This chapter contains varions information related to Kubernetes.

Kubernetes#

k8s is an open source container orchestration tool.

Helps you manage containerized applications, in a different environments.

Uncategorized#

ImagePullBackOff Error#

This is a common error message in Kubernetes that occurs when a container running in a pod fails to pull the required image from a container registry.

Init containers#

• Specialized containers that run before app containers in a pod
• init containers can contain utilities or setup scripts not present in app image
• do not support lifecycle, liveness probe, readiness probe or startup probe

Sidecar container#

Container that starts before the main application container and continues to run.

Probe#

• diagnostics performed periodically by the kubelet on a container
• it can be either execution of some code or a network request
• exec – specified command
• grpc – remote procedure call
• http get
• tcp socket

Result (outcomes): success, failure, unknown

Liveness probe#

If fails, kubelet kills the container, and it is subjected to its restart policy/

Readiness probe#

Indicates if container is ready to respond to requests.

If fails, endpoint controller removes pod’s IPs adresses from the endpoints of all services that match the pod.

Startup probe#

Indicates if app is started.

If fails, kubelet kills the container and it is the subject of its restart policy.

Restart policy#

Possible values:

• Always – restart after any termination
• On Failure – only on error
• Never – does not restart terminated container