[Rancher] What does Rancher support for Docker on Ubuntu cover?

Note:

Only upstream Docker has been validated and certified for Rancher Support. Ubuntu's own distribution of Docker is not covered by the Rancher support matrix.

Rancher support in this scenario will start with issue troubleshooting and RCA (root cause analysis). Where the root cause has been identified as an issue with Docker on Ubuntu, Rancher will do one of the following, to help Customer resolve the issue:

• Should the issue have been resolved in a later version of Docker, Rancher will recommend Customer to upgrade to this version, along with the necessary upgrades to versions of Ubuntu and Rancher that has been certified for this later version of Docker.
• If no fix is available yet for the issue, however, the situation is critical that an urgent solution is needed, Rancher shall fork Docker with a fix, as possible. Further, Rancher will submit a PR for the fix to Docker for consideration to be accepted into upstream. However, there is no guarantee that the PR will be accepted and merged into upstream Docker.
• If a code fix is not possible, Rancher will advise Customer to contact Canonical directly for issue resolution. Should a new version or patch be provided by Canonical, Rancher will validate its relevant product versions on the new version or patch and certify it as supported for Customer deployment.