FreeBSD

NetBSD is a free, fast, secure, and highly portable Unix-like Open Source operating system. It is available for a wide range of platforms, from large-scale servers and powerful desktop systems to handheld and embedded devices. NetBSD was originally released in 1993. Over time, its code has found its way into many surprising environments, on the basis of a long history of quality, cleanliness, and stability. The NetBSD code was originally derived from 4.4BSD Lite2 from the University of California, Berkeley. NetBSD is an entirely free and open-source UNIX-like operating system developed by an international community. It isn't a "distribution" or variant but has evolved over several decades to be a complete and unique operating system in the BSD family. NetBSD users enjoy a simple, well-documented, and fully integrated UNIX-like system that feels minimal, and in many ways traditional, while including many modern and interesting features, and support for recent hardware.

The open-source enterprise server OS with just the features you need. ZFS, OmniOS' native file system, combines a volume manager and file system with strong data-integrity protection. Easily share volumes via iSCSI, CIFS, and NFS. Run lightweight OmniOS or Linux virtual machines in containers without the overhead of a traditional hypervisor and with full resource control. OmniOS also provides full hardware virtualization via bhyve and KVM for running guests such as Microsoft Windows, FreeBSD, and many others. Virtualize your network infrastructure through Crossbow virtual interfaces and switches and even allocate dedicated resources for specific services. DTrace provides a comprehensive dynamic tracing framework to aid troubleshooting across the whole software stack. Always available, instrument anything on demand. OmniOS is open-source, self-hosting, and maintained on GitHub. All development is done out in the open with pull requests and anyone can grab the source and build OmniOS.