When containers started becoming popular, there was one big problem—every company or tool was making their own container format and runtime. This created fragmentation. A container built with one tool sometimes could not run on another. To solve this, in 2015, big players like Docker, CoreOS, and other tech leaders came together and formed the Open Container Initiative (OCI).
The idea was simple: make a set of open, industry standards for container images and runtimes so that containers run the same everywhere.
Why OCI Was Needed
Imagine a world where every car company makes its own fuel type—petrol, diesel, gas, all different. That’s how containers were before OCI. Developers faced:
- Compatibility issues – One container image could not run on different platforms.
- Vendor lock-in – Stuck with one tool or one company’s ecosystem.
- Slower adoption – Teams feared future migrations.
OCI solved this by standardizing container formats just like USB standard made every cable and device connect easily.
Components of OCI
OCI focuses on three main specifications:
-
OCI Image Specification
- Defines how a container image is structured.
- Ensures images are portable, shareable, and immutable.
- Example: A Docker image or Podman image both follow OCI image spec.
-
OCI Runtime Specification
- Defines how to run a container image.
- Sets rules for container lifecycle: create, start, stop, delete.
- Example:
runcis the reference runtime implementation of OCI spec.
-
OCI Distribution Specification
- Defines how images are pushed and pulled from registries.
- Standardizes the API between registries and clients.
- Example: Docker Hub, Harbor, ECR all follow this distribution spec.
How OCI Helps Developers
- Portability – Build once, run anywhere (cloud, bare metal, VM).
- Interoperability – Different tools can talk to each other.
- Future-proofing – No vendor lock-in, your container image will stay valid.
- Community driven – Backed by Linux Foundation, open governance.
OCI in Real World
- Docker images follow OCI image spec.
- Podman also follows OCI standards, so Docker images run without issue.
- Kubernetes relies on OCI-compliant runtimes for running containers.
- Registries like Docker Hub, Amazon ECR, Harbor comply with OCI distribution spec.
This means no matter which platform you use, containers behave the same.
Benefits of OCI Standards
- Consistency across environments.
- Better security due to common auditing and scanning.
- Easier collaboration between teams and companies.
- Ecosystem growth – New tools can join without breaking old ones.
FAQs on Open Container Initiative
Q1. Is OCI a software or a company? Neither—it’s a community project under the Linux Foundation that maintains container standards.
Q2. Do I need to install OCI separately? No, you don’t “install” OCI. It’s already implemented inside tools like Docker, Podman, and Kubernetes.
Q3. What is the relation between Docker and OCI? Docker donated its container runtime (runc) to OCI. Today, Docker images follow OCI standards, making them portable.
Q4. What if a container runtime does not follow OCI? Then you may face compatibility issues. Most modern runtimes follow OCI to avoid this problem.
Q5. Does OCI also cover orchestration like Kubernetes? No, OCI focuses only on container runtime, image, and distribution. Orchestration is handled separately by tools like Kubernetes.