Re: Wishlist Item :: One Subvol in Multiple Places

[Austin S Hemmelgarn]

On 2014-10-14 18:25, Robert White wrote:

I've got no idea if this is possible given the current storage layout,
but it would be Really Nice™ if there were a way to have a single
subvolume exist in more than one place in hirearchy. I know this can be
faked via mount tricks (bind or use of subvol=), but having it be a real
thing would be preferable.

For example, if I have two or more distributions on a computer or want
to switch between 32bit and 64bit environments frequently, but I want to
use the same /home (which is its own subvolume anyway) it would be nice
if the native layout could be permuted such that /__System_32/home and
/__System_64/home were the actual same subvolume.

The mechanism, were it possible, would be something like "btrfs
subvolume link /existing/path /new/path" (or "bind" instead of "link")

I've got no idea if the directory structure would allow for this, but if
it would it would simplify several things (for me anyway) if the file
system layout represented the runtime layout.

This probably won't be implemented, for the same reason that most modern unix systems disallow hardlinks to directories; namely, it results in ambiguity regarding resolution of the .. directory entry. The better solution would be to put /home in a separate top-level sub-volume, and then mount that in each location.

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