Memory disk "a la mfsroot"?

[RW]

On Thu, 11 Feb 2010 15:12:22 +0000
Matthew Seaman <m.seaman at infracaninophile.co.uk> wrote:

> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> On 11/02/2010 14:53, Pierre-Luc Drouin wrote:
> 
> > I would like to know if there is a mount command that allows to
> > create a memory disk that can be initialized from a file. What I am
> > looking for is something like mount_mfs -F, but that does not
> > modify the actual file. I know what I could easily to this by
> > copying the content of the file to the memory disk, but I am
> > looking for a solution that can be configured via fstab.
> 
> Yes.  See mdconfig(8) -- there are examples in there of exactly what
> you want to do.

I don't think covers what he is asking for. I think you would need a
union filsystem that overlays a swap-backed filesystem on top of a
file-backed filesystem - if that's possible.