Kernels

Firecracker requires a kernel image to boot a microVM.

Currently, Firecracker supports uncompressed ELF kernel images on x86_64 while on aarch64 it supports PE formatted images.

For compatibility, it is recommended to use a kernel image that is supported by the Firecracker version you are using. For more information see the Firecracker's Kernel Support Policy

With the default Fireactions installation, the kernel image is located in the /var/lib/fireactions/kernels/<VERSION>/vmlinux path. You can change the kernel image path by modifying the kernel_image_path parameter for each Pool in the Fireactions configuration file.

The latest Firecracker kernel image can be downloaded from the Firecracker CI S3 bucket. The following script can be used to download the latest kernel image for a specific version:

#!/bin/bash

latest=$(wget "http://spec.ccfc.min.s3.amazonaws.com/?prefix=firecracker-ci/v1.10/x86_64/vmlinux-5.10&list-type=2" -O - 2>/dev/null | grep "(?<=<Key>)(firecracker-ci/v1.10/x86_64/vmlinux-5\.10\.[0-9]{3})(?=</Key>)" -o -P)

wget "https://s3.amazonaws.com/spec.ccfc.min/${latest}"

We also provide our own Kernel images, customized for GitHub runners. The configuration can be found here. The kernel images can be downloaded from the following links:

You can also build your own custom kernel image. For more information see the Firecracker documentation.