can't open file for writing

I get the error "can't open file for writing" when I try to change a file on a remaster of Knoppix 3.4 under the root user. Is there a way to prevent this error from occuring? It happens when I try to edit a file with vi editor. I understand the fact that this error occurs because i'm attempting to modify a file that has read-only permissions. I would like to know if there is anything I can do to knoppix to avoid this error after I make a remaster?
Thanks in Advance.

I just noticed that I can edit the file if it is located in the /home/knoppix directory. Is there a way set the permissions on the usr/local/etc/ to be similar to /home directory?