When you start using Proxmox VE (PVE), one of the first questions you’ll likely ask is:

“Should I deploy this service as a Container (CT) or a Virtual Machine (VM)?”

When I first began working with PVE, I was attracted by the lightweight nature of Containers and tried to deploy almost everything as a CT. However, as I started hosting more complex services such as Docker, Mail Servers, and development platforms, I realized that the choice isn’t about which technology is better—it’s about selecting the right tool for the right workload.

This article summarizes the key differences between CT and VM, along with the deployment strategy I currently use in production and laboratory environments.

What is a Virtual Machine (VM)?

A Virtual Machine can be thought of as:

A complete computer running inside another computer.

Each VM has its own:

BIOS / UEFI
Virtual CPU
Virtual Memory
Virtual Disk
Operating System
Kernel

From the operating system’s perspective, a VM behaves almost exactly like a physical server.

Advantages

Supports almost any operating system (Linux, Windows, BSD)
Complete hardware and kernel isolation
Excellent compatibility
Supports PCI Passthrough, GPU, USB devices, and other hardware features
Ideal for Docker, Kubernetes, and enterprise applications

Disadvantages

Higher memory consumption
Longer boot time
Greater system overhead

What is a Container (CT)?

A Proxmox Container is based on Linux Containers (LXC).

Unlike a VM, a Container does not have its own kernel. Instead, it shares the Linux kernel of the Proxmox host.

It is best described as:

An isolated Linux user-space environment sharing the host kernel.

Because there is no hardware virtualization layer, Containers offer several significant advantages.

Advantages

Boots within seconds
Extremely low memory usage
Near bare-metal CPU performance
Very fast deployment

Limitations

Linux only
Cannot run Windows
No PCI Passthrough
Limited access to certain kernel features

CT vs VM Comparison

Feature	Container (CT)	Virtual Machine (VM)
Operating System	Linux only	Linux, Windows, BSD
Kernel	Shared Host Kernel	Dedicated Kernel
Boot Time	Very Fast	Slower
Memory Usage	Low	Higher
CPU Efficiency	Near Native	Slight Overhead
Isolation	Moderate	Strong
Docker Compatibility	Limited	Excellent
GPU / PCI Support	No	Yes
Snapshots	Yes	Yes
Backup Support	Yes	Yes

When Should You Choose a Container?

In my experience, Containers are an excellent choice when the service is:

Linux-based
Lightweight
Performs a single function
Does not require Docker
Does not require custom kernel modules

Typical examples include:

DNS Server
NTP Server
OpenLDAP
HAProxy
Nginx Reverse Proxy
Redis
Grafana
Prometheus
LibreNMS
Zabbix Proxy

These services generally consume minimal resources and operate very reliably inside Containers.

When Should You Choose a Virtual Machine?

I typically choose a VM whenever any of the following requirements exist:

Windows Server
Docker
Kubernetes
Mail Server
AI / Machine Learning workloads
GPU acceleration
PCI Passthrough
Custom kernel modules

Typical examples include:

Docker Host
GitLab
Jenkins
Mail Server
SQL Server
PostgreSQL
Elasticsearch
OpenSearch

Can Docker Run Inside a Container?

The short answer is:

Yes—but I would not recommend it for production environments.

Docker is already a container platform.

Running Docker inside an LXC Container creates a nested container environment:

Docker
   ↓
LXC Container
   ↓
Linux Host

This is commonly referred to as:

Container inside Container

Although it is technically supported with additional configuration, it often introduces complexity related to:

AppArmor
cgroups
overlay2
iptables
Privileged Mode
Nesting
Linux Kernel Capabilities

My Practical Experience

I previously experimented with running Docker inside an LXC Container.

Almost immediately I encountered issues such as:

hello-world failing to execute
AppArmor permission restrictions
overlay2 storage driver errors
OCI Runtime errors
net.ipv4.ip_unprivileged_port_start permission problems

While most of these issues have workarounds, every Linux distribution, Docker release, and kernel update may introduce new compatibility challenges.

Eventually, I migrated Docker to a Virtual Machine.

The result was immediate:

Everything worked as expected.
Maintenance became much easier.
Stability improved significantly.

Since then, my deployment strategy has been very simple:

All Docker workloads are deployed on Virtual Machines.

Resource Consumption

One of the biggest advantages of Containers is resource efficiency.

Consider four common infrastructure services:

DNS
NTP
LDAP
Syslog

Deploying all of them as Virtual Machines may require several gigabytes of memory.

Deploying the same services as Containers usually consumes only a few hundred megabytes in total.

For lightweight infrastructure services, Containers can dramatically improve server density and overall resource utilization.

My Recommended Deployment Strategy

Use Containers for:

DNS
NTP
OpenLDAP
Reverse Proxy
Grafana
Prometheus
LibreNMS

Use Virtual Machines for:

Docker
Mail Server
AI Server
Windows Server
GitLab
PostgreSQL
SQL Server

In short:

Containers are ideal for lightweight, single-purpose Linux services, while Virtual Machines are the better choice whenever maximum compatibility, hardware support, or complete operating system isolation is required.

Final Thoughts

Neither Containers nor Virtual Machines are inherently better than the other.

Each technology has its strengths and is designed for different scenarios.

My current deployment philosophy is straightforward:

Deploy lightweight infrastructure services such as DNS, NTP, LDAP, and monitoring tools as Containers to maximize efficiency.
Deploy Docker, AI workloads, enterprise applications, databases, and Windows servers as Virtual Machines to ensure the best compatibility and long-term stability.

This hybrid approach has proven to be both efficient and reliable, allowing me to take full advantage of Proxmox VE while avoiding many of the compatibility issues that often arise when choosing the wrong virtualization method.