_unbound on those, but it seems like I'd encounter this problem routinely if I did.
> 
> Cheers,
> 
> Paul.
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