Folders must be made executable?

[David Miller]

Kent Frazier wrote:
> I recently reinstalled Ubuntu from the Hoary Array 2 disc and almost
> everything worked fine.  I ran into a rather strange issue with some
> of the subdirectories in my home directory.  When I would open them in
> nautilus, I could see the contents, but the application specific icons
> were replaced with the generic gnome foot and I couldn't do anything
> to any of the files, including open them.  When I try to list them
> from the command line with ls (as normal user) it tells me permission
> is denied.  By experimenting, I found I could make them work properly
> by setting the executable bit, which was off for those that were
> misbehaving.
> 
> Is this buggy behavior, or is this the way this is supposed to work? 
> I had never run across this before, but that may have just been a
> coincidence.

That's the way it's supposed to work.  On a directory, the executable 
bit actually means "permission to enter this directory".  If it's 
readable, but not executable, then you can see what files are in it, but 
you can't enter the directory, and hence can't open the files in it.

Conversely, it's possible to make a "blind" directory by setting it as 
executable, but not readable.  Now you can enter the directory, but you 
can't see what's in it.  But if you happen to know one of the filenames, 
you can get to it.  This is commonly used on ftp servers to provide a 
temporary place for people to put files to trade with other folks... 
make it readable and writable, but not executable.  They give the 
filename to the person they want to send it to, and they can get it. 
But you have no way to tell it's there if you didn't already know the 
filename.

-- 
Dave Miller                                   http://www.justdave.net/
System Administrator, Mozilla Foundation       http://www.mozilla.org/
Project Leader, Bugzilla Bug Tracking System  http://www.bugzilla.org/