There is a container in my Kubernetes cluster which I want to debug.
But there is nonetstat, no ip and no apk.
Is there a way to upgrade this image, so that the common tools are installed?
In this case it is the nginx container image in a K8s 1.23 cluster.
Alpine is a stripped-down version of the image to reduce the footprint. So the absence of those tools is expected. Although since Kubernetes 1.23, you can use the kubectl debug command to attach a debug pod to the subject pod.
Syntax:
kubectl debug -it <POD_TO_DEBUG> --image=ubuntu --target=<CONTAINER_TO_DEBUG> --share-processes
Example:
In the below example, the ubuntu container is attached to the Nginx-alpine pod, requiring debugging. Also, note that the ps -eaf output shows nginx process running and the cat /etc/os-release shows ubuntu running. The indicating process is shared/visible between the two containers.
ps@kube-master:~$ kubectl debug -it nginx --image=ubuntu --target=nginx --share-processes
Targeting container "nginx". If you don't see processes from this container, the container runtime doesn't support this feature.
Defaulting debug container name to debugger-2pgtt.
If you don't see a command prompt, try pressing enter.
root@nginx:/# ps -eaf
UID PID PPID C STIME TTY TIME CMD
root 1 0 0 19:50 ? 00:00:00 nginx: master process nginx -g daemon off;
101 33 1 0 19:50 ? 00:00:00 nginx: worker process
101 34 1 0 19:50 ? 00:00:00 nginx: worker process
101 35 1 0 19:50 ? 00:00:00 nginx: worker process
101 36 1 0 19:50 ? 00:00:00 nginx: worker process
root 248 0 1 20:00 pts/0 00:00:00 bash
root 258 248 0 20:00 pts/0 00:00:00 ps -eaf
root@nginx:/#
Debugging as ubuntu as seen here, this arm us with all sort of tools:
root@nginx:/# cat /etc/os-release
NAME="Ubuntu"
VERSION="20.04.3 LTS (Focal Fossa)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 20.04.3 LTS"
VERSION_ID="20.04"
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
VERSION_CODENAME=focal
UBUNTU_CODENAME=focal
root@nginx:/#
In case ephemeral containers need to be enabled in your cluster, then you can enable it via feature gates as described here.