can generate initramfs from busybox

Signed-off-by: Nico Schottelius <nico@wurzel.schottelius.org>

hacking/v3-busybox/init

@@ -0,0 +1,60 @@
+#!/bin/sh
+
+#Mount things needed by this script
+mount -t proc proc /proc
+mount -t sysfs sysfs /sys
+
+#Disable kernel messages from popping onto the screen
+echo 0 > /proc/sys/kernel/printk
+
+#Create all the symlinks to /bin/busybox
+busybox --install -s
+
+#Create device nodes
+mknod /dev/null c 1 3
+mknod /dev/tty c 5 0
+mdev -s
+
+#Function for parsing command line options with "=" in them
+# get_opt("init=/sbin/init") will return "/sbin/init"
+get_opt() {
+    echo "$@" | cut -d "=" -f 2
+}
+
+#Defaults
+init="/sbin/init"
+root="/dev/hda1"
+
+#Process command line options
+for i in $(cat /proc/cmdline); do
+    case $i in
+        root\=*)
+            root=$(get_opt $i)
+            ;;
+        init\=*)
+            init=$(get_opt $i)
+            ;;
+    esac
+done
+
+
+exec sh
+
+# Skipping the rest
+
+#Mount the root device
+mount "${root}" /newroot
+
+#Check if $init exists and is executable
+if [[ -x "/newroot/${init}" ]] ; then
+    #Unmount all other mounts so that the ram used by
+    #the initramfs can be cleared after switch_root
+    umount /sys /proc
+    
+    #Switch to the new root and execute init
+    exec switch_root /newroot "${init}"
+fi
+
+#This will only be run if the exec above failed
+echo "Failed to switch_root, dropping to a shell"
+exec sh