Re: [gentoo-user] how to access mounted dir with non-root?

[Neil Bothwick <neil@digimed.co.uk>]

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On Fri, 12 Aug 2005 21:45:44 +0200, Holly Bostick wrote:

> > Don't you mean umask=0? umask inverts the bits, so 777 gives
> > --------- to all files.
> > 
> > 
> 
> I'm currently in the middle of an 'argument' with someone else about
> this, so explain, please.
> 
> If umask masks bits off of the 'default' permissions, then what is the
> point of umask=000?

To give rwxrwxrwx, which is fine for a FAT filesystem, and certainly
better than ---------

> It seems that it would leave the permissions as the
> default, which appear to be 755 (is there a creation mask of 022
> somewhere in the 'default' settings?

And there's the rub. Setting permissions to 755 only gives write access
to the owner, which is root when mounting at bootup. The other way of
dealing with this with FAT filesystems is to use the uid/gid options to
set yourself as the user, but that only works on a single user system.

> The other person says that umask=000 removes all restrictions and gives
>  all permissions to everybody, but I just don't understand how this
> could be, unless the specific file/mount point was already set that way
> (no file creation mask, so the files are 'created' with the default
> 777/666, or inherited the permission structure of the parent).

The mount point is irrelevant, what counts is the permissions on the
mounted filesystem, not the parent of the mount point. Once you mount
something on it, it takes on the permissions of the mounted device.

# ls -ld t
drwxr-xr-x  2 root root 6 Apr 21 13:34 t

# mount /dev/sdd1 t -o umask=0

# ls -ld t
drwxrwxrwx  7 root root 16384 Jan  1  1970 t

See, the 755 changes to the 777 specified in the mount
options. /dev/sdd1 is a FAT16 formatted flash disk.
    

-- 
Neil Bothwick

"We demand rigidly defined areas of doubt and uncertainty!"

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