ACRN Hypervisor vs Firecracker

ACRN Hypervisor is a free, open-source Type 1 hypervisor stack for embedded IoT development. It runs directly on Intel x86 bare-metal hardware and supports Linux, Windows and RTOS guests such as Zephyr; the project also lists VxWorks, Xenomai, Celadon and Android. CPU, I/O and networking virtualization are included, with I/O mediators for sharing graphics and audio across virtual machines. Resource partitioning is designed for safety-critical and non-safety-critical domains to coexist on one system-on-chip. The ACRN Device Model provides virtual device emulation. The project describes a codebase under 40K lines and reports low latency, fast boot times and responsive hardware communication. ACRN uses the BSD 3-Clause license, offers a command-line management interface and supports nested virtualization. Source code is maintained in a public GitHub repository with online documentation. Community help is available through mailing lists, IRC channels and monthly technical meetings.

Firecracker is open-source virtualization software for running container and function workloads in lightweight microVMs. It uses Linux KVM hardware virtualization to isolate each workload and exposes only five emulated devices, a design intended to reduce attack surface. MicroVMs start in under 125 ms, add under 5 MiB of memory overhead each, and a host can create up to 150 per second while packing thousands onto one server. A RESTful API configures and starts the VMs, while rate limiters govern network and storage bandwidth and operations. The companion jailer adds Linux user-space security barriers. Firecracker supports Linux hosts and guests with kernel versions 4.14 and above, plus OSv guests, on production 64-bit Intel, AMD, and Arm CPUs with hardware virtualization. VM snapshots are supported, but GPU acceleration is not. It is free under Apache 2.0, with integrations including containerd, Kata Containers, and Fly.io.