Can I run Linux or FreeBSD as a in an LDoms environment?
Some Linux distributions (e.g. Ubuntu, Wind River, Gentoo, etc.) can run on CoolThreads servers (Niagara, UltraSPARC T1) natively, but not as a guest OS in a strict sense. Because the guest OS has to be modified by the nature of paravirtualization, namely to add virtual devices support, which was integrated into Solaris 10 11/06 (update 3).
However, you should be able to run Ubuntu on a domain that does not need any virtual devices. So you can try to create a new domain and assign a PCI bus to that domain. Then you need to have a disk and network card connected to this PCI bus and you can use the new domain as a regular sun4v system and install Ubuntu from the network. The limitation with such a configuration is that you can not use virtual devices (vdisk, vnet) on the domain running Linux, and some LDoms feature will not work (like dynamic reconfiguration of vCPU).
Also for the current Niagara servers, you can only create one domain running Linux because there is one PCI bus available to create a new domain, while the other is occupied by the control domain running Solaris. Once the community brings the virtual devices functionality to Linux, FreeBSD, etc., then they are run as guests in an LDoms environment. Stay tuned.
Welcome your feedback on the use cases of Linux and FreeBSD leveraging LDoms on Niagara servers.