Technote (FAQ)
 
Question
I have a modem attached to tty0 and am trying to run this command:
# cu -ml tty0

Which results in this error:
0835-028 device locked

How can I resolve this issue?
 
Answer
Check the permissions of the /var/locks file.

# ls -ld /var/locks
drwxrwxrwt 3 root system 256 Feb 23 20:05 /var/locks

The default permission and ownership should look like above.

To set the permissions as above (rwxrwxrwt ), use this command:
# chmod 1777 /var/locks