Document that timedatectl set-ntp == systemctl {enable/disable} systemd-timesyncd.service

[wlcrls47]

I'm confused by the documentation, on whether timedatectl set-ntp ONLY enables or disables systemd-timesyncd.service, or if it does this AND other things. Are they interchangeable? I'm betting they aren't interchangeable, because the other systemd services don't have a non-systemctl way to be enabled/disabled (as far as I've ran into.)

Asking, because "timedatectl set-ntp true" fails from the boot cd in arch-chroot with "Failed to create bus connection: No such file or directory". But, systemctl runs without needing a bus connection.

[falconindy]

systemctl runs without a bus connection because it has fallback logic to enable/disable units in the absence of a usable bus connection. timedatectl defers work to timedated by communicating with it over the bus. So, it makes sense that systemctl works and timedatectl fails in the absence of a system bus. This situation ought to improve once kdbus is around.

Looking at the code, calling timedatectl set-ntp true is equivalent to calling systemctl --now enable systemd-timedated. Similarly, timedatectl set-ntp false is equivalent to calling systemctl --now disable systemd-timedated.

[poettering]

It only controls systemd-timesyncd.service.

Today the setting is pretty redundant since "systemctl enable systemd-timesyncd.service" is also hooked up to PolicyKit, and thus clients such as GNOME could just invoke that directly.

[poettering]

We should probably update the man page to explain in more detail what this does.

[poettering]

We should still document this. Reopening hence.

[richardmaw-codethink]

http://www.freedesktop.org/software/systemd/man/timedatectl.html#set-ntp%20%5BBOOL%5D seems clear to me that it's about enabling/disabling the service.