[linux-lvm] read-only media in a LVM?

[Joe Thornber]

On Mon, May 27, 2002 at 04:37:49PM -0700, Ami Fischman wrote:
> Hi there,
> I am wondering whether it is possible to have a read-only fs (CDROM, image,
> etc) as part of an LVM-managed volume.  I see references to COW
> (copy-on-write, I'm hoping :)) in the kernel drivers/md/ files, but it's not
> at all clear to me whether or not the current drivers can be used to
> implement a "translucent" or "inheriting" file system (one where a base fs
> is given, on r-o media, and changes to it get recorded on another device,
> presumabely a r-w fs).  Please let me know whether this is currently
> possible, being planned for the future, or if I'm making no sense above &
> you want me to clarify :).  For a not-quite-mature example of what I'm
> talking about, see translucency.sf.net.

In fact you can do this now if you use just device-mapper/dmsetup :)
It's just the LVM2 tools that don't support it yet.

- Joe