You are debugging a program which is running in a container.
The program usually connects to some remote tcp port (e.g. for it's output, telemetry, logging...).
For faster debugging, you want to make it connect to a service which is running locally on your workstation.
Usually, you can do this with ssh remote port forwaring. But you're on k8s and you don't have access to the container directly with ssh.
Currently (2024), kubectl can do local port forwarding (like ssh -L), but it does not support remote port forwarding (like ssh -R).
If you can install sshd in the container, you can do remote port forwarding.
For instance, if the container is running a debian linux:
- Access to the container with
kubectl exec -ti -n $namespace $pod -- bash
Run these commands in the container:
apt-get install -y openssh-server vim
mkdir /root/.ssh
echo $your_ssh_public_key >> /root/.ssh/authorized_keys
/usr/sbin/sshd -D
Run these commands locally:
kubectl port-forward -n $namespace $pod 2222:22 &
ssh root@localhost -p2222 -R8080:localhost:8080 -Nf
Test the connection in the container:
curl http://localhost:8080