Direct comparison
Docker vs Virtual Machine: Kernel and Isolation
Docker vs virtual machine compared: kernel sharing, isolation, size, updates and what each pins for reproducible research, from Docker and Microsoft docs.
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How do Virtual machine, Docker container compare side by side?
The table below compares Virtual machine, Docker container across 12 procurement-relevant dimensions, from what is isolated through source.
Side-by-side comparison
| Dimension | Virtual machine | Docker container |
|---|---|---|
| What is isolated | A full virtual machine: "an entire operating system with its own kernel, hardware drivers, programs, and applications." | A process: "simply an isolated process with all of the files it needs to run." |
| Kernel | Each VM runs its own kernel, as part of a complete operating system. | Containers share the host OS kernel, "each running as isolated processes in user space." |
| What each copy includes | "A full copy of an operating system, the application, necessary binaries and libraries." | The application and its files; the operating system kernel is not packaged in. |
| Typical size | Tens of GBs, per Docker. | Container images are typically tens of MBs, per Docker. |
| Boot | Docker says VMs "can also be slow to boot." No figure is given. | Docker gives no startup time for containers, so none is stated here. |
| Security boundary | Complete isolation from the host OS and other VMs; Microsoft calls this useful "when a strong security boundary is critical." | Typically lightweight isolation; Microsoft says it does not provide as strong a security boundary as a VM. |
| Guest OS compatibility | Runs just about any operating system. | On Windows, runs on the same operating system version as the host (Microsoft, Windows containers). |
| Updating | Install OS updates on each VM. | Edit the base image in the Dockerfile, rebuild, push and redeploy. |
| What a copy pins for reproducibility | The whole stack including the kernel, because the VM carries its own. | The application environment only; the kernel comes from the host, so it is not pinned by the image. |
| Typical host | Hypervisor on hardware. | Often a VM itself: Microsoft notes many container deployments use VMs as the host OS, especially in the cloud. Docker Desktop on Windows defaults to WSL 2; its Hyper-V backend needs hardware virtualization enabled. |
| When to pick each | Pick a VM when a strong security boundary is critical or you need a different guest operating system. | Pick a container when you want to run more applications on less infrastructure by sharing one kernel, and want updates handled by rebuilding an image. |
| Source | Docker, Docker Docs and Microsoft Learn pages cited below, all read 2026-10-29. | Same sources; NIST SP 800-190 (Sept 2017) describes containers as a form of operating system virtualization. |
Common questions
Common questions about Virtual machine vs Docker container
Is Docker a virtual machine?
+
No. Docker describes a container as an isolated process that shares the host kernel, while a VM is an entire operating system with its own kernel. Docker calls itself a cost-effective alternative to hypervisor-based virtual machines.
Do containers have their own kernel?
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No. Docker states that containers share the OS kernel with other containers, each running as isolated processes in user space. On Windows, Hyper-V isolation mode runs each container in a lightweight VM, which changes that.
Is a container less secure than a VM?
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Microsoft says containers typically provide lightweight isolation and do not give as strong a security boundary as a VM, and that a VM suits cases where a strong security boundary is critical.
Can you run Docker inside a VM?
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Yes, and it is common. Microsoft notes many container deployments use VMs as the host operating system, especially in the cloud. Docker Desktop on Windows uses WSL 2 by default.
Which is better for reproducible research?
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Neither is better in general. A VM image carries its own kernel, so it pins the whole stack; a container image does not pin the host kernel it runs on. Record which one you used and its image or Dockerfile.
Going deeper
