Lab3.4 step16, pod pending

I hope it's ok that I append my problem here as my initial problem is exactly the same.

student@master:~$ kubectl get deployments,pod
NAME                    READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/nginx   0/1     1            0           29m
 
NAME                        READY   STATUS              RESTARTS   AGE
pod/nginx-f89759699-mbt5v   0/1     ContainerCreating   0          29m

This is an overview about all my pods:

student@master:~$ kubectl get pods --all-namespaces
NAMESPACE     NAME                                       READY   STATUS              RESTARTS   AGE
default       nginx-f89759699-kgvkc                      0/1     ContainerCreating   0          4m37s
kube-system   calico-kube-controllers-7dbc97f587-w4pkt   1/1     Running             1          13h
kube-system   calico-node-5ts9j                          0/1     Completed           1          3h7m
kube-system   calico-node-hj89f                          0/1     Running             1          13h
kube-system   coredns-66bff467f8-j6xtn                   1/1     Running             1          14h
kube-system   coredns-66bff467f8-lk65s                   1/1     Running             1          14h
kube-system   etcd-master                                1/1     Running             1          14h
kube-system   kube-apiserver-master                      1/1     Running             1          14h
kube-system   kube-controller-manager-master             1/1     Running             1          14h
kube-system   kube-proxy-qt6bm                           1/1     Running             1          14h
kube-system   kube-proxy-r6f77                           0/1     Error               1          3h7m
kube-system   kube-scheduler-master                      1/1     Running             1          14h

student@master:~$ kubectl get nodes
NAME     STATUS   ROLES    AGE    VERSION
master   Ready    master   15h    v1.18.1
worker   Ready    <none>   4h1m   v1.18.1

When I check for errors of my pod 'nginx-f89759699-mbt5v' I see the following events:
Warning FailedCreatePodSandBox 3m17s (x117 over 28m) kubelet, worker Failed to create pod sandbox: rpc error: code = Unknown desc = failed to create a sandbox for pod "nginx-f89759699-mbt5v": Error response from daemon: cgroup-parent for systemd cgroup should be a valid slice named as "xxx.slice"

I'm not sure what the error message means. Can anyone help me with that?

(I followed the lab guide to set up the Kubernetes cluster. I'm on a GCE environment, running Ubuntu 18.04.)

Ok, it seems that the problem is solved. All pods have READY 1/1 now. Thank you for your help!
I learnt a lesson: just check the events for every faulty pod. It sounds so simple and still I had not yet fully embraced it.

One Calico pod said:

Events:
  Type    Reason          Age                       From             Message
  ----    ------          ----                      ----             -------
  Normal  SandboxChanged  2m35s (x2185 over 7h55m)  kubelet, worker  Pod sandbox changed, it will be killed and re-created.

And that reminded me that I've played around with different start options for the Docker runtime on my worker node. After I changed it to the same settings as my Master node and a restart of the pod (deletion) on the Master node, it was finally working.