Both containers and virtual machines let you run isolated workloads on shared hardware, but they work at different layers. Understanding containers vs virtual machines helps you pick the right tool for an app, a VPS or a whole hosting platform.
Before you start
- Read what virtualization is for the basic terms.
How virtual machines work
A VM emulates a full computer. A hypervisor such as KVM gives each VM virtual hardware, and the VM boots its own kernel and operating system. A Windows VM and a Linux VM can sit side by side on the same host.
How containers work
A container is a group of processes isolated by Linux kernel features: namespaces (separate views of processes, network and filesystems) and cgroups (resource limits). All containers share the host's kernel. Docker packages one application per container; LXC and LXD run a full Linux userspace that feels like a lightweight VM.
Containers vs virtual machines compared
| Containers | Virtual machines | |
|---|---|---|
| Kernel | Shared with host | Own kernel per VM |
| Guest OS | Linux only on a Linux host | Any OS (Linux, Windows, BSD) |
| Startup | Milliseconds to seconds | Seconds to minutes |
| Overhead | Very low, high density | Higher, reserved RAM per VM |
| Isolation | Process-level; a kernel bug affects all | Hardware-level, stronger boundary |
| Image size | Megabytes | Gigabytes |
| Best for | Microservices, CI, app packaging | Multi-tenant hosting, mixed OSes, full control |
When to use each
- Containers: deploying web apps, APIs and databases reproducibly; running many small services on one server; CI/CD.
- Virtual machines: selling or renting servers to different customers, running Windows, needing a custom kernel or modules, or strong security boundaries.
- Both together: the most common pattern. Rent a KVM VPS, then run Docker inside it. You get VM isolation from neighbours and container convenience for your apps.
Security notes
- Do not run untrusted code in containers with
--privilegedor a mounted Docker socket. - Use rootless or user-namespaced containers where possible.
- For untrusted multi-tenant workloads, prefer VMs or lightweight VM runtimes such as Kata Containers or Firecracker.
Frequently asked questions
Can I run Docker on a VPS?
Yes, on any KVM VPS. On older OpenVZ VPSs Docker may be limited because the kernel is shared with the host.
Are containers less secure than VMs?
Their isolation boundary is thinner because the kernel is shared. Properly configured they are safe for your own apps, but VMs are better for separating untrusted tenants.
Is LXC a container or a VM?
A container. It behaves like a small VM with init and services, but it still shares the host kernel.