Pod lifecycle states in Kubernetes - Step-by-Step Execution

Process Flow - Pod lifecycle states

Pending

↓

Running

↓

Succeeded

↓

Failed

↓

Unknown

This flow shows how a Kubernetes Pod moves through phases from Pending to terminal states.

Execution Sample

Kubernetes

kubectl get pod mypod -o jsonpath='{.status.phase}'
# Output shows current Pod state

This command checks the current lifecycle state of a Pod named 'mypod'.

Process Table

Step	Pod State	Condition	Action	Result
1	Pending	Pod object created in cluster	Start scheduling	Pod enters Pending
2	Pending	Waiting for container images and node assignment	Schedule Pod to node	Pod moves to Running
3	Running	Containers are running	Monitor container status	Pod stays Running or moves to terminal state
4	Running	Container exits with code 0	Mark Pod as Succeeded	Pod moves to Succeeded
5	Running	Container exits with error code	Mark Pod as Failed	Pod moves to Failed
6	Running	Status unknown due to node issues	Mark Pod as Unknown	Pod moves to Unknown
7	Succeeded/Failed/Unknown	Pod lifecycle ends	Cleanup resources	Pod remains in terminal state

💡 Pod reaches a terminal state (Succeeded, Failed, or Unknown) and is cleaned up.

Status Tracker

Pod State	Start	After Step 1	After Step 2	After Step 3	After Step 4/5/6	Final
podPhase	None	Pending	Running	Running	Succeeded/Failed/Unknown	Succeeded/Failed/Unknown

Key Moments - 3 Insights

Why does a Pod stay in Pending state for a while?

Because the Pod is waiting for the scheduler to assign it to a node and for container images to be pulled, as shown in execution_table row 2.

What causes a Pod to move from Running to Succeeded?

When all containers in the Pod exit successfully with code 0, the Pod phase changes to Succeeded, as shown in execution_table row 4.

What does the Unknown state mean for a Pod?

It means the Pod status cannot be determined, often due to node communication issues, as shown in execution_table row 6.

Visual Quiz - 3 Questions

Look at the execution table, what is the Pod state right after scheduling is complete?

A Running

B Pending

C Succeeded

D Created

💡 Hint

Check row 2 and 3 in the execution_table where Pending moves to Running after scheduling.

At which step does the Pod enter a terminal state?

A Step 3

B Step 4

C Step 7

D Step 2

💡 Hint

Look at the exit_note and row 7 where Pod is cleaned up after terminal states.

If a container crashes with an error, which Pod state will it move to?

A Succeeded

B Failed

C Pending

D Unknown

💡 Hint

See execution_table row 5 where container error leads to Failed state.

Concept Snapshot

Pod lifecycle states:
- Pending: Waiting for scheduling and images
- Running: Containers running
- Succeeded: Containers exited successfully
- Failed: Containers exited with error
- Unknown: Status not known

Full Transcript

A Kubernetes Pod starts in Pending state when created. It remains in Pending while waiting for scheduling and image download. Once scheduled and containers start, it moves to Running. If containers exit successfully, Pod becomes Succeeded. If containers fail, Pod becomes Failed. If status cannot be determined, Pod is Unknown. Finally, Pod reaches a terminal state and is cleaned up. This flow helps track Pod health and lifecycle.