Init Containers and Sidecar Patterns: Sequential Setup and Co-located Services

Calendar February 21, 2026
Kubernetes
Intermediate
Init-Container-Design, Sidecar-Pattern-Implementation, Pod-Lifecycle-Management, Multi-Container-Debugging
Init-Containers, Sidecars, Pod-Design, Service-Mesh, Log-Shipping, Native-Sidecars
Kubectl

Init Containers and Sidecar Patterns#

A pod can contain more than one container. Init containers run sequentially before the main application starts. Sidecars run alongside the main container for the lifetime of the pod. Together, they enable patterns where setup logic and cross-cutting concerns are separated from application code.

Init Containers#

Init containers are defined in spec.initContainers[] and run in order. Each must exit 0 before the next one starts. If any init container fails, Kubernetes restarts the pod (subject to restartPolicy). The main application containers do not start until every init container has completed successfully.