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I have two computers connected with an Ethernet cable. The first computer, let's call it the "master" is also connected to the Internet via a wireless network. It's running ntp and getting its time from 0.ubuntu.pool.ntp.org, etc. The second computer, let's call it the "slave" is only connected to the master and is running chrony. I want the slave to track the master for time syncing purposes.

I have set up link-local IPv6 addresses on the master: inet6 fe80::1/128 scope link and the slave: inet6 fe80::2/128 scope link The two computers can ping each other and ssh into each other using these IPv6 addresses. So far so good.

I'm not sure how to configure /etc/ntp.conf on the master and /etc/chrony/chrony.conf on the slave in order to get the slave to track the master.

In the IPv4 case, it seems like what I had to do is these modifications:

# /etc/ntp.conf (master)
restrict 169.254.0.0 mask 255.255.0.0
broadcast 169.254.255.255

# /etc/chrony/chrony.conf (slave)
server 169.254.1.1 minpoll -1 maxpoll 2 prefer

This seems to work (although I have my doubts about its correctness) assuming I've also set the corresponding link-local IPv4 addresses. What's the IPv6 equivalent of this configuration?

PS. avahi is also running on both computers, which may be complicating things.

Spyros Maniatopoulos
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  • chrony doesn't support link-local addresses, so you would need to configure the two computers with unique local addresses (from block fd00::/8), which can be specified in the configuration file. – mlichvar Oct 04 '17 at 17:08
  • Thanks for the reply @mlichvar ! Does `ntp` support *link-local* IPv6 ? I might be able to use `ntp` on both computers (instead of `ntp` on one and `chrony` on the other) – Spyros Maniatopoulos Oct 04 '17 at 17:23
  • Yes, ntp should work correctly with IPv6 link-local addresses since version 4.2.8. – mlichvar Oct 04 '17 at 20:26
  • @mlichvar Cool, thanks! I'm currently running `ntp 4.2.6`, but upgrading shouldn't be a significant problem. Btw, if you wanna summarize your two comments in an answer, I will gladly accept and upvote it. – Spyros Maniatopoulos Oct 04 '17 at 22:56

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