Device access (cont)

Device access is controlled by standard Linux file permissions.

Ability to write to terminals requires group 'tty'
         $ ls -la /dev/tty1
         crw--w----  1 bree   tty        4,   1 Apr 18 14:00 /dev/tty1
         
         $ grep tty /etc/group
         tty:x:5:
         
         $ ls -la /usr/bin/write
         -rwxr-sr-x  1 root   tty          7540 Jul  4  2002 write