mkdir -p os/rootfs
cd os/rootfs

#create base file system
mkdir dev proc sys tmp bin
sudo mknod dev/console c 5 1

#copy buysbox and link all applications
cp /usr/bin/busybox bin
./bin/busybox busybox --install ./bin/

#create init script
echo '#!/bin/sh
mount -t proc proc /proc 
mount -t sysfs sysfs /sys 
mount -t devtmpfs udev /dev

/bin/sh
poweroff -f' > init
chmod +x init

#create initrd
find . | cpio -H newc -o | gzip > ../rootfs.cpio.gz

cd ../

#copy kernel from current system
cp "$(ls /boot/vmlinuz-*|tail -n1)" linux

#run virtual machine
qemu-system-x86_64 -enable-kvm -kernel linux -initrd rootfs.cpio.gz
#or run it without GUI in current shell
qemu-system-x86_64 -enable-kvm -kernel linux -initrd rootfs.cpio.gz -nographic -append 'console=ttyS0'