- Master: The system from which you manage your Kubernetes environment.
- Nodes: One or more systems on which containers are deployed by Kubernetes (nodes were previously called minions).
- Pods: A pod defines one or more containers to run, as well as options to the docker run command for each container and labels to define the location of services.
- Services: A service allows a container within a Kubernetes environment to find an application provided by another container by name (label), without knowing its IP address.
- Replication controllers: A replication controller lets you designate that a certain number of pods should be running. (New pods are started until the required number is reached and if a pod dies, a new pod is run to replace it.)
- Networking (flanneld): The flanneld service lets you configure IP address ranges and related setting to be used by Kubernetes. This feature is optional. yaml and json files: The Kubernetes elements we’ll work with are actually created from configuration files in yaml or json formats. this topic focuses primarily on yaml-formatted files.
You will troubleshoot the components just described using these commands in particular:
- kubectl: The kubectl command (run from the master) lets you create, delete, get (list information) and perform other actions on Kubernetes pods, services and replication controllers. You’ll use this command to test your yaml/json files, as well as see the state of the different Kubernetes components.
- systemctl: Specific systemd services must be configured with Kubernetes to facilitate communications between master and nodes. Those services must also be active and enabled.
- journalctl: You can use the journalctl command to check Kubernetes systemd services to follow the processing of those services. You can run it on both the master and nodes to check for Kubernetes failures on those systems. All daemon logging in kubernetes uses the systemd journal.
- etcdctl or curl: The etcd daemon manages the storage of information for the Kubernetes cluster. This service can run on the master or on some other system. You can use the etcdctl command in RHEL or RHEL Atomic Host systems to query that information. You also can use the curl command instead to query the etcd service.
출처: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux_atomic_host/7/html/getting_started_with_kubernetes/troubleshooting_kubernetes
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