Container Lifecycle Events

Container lifecycle events track the state transitions of a container from creation to termination.

Container States

Waiting

Container is not yet running. Reasons include:

• PullBackOff - Failed to pull image
• CrashLoopBackOff - Container keeps crashing
• CreateContainerConfigError - Invalid config
• ImagePullBackOff - Can't access image registry

kubectl describe pod <pod-name>
# Shows: State: Waiting, Reason: ImagePullBackOff

Running

Container is executing and healthy.

State:
  Running
  Started: 2026-01-03T11:00:00Z

Terminated

Container has finished execution. Can be due to:

• Successful exit (exit code 0)
• Failure (non-zero exit code)
• Signal (SIGKILL, SIGTERM)
• Resource limit exceeded

State:
  Terminated
  Exit Code: 137  # SIGKILL
  Reason: OOMKilled
  Message: Out of memory

Lifecycle Hooks (Related)

postStart

Runs right after container starts (not guaranteed before ENTRYPOINT).

lifecycle:
  postStart:
    exec:
      command: ["/bin/sh", "-c", "echo 'Started'"]

preStop

Runs before container is terminated.

lifecycle:
  preStop:
    exec:
      command: ["/bin/sh", "-c", "sleep 15"]

Monitoring Container Lifecycle

# View detailed container state
kubectl describe pod <pod-name>

# Watch state transitions in real-time
kubectl get pods -w

# Check container logs
kubectl logs <pod-name> <container-name>

# View previous logs (if container restarted)
kubectl logs <pod-name> <container-name> --previous

Exit Codes and Signals

Exit Code	Meaning
0	Success
1-127	Application error
128+N	Killed by signal N
137	SIGKILL (OOMKilled)
143	SIGTERM (Graceful shutdown)

Example: Tracking Lifecycle

# Pod starts
kubectl get pods
# NAME              READY   STATUS
# myapp-abc123      0/1     Pending

# Container is pulling image
# STATUS: PullImage

# Container is running
# READY: 1/1, STATUS: Running

# Container crashes
# READY: 0/1, STATUS: CrashLoopBackOff
# Check logs: kubectl logs <pod-name>

Restarting Container vs Pod

• Container restart - Only the container restarts, increment restart count
• Pod restart - Entire Pod is terminated and recreated

Container restarts (controlled by RestartPolicy) are less disruptive than Pod restarts.