kubernetes notes

• pod

  • smallest deployable unit: a logical host
  • shared: same PID space, same IP:PORT space, same hostname
  • has unique ip
  • can have template
  • ephemeral
  • 1 or more containers in pod
  • 0 or more volumes
    • volumes can be private to a container
    • or shared across containers in a pod
  • a set of pods forms: an app, a service, or a layer
  • has labels: can be used to select a set of pods
  • has annotations: k-v map
  • not for running multiple instance of the same app
  • phase: Pending (downloading image etc), Running, Succeeded, Failed
  • can be probed: LivenessProbe and ReadinessProbe
  • restart policy: Always, OnFailure, Never
  • once bound to a node, will never be rebound

• scheduler

  • bind pod to node

• kubelet

  • kubernetes' node agent
  • restart failed containers

• kube-proxy

  • each node runs a proxy

• replication controller

  • restarts failed machine or pods
  • creates pod from templates

• service

  • a set of pods that forms a service
  • internal service defined using label selector
  • DNS cluster add-on
  • assign each service a DNS name
  • can define external services

• volumes

  • host path
  • aws ebs

• namespace

  • teamDental vs teamXXX?
  • all names are unique under its namespace
  • UID is always unique