SmartOS is a [ree and open-source software SVR4 hypervisor based on the UNIX operating system that combines OpenSolaris technology with Linux's KVM virtualization. Its core kernel contributed to the illumos project. It features several technologies: Crossbow, DTrace, KVM, ZFS, and Zones. Unlike other illumos distributions, SmartOS employs NetBSD pkgsrc package management. SmartOS is designed to be particularly suitable for building clouds and generating appliances. It is developed for and by Joyent, but is open-source and free for anyone to use.