Or an Illumos Zone.. Illumos being a fork of OpenSolaris.
Even better, you can run Linux inside an Zone on SmartOS, an Illumos distribution, via system call translation..
And Smartdatacenter+ sdc-docker = SmartOS based IaaS solution with docker support..
Smartdatacenter and SmartOS are made by Joyent, everything is opensource.
That's what they use to power their public cloud..
Truly an hidden gem, as other Joyent opensource stuff like manta..