Ubuntu Updates/Reboots - how does it work?

[humptydumpty]

I have three Cloudron servers (1 VPS, 2 Home-Servers). I get the reboot notification on the VPS and one of the homeservers usually the same day, but the other homeserver it could take an extra few days. How does this work? Any way to force or set a specific schedule?

Reboot dates:
VPS: 03/29
HS1: 03/28
HS2: 04/02 (weird!)

P.S. I don't believe it's sub/domain related (alphabetical) since they're all on the same base domain and the server that's usually late starts with "E" subdomain, while the other homeserver start with an "R".

[BrutalBirdie]

Thinking bigger, like 5000 Servers.
If all servers update and reboot at the same time you don't want that.
A certain degree of randomness is welcome in this case.

So I would assume this is intended by Ubuntu it self.

[joseph]

Ubuntu calls this "phasing" - https://documentation.ubuntu.com/sru/en/latest/explanation/standard-processes/#phasing and also https://help.ubuntu.com/community/PhasedUpdates (haven't read all the details myself)

[BrutalBirdie]

@joseph That is how it was called!
I just flew over the unattended-upgrade docs and scratched my hat how it was called again.

[humptydumpty]

I see. Thanks for the clarification guys