can i setup 2 distros and run at the same time?
one is setup with redhat 9.0 to run my backup DNS server.
then i'd like to play with the other one, such as to try out all other distros.
Any other solution would be some form of system virtualization on top of Linode's virtualization which A) probably isn't possible, and B) is not a good idea anyway.
Is it possible to run a UML instance under UML?
Yes - but with a huge loss of performance. If you divide a UML instance into n sub-UML-instances, they not only have to share already-shared memory and processor power, they have to contend with one another for access to the UML I/O system, which then has to contend with other UML instances for access to the physical I/O system.
My guess: the load goes through the roof as processes block on disk activity.