I am new to MongoDB devops, and I’m having issues upgrading multiple servers from Ubuntu 16.04 to 18.04. Doing the upgrade breaks the Mongo databases present on the system. The servers are running the Ubuntu official versions of MongoDB, 2.6.10 on 16.04 and 3.6.3 after the upgrade. As far as I understand the way to fix it is to downgrade mongo and to the rolling updates.
This does not feel like the intended way to upgrade the systems, and I have so far been unable to find a propper way to do it. Is it really the intended result to have to downgrade Mongo manually and upgrade step by step?
I appreciate any suggestions, thank you in advance.
Related bug on Launchpad: https://answers.launchpad.net/ubuntu/+source/mongodb/+question/691008