Base Debian package selection installs ntp about ansible-role-base

[mika]

I just reviewed #11, thanks for working on that!

Regarding:

Or: we could try to detect the most common ntp packages (i.e. ntp, chrony + systemd-timesyncd), keep the one installed and only else install the given one.

I think it makes sense to use a global default, and for the systems that are supposed to ship something else, we should adjust the configuration accordingly. But too much dynamic behavior might not be worth the trouble, at least yet? :)

[jkirk]

What about setting a variable base_ntp_client to let us choose which ntp package should be installed? Just created the PR #11. Please have look. Thx!

[jkirk]

Or: we could try to detect the most common ntp packages (i.e. ntp, chrony + systemd-timesyncd), keep the one installed and only else install the given one.

[jkirk]

Thx for the review! Full ACK on "too much dynamic behavior might not be worth the trouble, at least yet? :)" 😉

Just another note (to self): As this is (currently) not supported by this role, we should document how to use non-default / local time servers.

For systemd-timesyncd it is /etc/systemd/timesyncd.conf:

[Time]
NTP=ntp1.example.com ntp2.example.com ntp3.example.com ntp4.example.com

For ntp it is /etc/ntp.conf:

pool time.example.com iburst

or

server time.example.com iburst

We use iburst by default. I think it is still ok. From ntp.conf(5):

iburst: When the server is unreachable, send a burst of six packets instead of the usual one. The packet spacing is normally 2 s; [...]

We should use server instead of pool if no round-robin DNS is involved, though.

[jkirk]

After some digging I think we should favor chrony over ntp (from Choosing Between NTP Daemons):

Chrony should be preferred for all systems except for the systems that are managed or monitored by tools that do not support chrony, or the systems that have a hardware reference clock which cannot be used with chrony.

The list in Differences Between ntpd and chronyd is too long to quote.

[jkirk]

Another good Comparison of NTP implementations.