Kubernetes errors

• 0/3 nodes are available: Insufficient cpuThe scheduler cannot place the pod on any node because no node has enough unreserved CPU (or memory) to satisfy the pod's resource requests. Requests count, not actual usage.
• CrashLoopBackOffThe container starts, exits, and Kubernetes keeps restarting it with growing delays. The reason is in the previous container's logs and in kubectl describe.
• CreateContainerConfigErrorThe image pulled fine, but the kubelet couldn't build the container's configuration. Almost always a ConfigMap or Secret (or a key inside one) referenced by env/envFrom doesn't exist in the pod's namespace, or a securityContext rule can't be satisfied.
• error converting YAML to JSON: yaml: line N: mapping values are not allowed in this contextkubectl (or Helm) couldn't parse your manifest because the YAML is malformed — usually a missing space after a colon, wrong indentation, or an unquoted value containing ": ". The line number points at or just after the problem.
• Error from server (Forbidden): User cannot list resource in API group at the cluster scopeKubernetes authenticated you, but RBAC doesn't grant your user or service account the verb (get, list, create...) on that resource in that namespace. Fix the Role/ClusterRole and binding, or use the right namespace or context.
• error: resource mapping not found ... no matches for kind "Deployment" in version "extensions/v1beta1"The cluster has no API for that kind/apiVersion combination. Either the apiVersion was removed in your Kubernetes version (old manifests and Helm charts), or the kind belongs to a CRD that isn't installed yet.
• error: You must be logged in to the server (Unauthorized)The API server rejected kubectl's credentials as invalid (HTTP 401). The token or client certificate in your kubeconfig expired, belongs to another cluster, or your cloud CLI login lapsed.
• ImagePullBackOff / ErrImagePullThe node couldn't download the container image. Wrong name or tag, a private registry without imagePullSecrets, or rate limits.
• OOMKilled (exit code 137)The container used more memory than its memory limit, so the kernel's OOM killer terminated it. Raise the limit, or reduce the app's memory use and make the runtime respect the container limit.
• pod has unbound immediate PersistentVolumeClaimsThe pod references a PersistentVolumeClaim that is still Pending — no PersistentVolume has been bound to it — so the scheduler can't place the pod. Usually there's no default StorageClass, no provisioner, or no matching PV.
• The connection to the server localhost:8080 was refused - did you specify the right host or port?kubectl found no kubeconfig, so it fell back to its built-in default of http://localhost:8080. Point kubectl at your cluster's kubeconfig.
• x509: certificate has expired or is not yet validA TLS certificate in the chain is outside its validity period. On kubeadm clusters this is usually the control-plane certificates (valid 1 year) or the admin kubeconfig expiring; it can also be a wrong system clock.