I am now successfully runninf 4 UML instances in a virtual network with COW files. It is a very good feature as my original filesystem remains intact and only COW files are written into. And still I can access all data on my original root_fs without wasting any disk space (that would have required if I would have created 4 copies of the original root_fs).

On 6/5/06, Anthony Brock <Anthony.Brock@oregonstate.edu> wrote:
> -----Original Message-----
> On Tuesday 30 May 2006 20:07, Brock, Anthony - NET wrote:
> > You need to create a separate COW file (probably based of the same
> > original image) for each instance. Your customizations will then be
> > written to the COW file while preserving the base image intact. This
> > will also bypass the file locking issue.
> To be clear: this is not a "disadvantage" caused by file locking.
> Using the
> same image will cause problems, because each kernel doesn't know
> about the
> other and concurrent changes will cause incoherencies, and the locking is
> there to prevent you from shooting yourself in the foot.

Correct. About the only time you would want simultaneous access from
multiple OS's to the same file system is either via a network-based file
system (such as NFS) or via a "clustered" file system (such as OCFS or GFS),
both of which are designed to prevent file system corruption if properly

I didn't mean to imply that the file-locking was a mistake or something
"bad" in this situation.