dhcpcd-discuss

On 14/01/2020 10:42, nighthawk wrote:
> The other day I updated my Debian (Armbian) system to Buster and
> noticed afterwards, that my NTP Daemon was restarting every 15
> seconds.
>
> Took me a long time to figure out why. It's dhcpcd's hook scripts,
> because my router is offering IPv6 resolvers via DHCPv6 name_servers
> option with a ridiculously short lifetime of 60 seconds. This results
> in the following message:
>
> Jan 13 21:00:39 armbian dhcpcd[9066]: eth0: renew in 15, rebind in 22,
> expire in 60 seconds
>
> Since I don't actually need the nameserver information, I tried to
> "set nooption dhcp6_name_servers". To my understanding this should
> cause dhcpcd to ignore the entire DHCPv6 option, but it is still using
> the 60 seconds lifetime value (because it's the shortest timeframe or
> the last option in the DHCP packet?). I didn't check if the rest of
> the option is processed, because the resolv.conf hook is disabled
> (since a long time).
>
> I then tried "reject dhcp6_name_servers" , but this blocks the entire
> packet, which also contains the IP addresses for my system - those I
> want.
>
> I am running "dhcpcd 7.1.0". I know it's not the latest version. Would
> updating (probably) fix my issue? In that case I'll look into building
> a more recent version. Or does anyone have other ideas what I could
> try? Maybe an undocumented minimum lifetime override setting?
>
> Changing my router or ISP is unfortunately not an option.

I don't see how DNS will restart NTP.
However, that dhcpcd version does request NTP by default, but it should only 
restart NTP if the configuration has changed.

Newer versions do not request NTP.
Try commenting out "option ntp_servers" in /etc/dhcpcd.conf

Roy