k3s support

[smerschjohann]

Describe the problem/challenge you have
Currently k3s as kubernetes cluster is not supported as it deploys containerd at a different location and not all settings are exposed to override it at creation time.

Description of the solution you'd like
Either detect a k3s instance and deploy the buildkit pod/deployment with the correct settings or allow the customization in such a way that it will work on k3s.

A working deployment looks like this:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: buildkit
[...]
        volumeMounts:
        - mountPath: /etc/buildkit/
          name: buildkitd-config
        - mountPath: /run/containerd/containerd.sock
          name: containerd-sock
        - mountPath: /var/lib/buildkit/buildkit
          mountPropagation: Bidirectional
          name: var-lib-buildkit
        - mountPath: /var/lib/containerd
          mountPropagation: Bidirectional
          name: var-lib-containerd
        - mountPath: /run/containerd
          mountPropagation: Bidirectional
          name: run-containerd
        - mountPath: /var/log
          mountPropagation: Bidirectional
          name: var-log
        - mountPath: /tmp
          mountPropagation: Bidirectional
          name: tmp
        - mountPath: /var/lib/rancher
          mountPropagation: Bidirectional
          name: rancher
[..]
      volumes:
      - configMap:
          defaultMode: 420
          name: buildkit
        name: buildkitd-config
      - hostPath:
          path: /run/k3s/containerd/containerd.sock
          type: Socket
        name: containerd-sock
      - hostPath:
          path: /var/lib/buildkit/buildkit
          type: DirectoryOrCreate
        name: var-lib-buildkit
      - hostPath:
          path: /var/lib/rancher/k3s/agent/containerd
          type: Directory
        name: var-lib-containerd
      - hostPath:
          path: /run/containerd
          type: Directory
        name: run-containerd
      - hostPath:
          path: /var/log
          type: Directory
        name: var-log
      - hostPath:
          path: /tmp
          type: Directory
        name: tmp
      - hostPath:
          path: /var/lib/rancher
          type: Directory
        name: rancher

This means:

• an additional hostPath mount must be added (/var/lib/rancher),
• the var-lib-containerd must be set to: /var/lib/rancher/k3s/agent/containerd
• the containerd-sock must be set to: /run/k3s/containerd/containerd.sock

Design/Architecture Details
It would be enough to change the following:

• enable the customization of the var-lib-containerd path in addition to the containerd-sock.
• allow adding additional volumes / volumeMounts

Environment Details:

k3s v1.21.5+k3s2

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[sacesare]

k0s too)

[spkane]

k3s does not appear to be the core problem here.

colima uses k3s and this can be made to work there without adjusting code. (see: #133)

So, I think the issue may be more specific to the specific implementation that is being used.

That being said, making this tool configurable would be a big win and something that will make it much more useable in general.

[Blackmamba23]

Would be nice if k3s is supported, getting the following error for k3s cluster

FailedMount MountVolume.SetUp failed for volume "containerd-sock" : hostPath type check failed: /run/containerd/containerd.sock is not a socket file

[sdemura]

./buildkitd --containerd-worker-addr /run/k3s/containerd/containerd.sock

[zcrisler]

Just encountered this issue on an RKE2 v1.24.9+rke2r2 cluster. The suggested changes to the buildkit Deployment worked.

Perhaps it would be simpler to work around these types of issues if kubectl buildkit create had a --dry-run option that output the Deployment and ConfigMap resources instead of creating them?