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+# Preparing Linux
+
+To boot Linux, a kernel image (`vmlinuz`) and a suitable initial RAM disk
+(`initrd.img`) need to be created.
+
+## Build the kernel
+
+The Linux kernel for the primary VM can be built using the following
+command-line:
+
+``` shell
+git clone https://github.com/torvalds/linux.git
+cd linux
+ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- make defconfig
+ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- make -j24
+```
+
+The compiled image is stored in `arch/arm64/boot/Image`. This will later be
+copied to the Hafnium RAM disk's root as `vmlinuz`.
+
+## Build the kernel Module
+
+From the Hafnium root directory, the following commands can be used to compile
+the kernel module, replacing `<kernel-path>` with the path to the kernel checked
+out in the previous section:
+
+``` shell
+cd hafnium/driver/linux/
+ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- KERNEL_PATH=<kernel-path> make
+```
+
+The compiled module is called `hafnium.ko`, and will later be copied into the
+RAM disk for Linux.
+
+## Build Busybox
+
+To make Linux useful, it needs a shell. These following instructions will
+construct a file system for the Linux RAM disk with the BusyBox shell as the
+init process.
+
+``` shell
+git clone git://busybox.net/busybox.git
+cd busybox
+ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- make defconfig
+ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- make menuconfig
+```
+
+At this point you should ensure that the option `Settings > Build static binary
+(no shared libs)` is selected. Then you can proceed with the following commands:
+
+``` shell
+ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- make -j24
+ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- make install
+cd _install
+mkdir proc
+mkdir sys
+mkdir -p etc/init.d
+cat <<EOF > etc/init.d/rcS
+#!bin/sh
+mount -t proc none /proc
+mount -t sysfs none /sys
+EOF
+chmod u+x etc/init.d/rcS
+grep -v tty ../examples/inittab > ./etc/inittab
+```
+
+## Create a RAM disk for Linux
+
+At this point you can copy into the current directory additional files you may
+want in the RAM disk, for example, the kernel module built in the previous
+section. Then run the following commands:
+
+``` shell
+find . | cpio -o -H newc | gzip > ../initrd.img
+cd ..
+```
+
+The resulting file is `initrd.img`. It should be copied to the Hafnium RAM
+disk's root.