Add OS check to ensure host machine uses Ubuntu 18.04+

[mrsimonemms]

IMPORTANT self-hosted installations of Gitpod should target an LTS version of Ubuntu. The non-LTS versions are included in the checks for completeness but are untested.

Gitpod requires that the Kubernetes cluster is hosted on an Ubuntu machine. Make a KOTS preflight check to check this:

OS	Version	Result
Ubuntu	20.04 and above	Pass
Ubuntu	18.04 - 19.10	Warn
Ubuntu	Less than 18.04	Fail
Any non-Ubuntu	Any	Fail

Have attempted this already and this has proven problematic getting the data in the collector. Barry's code in shared docs SHOULD work, but isn't working currently so will require investigation.

See internal comment for details/documentation

[hewjoe]

Hi @mrsimonemms, we are just getting started with on-premise Gitpod running in our EKS environment. Our standard is using Amazon Linux 2 with their EKS optimized AMI. We have it up and running with the latest version and are working on modifications to support in our air gapped VPC config.

I am curious about why you require that the Kubernetes cluster is hosted on Ubuntu? Is there a limitation on other platforms that we are missing here? If so, is there an opportunity to support other platforms in the future?

BTW: I tried looking for more details in the linked internal Slack comments, but didn't have access.

[mrsimonemms]

@hewjoe in order to create a workspace, we need to do various operations on the node itself (check out the initContainers as part of the ws-daemon daemonset). This is only supported on Ubuntu. This is linked to why we can only support Kubernetes clusters with a containerd runtime and a few other restrictions.

It's not inconceivable that we'll support other platforms in future, but it's not currently planned.

Basically, treat this as a requirement as you would any other.

The full list of restrictions is on gitpod.io

[hewjoe]

Thanks for the context. We have seen some issues with runc which we were able to stumble through, but did not have anything we would be comfortable using in prod. Hearing your explanation, I understand it will not be possible to work around these unless we make the switch to Ubuntu.

[mrsimonemms]

The code is going to be something like this:

  collectors:
    - copyFromHost:
        collectorName: os-release
        image: busybox:1
        name: os-release
        hostPath: /usr/lib/os-release
        extractArchive: true
  analyzers:
    - textAnalyze:
        checkName: "Host operating system distribution"
        fileName: os-release/*/os-release
        regexGroups: 'NAME="(?P<Name>\w+)"'
        outcomes:
          - pass:
              when: "Name == Ubuntu"
              message: Host operating system detected as Ubuntu
            fail:
              message: Host operating system not detected as Ubuntu
    - textAnalyze:
        checkName: "Host operating system version"
        fileName: os-release/gitpod-1/os-release
        regexGroups: 'VERSION_ID="(?P<Version>.*)"'
        outcomes:
          - fail:
              when: "Version < 18.04"
              message: Host operating system must be at least Ubuntu 18.04
          - pass:
              when: "Version == 18.04"
          - pass:
              when: "Version == 20.04"
            warn:
              message: Unknown Ubuntu version
`

[mrsimonemms]

This is currently blocked by this issue