Start kubernetes container with specific command

I spend 45 minutes looking for this. Then I post a question about it and find the solution 9 minutes later.

There is an hint at what I wanted inside the Cassandra example. The command line below the image:

id: cassandra
kind: Pod
apiVersion: v1beta1
desiredState:
  manifest:
    version: v1beta1
    id: cassandra
    containers:
      - name: cassandra
        image: kubernetes/cassandra
        command:
          - /run.sh
        cpu: 1000
        ports:
          - name: cql
            containerPort: 9042
          - name: thrift
            containerPort: 9160
        env:
          - key: MAX_HEAP_SIZE
            value: 512M
          - key: HEAP_NEWSIZE
            value: 100M
labels:
  name: cassandra

Despite finding the solution, it would be nice if there was somewhere obvious in the Kubernetes project where I could see all of the possible options for the various configuration files (pod, service, replication controller).