Re: [PATCH 0/5] hybrid union filesystem prototype

[Jan Engelhardt]

On Thursday 2010-09-02 15:32, Neil Brown wrote:
>> 
>> Oh and I what I like to see is support for multiple readonly branches :)
>
>I think we very nearly have that, assuming I understand your requirement
>correctly.
>The lower filesystem can itself be an overlay, providing it is mounted
>read-only.
>
>So if /mnt/ro1 /mnt/ro2 /mnt/ro3 are all read-only branches then
>
> mount -o ro,lowerdir=/mnt/ro1,upperdir=/mnt/ro2 meaninglessstring /mnt/ov1
> mount -o ro,lowerdir=/mnt/ov1,upperdir=/mnt/ro3 meaninglessstring /mnt/ov2
> mount -o lowerdir=/mnt/ov2,upperdir=/mnt/rw ignoreme /mnt/overlay
>
>and /mnt/overlay will be the combination of 3 read-only filesystems and one
>writable one.
>(this doesn't work with the code as-is, but it is really just a few bug-fixes
>away).

There ought to be a reason that other implementations offer
doing multiple branches with a single vfsmount.
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