I have a running pod and I want to change one of it's container's environment variable and made it work immediately. Can I achieve that? If I can, how to do that?
If you are using Helm 3> according to the documentation:
Automatically Roll Deployments
Often times ConfigMaps or Secrets are injected as configuration files in containers or there are other external dependencies changes that require rolling pods. Depending on the application a restart may be required should those be updated with a subsequent helm upgrade, but if the deployment spec itself didn't change the application keeps running with the old configuration resulting in an inconsistent deployment.
The sha256sum function can be used to ensure a deployment's annotation section is updated if another file changes:
kind: Deployment spec: template: metadata: annotations: checksum/config: {{ include (print $.Template.BasePath "/configmap.yaml") . | sha256sum }} [...]In the event you always want to roll your deployment, you can use a similar annotation step as above, instead replacing with a random string so it always changes and causes the deployment to roll:
kind: Deployment spec: template: metadata: annotations: rollme: {{ randAlphaNum 5 | quote }} [...]Both of these methods allow your Deployment to leverage the built in update strategy logic to avoid taking downtime.
NOTE: In the past we recommended using the --recreate-pods flag as another option. This flag has been marked as deprecated in Helm 3 in favor of the more declarative method above.
Kubernetes is designed in such a way that any changes to the pod should be redeployed through the config. If you go messing with pods that have already been deployed you can end up with weird clusters that are hard to debug.
If you really want to you can run additional commands in your running pod using kubectl exec, but this is only recommended for debug purposes.
kubectl exec -it <pod_name> export VARIABLENAME=<thing>Simply put and in kube terms, you can not.
Environment for linux process is established on process startup, and there are certainly no kube tools that can achieve such goal. For example, if change to your Deployment (I assume you use it to create pods) will roll underlying pods.
Now, that said, there is a really hacky solution reported under Is there a way to change another process's environment variables? that involves using GDB
Also, remember that even if you could do that, there is still application logic that would need to watch for such changes instead of, as it usually is now, just evaluate configuration from envs during startup.
I'm not aware of any way to do it and I can't think of real world scenario where this makes too much sense.
Usually you have to restart a process for it to notice the changed environment variables and the easiest way to do that is restart the pod.
The solution closest to what seem to want is to create a deployment and then use kubectl edit (kubectl edit deploy/name) to modify it's environment variables. A new pod is started and the old one is terminated after you save.