Change MTU for Bitbucket Pipelines Docker Daemon

[János Mikó]

I'm running the Bitbucket Pipelines Runner in our Rancher based Kubernetes cluster. It registers well, and I am able to run basic Pipelines and everything is going fine until some steps of the Pipeline has to download a large file. (In our case it was npm install)

I tried to search everywhere and I found a possible issue with network MTU.

The MTU size on the server is 1500, but the Kubernetes Network Provider is using 1450. I tried to update DIND to use the following settings:

- name: docker-in-docker
  image: docker:20.10.7-dind
  args:
    - "--mtu=1300"

Now if I attach to the Bitbucket Runner container (atlassian/bitbucket-pipelines-runner), I can see the following setting in `docker network inspect bridge`:

./docker network inspect bridge | grep mtu
"com.docker.network.driver.mtu": "1300"

 Sadly if I attach from here to a pipeline container (or the atlassian/bitbucket-pipelines-docker-daemon container) I will still see the original:

docker network inspect bridge | grep mtu
"com.docker.network.driver.mtu": "1500"

Is it possible somehow to change the MTU for the bitbucket pipelines docker daemon?

Regards,

Janos

[Alex Martin]

Hey, had same issue as you. Found this guide helpful. https://janosmiko.com/blog/2021-09-08-bitbucket-pipelines-runners-in-k8s/