Build Kernel

On following build steps, a vmlinux binary of about 30MB will get built. It can be used with firecracker-vm by specifying in kernel_image_path.

Build Steps

• Checkout latest code in current directory or download from https://www.kernel.org/

git clone --depth 1 -b master \
  https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git .

• Create .config file, use firecracker minimal config

wget -O .config \
    https://raw.githubusercontent.com/firecracker-microvm/firecracker/refs/heads/main/resources/guest_configs/microvm-kernel-ci-x86_64-6.1.config

• Add pcie and virtio related flags in .config, without these kernel won't boot (required for attaching block-devices)

## PCIE flags

CONFIG_BLK_MQ_PCI=y
CONFIG_PCI=y
CONFIG_PCI_MMCONFIG=y
CONFIG_PCI_MSI=y
CONFIG_PCIEPORTBUS=y
CONFIG_VIRTIO_PCI=y
CONFIG_PCI_HOST_COMMON=y
CONFIG_PCI_HOST_GENERIC=y


# VIRTIO flags
CONFIG_VIRTIO_MEM=y
CONFIG_STRICT_DEVMEM=y

• Do oldconfig

make oldconfig

• Perform build

make -j $(nproc --all)

Refer

• https://docs.kernel.org/admin-guide/quickly-build-trimmed-linux.html