Is there a way to replace
/dev/null device with a regular file (or a device that appends to a file, perhaps)? How much data is written to it?
(This slightly odd question is partially inspired by this..)
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:
Then create a replacement file with the same name and some adequate permissions:
You may now visualize what is sent to /dev/null:
Finally to bring back /dev/null to its normal behaviour:
Some linuxes AFAIK have special device filesystems - devfs; udev - that may complicate this simple procedure.
You can delete /dev/null and touch it as root, then restore it's permissions.
The special device goes away and you get a file instead.