KCNA Container Orchestration Practice Question
Which of the following is a key difference between containers and virtual machines?
⚠ Common exam trap
CNCF often tests the misconception that containers and VMs are fundamentally similar in kernel sharing, leading candidates to choose Option B, which incorrectly claims both share the host kernel.
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
✓
Containers share the host OS kernel; VMs run a separate guest OS
The key difference is that containers virtualize at the operating system level, sharing the host OS kernel via namespaces and cgroups, while each virtual machine runs a full, separate guest OS on top of a hypervisor. This architectural distinction means containers are more lightweight and start faster, but VMs provide stronger isolation because they do not share the host kernel.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Containers share the host OS kernel; VMs run a separate guest OS
Why this is correct
Containers share the host's kernel and isolate processes, so they carry no guest OS. VMs each run a complete guest operating system on virtualised hardware. This architectural difference explains containers' smaller footprint and faster startup compared with VMs.
- ✗
Both containers and VMs share the host kernel
Why it's wrong here
Containers share the host kernel; VMs each run their own guest kernel via a hypervisor, so this statement inverts the actual distinction. It is tempting because containers do rely on the host kernel, but the option wrongly claims VMs do too, which is precisely what separates the two technologies.
- ✗
Containers have a full guest OS, VMs share the host kernel
Why it's wrong here
This reverses the architecture: containers share the host kernel and carry no guest OS, while VMs each include a full guest OS. It is tempting because VMs do bundle an OS image, but the option swaps the two roles, so neither half matches how containers or VMs actually operate.
- ✗
Containers require a hypervisor, VMs do not
Why it's wrong here
Containers share the host kernel and need no hypervisor; VMs each run a full guest OS on one. The option inverts this, so it fails on the core architectural axis. It would be correct only if it stated that VMs require the hypervisor and containers do not.
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