RFE: define device mapper CoWs

[foo ksbbk net]

I have a need to create a CoW (copy on write) on the root filesystem using
device mapper.  I do this manually after installation.  I'd like to see
this type of setup integrated into anaconda.

Although I have a specific need, I see many other possible applications
for CoWs that could use this type of feature.

o  Embedded flash devices with persistence that are easy to clear or reset.
o  Stateless installations where the CoW(s) are cleared at reboot or logout.
o  Testing installations where you may have several CoWs for for testing a
single base installation that are easy to cleared or reset.
o  Virtual installations that using the same root filesystem with
modifications by the different instances saved in different CoWs

I would like to see this handled in the anaconda partition setup where you
could define a partition as a CoW for one of the mounted filesystems.  Add
a kernel parameter similar to the “root=” except something like “cow=” to
define a root filesystem CoW and have a similar file as “fstab” except
maybe “cowtab” that defines non-root filesystem CoWs and where they are
located.

I think you may even have more ideas.  I think even the LiveCDs that use
device mapper with an in-memory CoW due to the read-only CD media would
benefit from anaconda support (add a kernel parameter something like
“cow=RAM=100mb”.

Am I crazy or alone in my needs?

Keith Adamson