diff --git a/README.md b/README.md
index eb23aa4..10aba85 100644
--- a/README.md
+++ b/README.md
@@ -120,6 +120,19 @@ TODO: Ctrl + C kills the emulator, it is not sent to guest processes. See:
 - <https://github.com/cloudius-systems/osv/issues/49>
 - <https://unix.stackexchange.com/questions/167165/how-to-pass-ctrl-c-in-qemu>
 
+## Automatic startup commands
+
+When debugging a module, it becomes tedious to wait for build and re-type:
+
+    root
+    /mymod.sh
+
+Instead, you can add your test commands to:
+
+    rootfs_overlay/etc/init.d/S99
+
+and they will be run automatically before the login prompt.
+
 ## Debugging
 
 To GDB the Linux kernel, first run:
diff --git a/rootfs_overlay/etc/init.d/S99 b/rootfs_overlay/etc/init.d/S99
new file mode 100755
index 0000000..28ee2ab
--- /dev/null
+++ b/rootfs_overlay/etc/init.d/S99
@@ -0,0 +1,4 @@
+#!/bin/sh
+echo 'S99'
+# insmod /hello.ko
+exit 0