"Permissions Denied" error as root: SOLVED

[R. G. Newbury]

R. G. Newbury wrote:
To recap, attempting to run a script, as root, with permissions 755 
produced a 'Permissions denied' error.

The problem was that the partition was mounted with 'users,defaults' 
options, and 'users' implies 'noexec' and overrides 'defaults' (which 
implies 'exec'),

Changing the line in fstab to 'defaults' and quick 'umount' and 'mount' 
fixed the problem.

Weird bit is that I was logged in as root..WHICH WAS MISLEADING. When 
'nonexec' is set, ALL users are denied execution privileges. (This is 
most useful for security purposes in denying the use of programs on for 
example a USB stick from compromising the system.

So, besides checking the permissions on a file, and the parent 
directories, you have to check how the partition was mounted.
This will catch you when you are playing with something on a 'spare' 
partition.
Or when you change the fstab without realizing the implications!

Thanks to all for the pointers, which gave the solution.

Geoff