Re: Transparent mounts

Jens Axboe (axboe@image.dk)
Thu, 18 Nov 1999 02:09:04 +0100

On Wed, Nov 17 1999, Riley Williams wrote:
> Basically, one facility I could use is that of being able to mount two
> or more partitions on top of each other and have all the files from
> all of the partitions available for reading. This is what I call a
> transparent mount.
>
> 1. The partition(s) being mounted over must already be mounted
> read-only. There is therefore no problem with where to put
> any newly created files on such a system since such can't be
> created in the first place.

BSD does it differently. All layers are read only except
the top one. If a file from a lower layer is opened for writes,
it is copied to the top layer first.

> 2. There must not be any name clashes between the contents of
> the partition(s) already mounted at that point and that of
> the root directory of the partition being transparently
> mounted on top of it.

Or just decide to hide duplicates on your own, say the top
layer will always show up.

-- 
*  Jens Axboe <axboe@image.dk>
*  Linux CD-ROM Maintainer
*  http://www.kernel.dk


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