Fix 'writes' lack of permission to write to terminal in Debian
In Debian, the ‘write’ program does not seem to have the right permissions to be able to tty’s unless it is root.
The problem is that the program does not run with the correct permissions. The user does not have access to write to tty’s, but the ’tty’ group does.
To get write to have access to write to ttys’, issue the following two commands…
sudo chgrp tty /usr/bin/write
sudo chmod g+s /usr/bin/write
This makes “write” run as the tty group. The first like makes tty the group owner of the executable, and the second like makes the process run with tty group permissions when run.