On a debian system, I'm logged in as root.
I cannot create any files in
I can create files in
/usr/share, etc, etc.
All these directories are owned by root and have permission 755.
The partition is not full.
touch /usr/bin/foo touch: cannot touch `/usr/bin/foo': Permission denied
(and the file does not already exist)
chmod fail on directories named "
bin" or "
sbin", but not on other directories.