debug boot script

[ray]

I want to debug an init cript in /etc/rcS.d That script outputs some
messages using echo, so the messages should be printed to the stdout. I
guess the redirect mechanism provided by shell is supposed to work in order
to grab these messages into a file. To verify it, I created a test script in
/etc/rcS.d, writing the content as below:
echo "hello" > /tmp/message
But when I boot up the system, nothing happened. Can somebody give me any
hint?