Troubleshooting: diagnosing and resetting clusters

You can diagnose or check clusters to debug issues and capture a snapshot of the cluster state. Additionally, if you have partially succeeded with an installation, but the cluster returns errors, or is not performing properly, you can try to reset the cluster.

Diagnosing clusters with bmctl check cluster

You can capture the state of your created clusters with the bmctl check cluster command. The flags for the commmand let you choose the diagnostic scope of the command so you can get focused information.

The diagnostic information can help you discover issues and debug your deployments more effectively. The command captures all relevant cluster and node configuration files for your defined scope, and then packages the information into a single tar archive.

bmctl check cluster --snapshot --cluster CLUSTER_NAME --admin-kubeconfig ADMIN_KUBECONFIG

This command outputs a tar archive that includes relevant debug information from all system components and machines in the cluster you specified.

ADMIN_KUBECONFIGspecifies the path to the kubeconfig file, and CLUSTER_NAME specifies the name of the cluster.

You can change the scope of the diagnostic information collected with the following command flags:

  • The --snapshot-scenario all flag increases the scope of the diagnostic snapshot to include all the Pods in the specified cluster:
bmctl check cluster --snapshot --snapshot-scenario all --cluster CLUSTER_NAME --admin-kubeconfig ADMIN_KUBECONFIG
  • The --snapshot-dry-run flag works in conjunction with the --snapshot-config string flag. Use the --snapshot-dry-run flag to output a configuration file that you can modify to define a custom diagnostic scope. Your scope can include specific pods, namespaces, or node commands.

After you modify the output file created with the --snapshot-dry-run flag, you can use it as input to diagnose your specific scope with the --snapshot-config string flag, described below. If you omit this flag, a default configuration is applied.

bmctl check cluster --snapshot --snapshot-dry-run --cluster CLUSTER_NAME --admin-kubeconfig ADMIN_KUBECONFIG
  • The --snapshot-config flag tells the bmctl command to use the scope options specified in a snapshot configuration file. Generally, you create the snapshot configuration file with the --snapshot-dry-run flag.
bmctl check cluster --snapshot --snapshot-config SNAPSHOT_CONFIG_FILE --cluster CLUSTER_NAME --admin-kubeconfig ADMIN_KUBECONFIG

Resetting clusters with bmctl reset cluster

When a cluster fails to install correctly, you can try to return the nodes to a clean state by resetting it. Then you can re-install the cluster after making configuration changes.

To reset a cluster, issue the following command:

bmctl reset --cluster CLUSTER_NAME

The reset command applies to the entire cluster. There is no option to target a subset of nodes in a cluster.

Output from the command looks similar to this sample:

bmctl reset -c cluster1
Creating bootstrap cluster... OK
Deleting GKE Hub member admin in project my-gcp-project...
Successfully deleted GKE Hub member admin in project my-gcp-project
Loading images... OK
Starting reset jobs...
Resetting: 1    Completed: 0    Failed: 0
...
Resetting: 0    Completed: 1    Failed: 0
Flushing logs... OK

Reset cluster details

During the reset operation, bmctl first attempts to delete the GKE hub membership registration, and then cleans up the affected nodes.

During the reset, storage mounts and data from the anthos-system StorageClass are also deleted.

For all nodes, bmctl runs kubeadm reset, removes the tunnel interfaces used for cluster networking, and deletes the following directories:

  • /etc/kubernetes
  • /etc/cni/net.d
  • /root/.kube
  • /var/lib/kubelet

For load balancer nodes, bmctl also performs the following actions:

  • Disables keepalived and haproxy services
  • Deletes the configuration files for keepalived and haproxy

The reset tool expects the cluster configuration file to be at the following location under the current working directory: 

bmctl-workspace/cluster name/cluster name.yaml