Support for systemd-timesyncd

[eliasp]

Support for systemd-timesyncd should be implemented for client-only setups where NTP server functionality isn't required:

• Check, whether the latest available systemd version is >=216 [*]
• Ensure, the latest (>=216) version is installed
• Disable other implementation/services providing NTP client functionality
• Enable systemd-timesyncd (timedatectl set-ntp 1) [**]

[*] The reason for wanting >=216 is, that since this release the whole NTP handling in systemd was streamlined. Before that, individual NTP services could provide drop-in configs which would then be used by systemd. This was quite a mess and error-prone. See also this entry from the NEWS file:

CHANGES WITH 216:

        * timedated no longer reads NTP implementation unit names from
          /usr/lib/systemd/ntp-units.d/*.list. Alternative NTP
          implementations should add a

            Conflicts=systemd-timesyncd.service

          to their unit files to take over and replace systemd's NTP
          default functionality.

[**] Once https://github.com/saltstack/salt/issues/20392 is implemented, the whole timedatectl setup should be done via DBus which provides a proper interface for this instead of fiddling with cmd.run output/results.

[aboe76]

@eliasp shouldn't that be in a different formula?

[eliasp]

As it serves the same purpose as any other NTP client (and might even replace existing NTP setups on many clients in the near future) I felt like the ntp-formula would be the best place to handle this to just abstract "timekeeping" without relying on a specific implementation of it.

[aboe76]

I can understand, but I prefer a clean relationship between formula name and what it does. Timesyncd is a different beast

[aboe76]

see systemd-formula