Move root filesystem from rootfs to tmpfs

deploy/iso/minikube-iso/board/coreos/minikube/rootfs-overlay/init

@@ -0,0 +1,13 @@
+#!/bin/sh
+mkdir /sysroot
+# the value 90% borrowed from tcl via boot2docker
+mount -t tmpfs -o size=90% tmpfs /sysroot
+# copy from rootfs, to be able to do switch_root(8)
+tar -C / --exclude=sysroot -cf - . | tar -C /sysroot/ -xf -
+
+# devtmpfs does not get automounted for initramfs
+/bin/mount -t devtmpfs devtmpfs /sysroot/dev
+exec 0</sysroot/dev/console
+exec 1>/sysroot/dev/console
+exec 2>/sysroot/dev/console
+exec /sbin/switch_root /sysroot /sbin/init "$@"