Working with the terminal using a command interface is very fast and effective way of doing stuff. But have you tried working with the terminal, listening to a music via headphones and having a terminal warning or tab-completion beep / bell turned ON at the same time? Well it can be very annoying. Listening to the PC Speaker beeps via headphones is very close to a feeling of hitting your head with a hammer. Even without headphones this beeping bell sound is very annoying.
-bash: /dev/null: Permission denied
Posting the Debian answer for posterity…
sudo su \
&& rm -rf /dev/null \
&& mknod /dev/null c 3 2 \
&& chmod 666 /dev/null