Handy kubectl commands

Patch container in a running Pod.

# Set parameters
# Pod Name
PNAME=alertmanager-prometheus-k8s-alertmanager-0
# Container Name
CNAME=alertmanager
# Container Image Name
CIMAGE=alertmanager
# Container Image Version
CVER=v0.25.1

# Get current image version (and state)
$ kubectl get pods -n monitoring ${PNAME} -o=jsonpath="{.spec.containers[?(@.name==\"${CNAME}\")].image}{\"|\"}{.status.containerStatuses[?(@.name==\"${CNAME}\")].state}"; echo
---
quay.io/prometheus/alertmanager:v0.24.0|{"running":{"startedAt":"2023-09-08T15:35:47Z"}}

# Patch container with new image version.
$ kubectl -n monitoring patch pod ${PNAME} -p "{\"spec\":{\"containers\":[{\"name\": \"${CNAME}\", \"image\": \"${CIMAGE}:${CVER}\"}]}}"
---
pod/alertmanager-prometheus-k8s-alertmanager-0 patched

# Get the new container image version.
$ kubectl get pods -n monitoring ${PNAME} -o=jsonpath="{.spec.containers[?(@.name==\"${CNAME}\")].image}{\"|\"}{.status.containerStatuses[?(@.name==\"${CNAME}\")].state}"; echo
---
alertmanager:v0.24.1|{"waiting":{"message":"Back-off pulling image \"alertmanager:v0.25.1\"","reason":"ImagePullBackOff"}}

# Get current pod state
$ kubectl -n monitoring get pod alertmanager-prometheus-k8s-alertmanager-0
---
NAME                                         READY   STATUS         RESTARTS      AGE
alertmanager-prometheus-k8s-alertmanager-0   1/2     ErrImagePull   1 (75s ago)   4m26skubectl get pods -n monitoring ${PNAME} -o=jsonpath="{.spec.containers[?(@.name==\"${CNAME}\")].image}{\"|\"}{.status.containerStatuses[?(@.name==\"${CNAME}\")].state}"; echo
alertmanager:v0.24.1|{"waiting":{"message":"Back-off pulling image \"alertmanager:v0.25.1\"","reason":"ImagePullBackOff"}}