KCNA Container Orchestration Practice Question
Which two of the following are characteristics of container images built using OCI standards? (Choose two.)
⚠ Common exam trap
KCNA often tests the misconception that containers are 'lightweight VMs' — candidates pick 'full guest OS' or 'requires hypervisor' because they conflate container isolation with virtualization.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
They are portable across different container runtimes
Option A is correct because OCI (Open Container Initiative) image specifications define a runtime-agnostic format, so an image built to OCI standards can be pulled and executed by any OCI-compliant runtime such as containerd, CRI-O, or Docker, not just one vendor's engine. Option B is correct because OCI images are built as a stack of content-addressable layers, each identified by a digest, which allows runtimes and registries to cache and reuse unchanged layers across builds and pulls, reducing storage and transfer overhead. Option C is incorrect because containers share the host kernel and do not bundle a full guest operating system; that characteristic belongs to virtual machines. Option D is incorrect because OCI compliance explicitly enables portability beyond Docker to other runtimes like containerd and CRI-O. Option E is incorrect because containers run directly on the host kernel via namespaces and cgroups, requiring no hypervisor (except in specialized VM-isolated setups, which are not the norm for OCI images).
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
They are portable across different container runtimes
Why this is correct
OCI image specifications define a runtime-agnostic manifest and filesystem bundle, so any compliant runtime (Docker, containerd, CRI-O) can pull and execute the same image. This portability satisfies the stem's requirement by decoupling the artefact from a single vendor's engine.
- ✓
They are composed of layers that can be cached and reused
Why this is correct
OCI images are content-addressed layers; identical layers are stored once and shared across images, so pulls and builds reuse cached layers rather than transferring everything. This layered structure directly delivers the caching and reuse the question asks about.
- ✗
They include a full guest operating system
Why it's wrong here
OCI images package only the application and its user-space dependencies, sharing the host's kernel; a full guest operating system belongs to virtual machine images. It is tempting because images do contain an OS filesystem layer, but that is userland only, not a bootable kernel, which is why containers start in seconds.
- ✗
They can only be run by Docker
Why it's wrong here
The OCI image specification is runtime-neutral, so containerd, CRI-O and podman all execute compliant images; Docker is merely one implementation. It is tempting because Docker popularised the format, but portability across runtimes is precisely the standard's purpose, making vendor lock-in the opposite of its design goal.
- ✗
They require a hypervisor to run
Why it's wrong here
OCI images are user-space bundles of application and libraries sharing the host kernel, so they run under a container runtime such as runc, not a hypervisor. It is tempting because hypervisors underpin virtual machines, which is the correct isolation choice when strong hardware-level separation or a different kernel is required.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CNCF exam blueprint
This KCNA practice question is part of Courseiva's free CNCF certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the KCNA exam.