[Gllug] Changing permissions on removable media

Nix nix at esperi.org.uk
Sun Mar 23 22:14:15 UTC 2008


On 23 Mar 2008, John G. Walker outgrape:
> This system has worked when the drive was connected to the Windows PC
> and when it was connected to the SuSE 10.1 PC. However, now it's
> connected to the SuSE 10.2 PC the file permissions for the drive seem
> to be screwed up.
>
> No problem, I thought. I'll just manually adjust them via root. But It
> tells me that the operation is not permitted.
>
> Why not? My tiny brain was under the impression that root could do
> anything. And, anyway, how do I sort out the permissions on a piece of
> removable media?

Among the things root cannot do:

 - adjust the permissions of an immutable inode
 - adjust the permissions on many filesystems that do not support
   such things; many of them set permissions via a mount option
   instead

(On some other filesystems, permission alterations seem to work, but
never go to persistent storage and vanish at some later point when the
inode gets dropped from the page cache. Generally this sort of behaviour
is considered a bug, but I know that VFAT for one used to work this
way.)

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