Init Containers and Startup Order

Workloads / Guide 31 of 103 / Beginner

• Kubernetes1.36.4
• Cluster4 nodes
• Runtimecontainerd 2.2.6
• CNICalico v3.32.1
• TimeAbout 25 min

Timings depend on how quickly images are already cached on the node.

This guide includes

Use this when a container must not start until something else is ready - a migration, a config fetch, a dependency that has to answer first. This matters because init containers run to completion one at a time before any app container starts, which is a guarantee ordinary containers never give you.

• writing initContainers as a separate list and watching them run strictly in order
• reading each init container's logs separately with -c
• finding their end state recorded in initContainerStatuses as Completed rather than Running

Before you start

• A working cluster and kubectl.
• The Pods guide, particularly the multi-container section: init containers share volumes the same way sidecars do.
• Nothing else.

1. 1

   Two init containers and an app that depends on them

2. 2

   Wait for them, then read each log separately

3. 3

   Init containers are Completed, not Running

4. 4

   Clean up

Official sources

• Init containers
• Sidecar containers
• Pod lifecycle
• Resource management for pods and containers