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By default, any container that we launch will run as root. Most of the processes we launch don't really require, for example, to be able to install packages on the container. We can reduce it's privileges by setting the SecurityContext at the Pod level or at the container level.
Let's say we want to run a pod using the UID 1001 and the GID 1002. In the following YAML definition we are setting the securityContext at the pod leve, so all the containers will run as user's UID 1001 and GID 1002:
apiVersion: v1 kind: Pod metadata: name: setUID spec: securityContext: runAsUser: 1001 runAsGroup: 1002 containers: - image: busybox:latest name: setUID args: - sleep - "24h"
Once we deploy this pod:
$ kubectl apply -f pod-context.yml
It will keep running for 24h: We can run a command on it to get the UID and GID using kubectl exec to check it is working as expected:
$ kubectl exec setUID -- id uid=1001 gid=1002
We could also set the securityContext at the container level, so each container within the Pod can ran using a different UID:
apiVersion: v1 kind: Pod metadata: name: setUID spec: containers: - image: busybox:latest securityContext: runAsUser: 1001 runAsGroup: 1002 name: setUID1001 args: - sleep - "24h" - image: busybox:latest securityContext: runAsUser: 9999 runAsGroup: 9999 name: setUID9999 args: - sleep - "24h"
Posted on 19/02/2021