"mount --bind" with user/group/mode definition?

"mount --bind" with user/group/mode definition?

[Ph. Marek]

Hello everybody,

is there some way to duplicate a directory somewhere else (like 
with "mount --bind"), but having different owner/group/mode bits?

I'd like to mount a directory I have no control over (think NFS, or 
floppy, ...) with clearly defined rights - like root:<some group>, mode 0550 
for all directories, and 0440 for all files.
(Here I want to have full *read* control, regardless of the original 
permissions).
[ I know that this special case can be (mostly) done by a read-only binding
  mount; the part that is missing is eg. files with a different owner being
  0700. ]

I know that something like this is possible for eg. VFAT, which has no right 
descriptors for itself; but I'd need that for arbitrary directory trees, who 
themselves *have* permissions set.


Is there some way to achieve that?


Regards,

Phil

Re: "mount --bind" with user/group/mode definition?

[Kyle Moffett]

On Oct 11, 2007, at 04:35:37, Ph. Marek wrote:
> is there some way to duplicate a directory somewhere else (like  
> with "mount --bind"), but having different owner/group/mode bits?
>
> I'd like to mount a directory I have no control over (think NFS, or  
> floppy, ...) with clearly defined rights - like root:<some group>,  
> mode 0550 for all directories, and 0440 for all files. (Here I want  
> to have full *read* control, regardless of the original permissions).
> [ I know that this special case can be (mostly) done by a read-only  
> binding mount; the part that is missing is eg. files with a  
> different owner being 0700. ]
>
> I know that something like this is possible for eg. VFAT, which has  
> no right descriptors for itself; but I'd need that for arbitrary  
> directory trees, who  themselves *have* permissions set.
>
> Is there some way to achieve that?

Not at the moment, unfortunately.  I suspect that with the recent  
developments in user container support and/or overlay mounting it  
will become possible to either write a UID/GID-translation overlay  
filesystem or grant cross-UID-container keys to achieve what you  
want.  On the other hand that probably won't fully happen for up to a  
year or so.

Cheers,
Kyle Moffett