How to source an sh file in a pod to create env variables?

Question

I have a pod with multiple init containers and one main container. One of the init container create a sh file with some export commands like:

export Foo=Bar

I want to source the file so it creates the env variable like this:

 containers:
    - name: test
      command:
        - "bash"
        - "-c"
      args:
        - "source /path/to/file"

It doesn't create the env variable. But if I run the source command directly in the container it works. What is the best way to do this using the command option in the pod definition?

Answer 1

If you are looking for create the sh in the init container with the variables and then use in the "main container" here is a quick example:

manifest

apiVersion: v1
kind: Pod
metadata:
  name: mypod
  labels:
    name: mypod
spec:
  initContainers:
  - name: my-init-container
    image: alpine:latest
    command: ["sh", "-c", "echo export Foo=bar > /shared/script.sh && chmod +x /shared/script.sh"]
    volumeMounts:
      - name: shared
        mountPath: /shared
  containers:
  - name: mycontainer
    image: mycustomimage
    resources:
      limits:
        memory: "32Mi"
        cpu: "100m"
    volumeMounts:
      - name: shared
        mountPath: /shared
  volumes:
    - name: shared

Dockerfile

FROM alpine:latest

COPY entrypoint.sh .

ENTRYPOINT ["./entrypoint.sh"]
CMD ...

entrypoint.sh

#!/bin/sh
. /shared/script.sh
env
exec "$@"

logs

$ kubectl logs pod/mypod
<...>
Foo=bar
<...>

As you can see we can created a script file in the init container with Foo=bar variable and source the file in the "main container", the script is there the volume shared mounted in both containers.

Most of the situations we use configMaps/secrets/vaults and inject that as variables in the containers as the others answers mentioned. I recommend checking if those can solve your problem first.