Is there a way to replace /dev/null with an actual file?

"I would strongly advise against doing so ... depending on your system the resulting file could grow really fast. However, it's quite easy to have fun with a VM.

I will describe how to do this during one session, i.e. everything should be back the way they were after a reboot.

Obviously, this has to be done as root.

First, you need to delete the current /dev/null:

rm /dev/null

Then create a replacement file with the same name and some adequate permissions:

touch /dev/null
chmod 666 /dev/null

You may now visualize what is sent to /dev/null:

tail -f /dev/null

Finally to bring back /dev/null to its normal behaviour:

rm /dev/null
mknod /dev/null c 1 3
chmod 666 /dev/null"

"On OpenBSD:

cd /dev
sudo mv null blah
sudo touch null
sudo chmod a+rwx null
echo foo > /dev/null

Some linuxes AFAIK have special device filesystems - devfs; udev - that may complicate this simple procedure."