Kata Containers inside Docker-in-Docker

A VM-based container runtime (Kata Containers with Firecracker VMM) running inside a Docker-in-Docker (DinD) container. This setup provides lightweight virtual machines with strong security isolation while maintaining container-like performance and simplicity. Kata Containers can use multiple hypervisors (QEMU, Firecracker, Cloud Hypervisor), and this image includes Firecracker by default for optimal performance.

Features

✅ Complete Kata Containers runtime with official installation
✅ Firecracker VMM for lightweight VM isolation
✅ QEMU fallback support
✅ Docker-in-Docker support for managing containers
✅ VM-based container isolation with hardware security
✅ Resource limits to prevent system exhaustion
✅ Health checks for runtime readiness
✅ Persistent storage for Kata and Docker data
✅ Configurable logging levels
✅ Compatible with Kubernetes via RuntimeClass

Prerequisites

Critical Requirements:

Docker Engine 20.10+
Docker Compose 2.0+
Host machine must support nested virtualization (KVM)
/dev/kvm device available on the host
/lib/modules available on the host (for kernel module verification)
At least 2 CPU cores and 4GB RAM available
Privileged container support required

Verify Host Prerequisites

# Check if KVM is available
ls -l /dev/kvm

# For Intel CPUs, verify nested virtualization is enabled
cat /sys/module/kvm_intel/parameters/nested
# Should output 'Y' or '1'. If not:
# sudo modprobe -r kvm_intel
# sudo modprobe kvm_intel nested=1

Quick Start

Copy the environment file:
```
cp .env.example .env
```
(Optional) Customize the configuration in .env
Build and start the service:
```
docker compose up -d --build
```
Wait for Kata runtime to be ready:
```
docker compose logs -f kata-dind
```

Access the Docker daemon inside:

# Get the container ID
docker compose ps

# Execute commands inside the container
docker compose exec kata-dind docker ps

# Run a container with Kata runtime (Firecracker)
docker compose exec kata-dind docker run --rm --runtime=kata-fc debian:bookworm uname -a

# Or run with QEMU (fallback)
docker compose exec kata-dind docker run --rm --runtime=kata debian:bookworm uname -a

Configuration

Environment Variables

Variable	Default	Description
`DEBIAN_VERSION`	`13.2-slim`	Base Debian version
`KATA_VERSION`	`3.24.0`	Kata Containers version
`FIRECRACKER_VERSION`	`1.10.1`	Version of Firecracker VMM to install
`KATA_DIND_VERSION`	`0.2.0`	Built image version tag
`TZ`	`UTC`	Timezone for the container
`KATA_LOGGING_LEVEL`	`info`	Kata logging level (debug, info, warn, error)
`KATA_DIND_CPU_LIMIT`	`2.00`	CPU limit in cores
`KATA_DIND_MEMORY_LIMIT`	`4G`	Memory limit
`KATA_DIND_CPU_RESERVATION`	`0.50`	CPU reservation in cores
`KATA_DIND_MEMORY_RESERVATION`	`1G`	Memory reservation

Usage Examples

Running a Secure Container

docker compose exec kata-dind docker run -it --rm --runtime=kata-fc alpine sh

Checking Runtime Information

docker compose exec kata-dind docker info | grep -i runtime

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