Troubleshooting OpenShift

Question 1

Display the list of nodes in a cluster

Answer 1

oc get nodes

Question 2

Displays the current CPU and memory usage of each node

Answer 2

oc adm top nodes

Question 3

Displays the resources used by a node

Answer 3

oc describe node my-node-name

Question 4

Show the cluster version

Answer 4

oc get clusterversion

Question 5

Show elaborated details about the cluster status

Answer 5

oc describe clusterversion

Question 6

List all cluster operators

Answer 6

oc get clusteroperators

Question 7

View crio logs on a given node

Answer 7

oc adm node-logs -u crio my-node-name

Question 8

View kubelet logs on a given node

Answer 8

oc adm node-logs -u kubelet my-node-name

Question 9

View all journal logs on a given node

Answer 9

oc adm node-logs my-node-name

Question 10

Login into a node and check if kubelete is running

Answer 10

oc debug node/my-node-name
chroot /host
systemctl is-active kubelet

Question 11

Login into a node and show low-level information about all local containers running on the node

Answer 11

oc debug node/my-node-name
chroot /host
crictl ps

Question 12

Display a pod logs

Answer 12

oc logs my-pod-name

Question 13

Display a container logs

Answer 13

oc logs my-pod-name -c my-container-name

Question 14

Run a given deployment as root

Answer 14

oc debug deployment/my-deployment-name –as-root

Question 15

Change a pod log level to shows max amount of information

Answer 15

oc get pods –loglevel 10

Question 16

Extract your oc login token so you can use it in a curl request

Answer 16

oc whoami -t

Question 17

Opens a shell inside a pod to run shell commands

Answer 17

oc rsh my-pod-name

Question 18

Copies local files to a location inside a pod

Answer 18

oc cp /local/path my-pod-name:/container/path

Question 19

Creates a TCP tunnel from local-port on your workstation to local-port on the pod

Answer 19

oc port-forward my-pod-name local-port:remote-port

Question 20

List storage classes of a cluster

Answer 20

oc get storageclass

Question 21

Add a volume to an application

Answer 21

oc set volumes deployment/example-application –add
–name example-pv-storage
–type pvc
–mount-path /var/lib/example-app
–claim-class nfs-storage
–claim-mode rwo
–claim-size 15Gi
–claim-name example-pv-claim

Question 22

Delete a volume

Answer 22

oc delete pvc/example-pvc-storage

Question 23

List cluster nodes using admin cert as opposed to login/password

Answer 23

oc –kubeconfig /home/user/auth/kubeconfig get nodes

Question 24

Delete kubeadmin user

Answer 24

oc delete secret kubeadmin -n kube-system

Question 25

List all pods inside internal image registry project

Answer 25

oc get pod -n openshift-image-registry

Question 26

Tail the logs of the internal image reg operator

Answer 26

1) Determine the pod name with: oc get pod -n openshift-image-registry
2) oc logs -f OPERATOR-POD-NAME -n openshift-image-registry

Question 27

Verify that etc is running

Answer 27

1) oc debug node/master01
2) chroot /host
3) crictl ps –name etcd

Question 28

Check if an image exist on image registry

Answer 28

skopeo inspect docker://registry.redhat.io/rhel8/postgresql-13:1

Question 29

App was created with typo in image reg. How to fix it?

Answer 29

1) Find the right image. Use skopeo to inspect
2) oc edit deployment/deployment-name

Question 30

When you create a storage volume, you need to provide a parameter claim-class. How do you obtain values for this parameter?

Answer 30

oc get storageclasses

Question 31

Content to add to Oauth.yaml when adding htpasswd identify provider

Answer 31

Question 32

Steps to add a htpasswd provider

Answer 32

1) Create htpasswd file and populate it
2) Create secret with htpasswd file
3) Assign admin users the cluster-admin role
4) Extract oauth
5) Add identity provider to oauth.yaml
6) Replace oauth.yaml

Question 33

Check what happened to a failed app

Answer 33

1) oc get pods
2) oc get status
3) oc get events
4) skopeo inspect docker://registry.redhat.io/rhel8/postgresq-13:1
5) oc edit deployment/psql

Question 34

Different volum access modes

Answer 34

rwx: vol can be mounted as read-write by many nodes.
rwo: vol can be mounted as read-write by a single node
rox: vol can be mounted as read-only by many nodes