Please document MTU settings

[smnbbrv]

Hi there,

thank you for a great plugin!

Today I spent several hours with a quite specific issue which I still cannot fully understand. Probably it is about some specific config of the network we use for our cluster.

Actors:

• Kubernetes
• Drone CI & Drone Docker (this) plugin
• Alpine image

Actually, what happens is exactly repeating this alpine issue: when I run apk update as one of the dockerfile's run command it freezes.

So, decreasing the MTU (I set 1000) solved the issue, however I need to go to the source code to find out there is a setting like that:

kind: pipeline
type: kubernetes
name: default

steps:
  - name: dockerize
    image: plugins/docker
    settings:
      ...
      mtu: 1000

Would be super if the setting gets documented. Thank you!

[tboerger]

I'm not sure about the documentation for that, there is no advanced configuration section within the plugin index, and the majority of users don't have to care about these options at all.

[BigeYoung]

Hello, dear developer.

In fact, many people are bothered by this problem:
https://discourse.drone.io/t/drone-on-kubernetes-with-docker-plugin-strange-network-problem/8420/5
https://discourse.drone.io/t/solved-issue-kubernetes-runner-cert-validation-issues-with-plugin-docker/7712/2
https://liejuntao001.medium.com/fix-docker-in-docker-network-issue-in-kubernetes-cc18c229d9e5

It seems that running docker in docker in Kubernetes is not so smooth.

So if we can document the MTU settings, it will be able to help many people save a lot of time!

[schaze]

After over a year of intermittent issues with docker-in-docker builds on drone in kubernetes this finally helped. Please add a line of documentation for this. It will help A LOT of people!

[rule88]

This indeed should be part of documentation, especially as the resulting behavior is hard to debug from a developer point of view. In fact, the whole setup (kubernetes + drone) should result in an environment in which developers don't have infrastructure as a concern.

Documenting this setting with some reference to/over MTU sizes (and the effect if not set properly) would hopefully prevent others needing to make some deep dives in networking.