Kernel

bhatti uses a custom-built Linux kernel optimized for Firecracker microVMs. The kernel is minimal — only the features needed for sandbox workloads are enabled.

Building

# Clone the kernel source
git clone --depth 1 --branch v6.1 https://github.com/torvalds/linux.git
cd linux

# Apply the bhatti config
cp /path/to/bhatti/kernel/.config .config

# Build
make -j$(nproc) vmlinux

The output vmlinux is an uncompressed kernel binary — Firecracker loads it directly.

Key config choices

The kernel config enables:

• virtio — virtio-blk (rootfs, config drive, volumes), virtio-net (networking), vsock (host↔guest)
• ext4 — filesystem for rootfs and volumes
• devtmpfs — required for /dev device nodes
• PTY — for interactive shell sessions
• process namespaces — for process isolation within the VM
• network — TCP/IP stack, bridge support

The kernel config disables everything unnecessary for a sandbox environment: USB, sound, most filesystems, most network drivers, hardware-specific drivers.

Architecture support

Two kernel configs are maintained:

• vmlinux-arm64 — for Raspberry Pi 5, Graviton, and other ARM64 hosts
• vmlinux-amd64 — for x86_64 bare metal and cloud instances

The correct kernel is selected automatically based on the host architecture.