FreeBSD

FreeBSD's distinguished roots derive from the BSD software releases from the Computer Systems Research Group at the University of California, Berkeley. Over twenty years of work have been put into enhancing FreeBSD, adding industry-leading scalability, network performance, management tools, file systems, and security features. As a result, FreeBSD may be found across the Internet, in the operating system of core router products, running root name servers, hosting major web sites, and as the foundation for widely used desktop operating systems. This is only possible because of the diverse and worldwide membership of the volunteer FreeBSD Project.

FreeBSD includes a number of great features:

• Firewalls: The base system includes IPFW and IPFilter, as well as a modified version of the popular pf with improved SMP performance. IPFW also includes the dummynet feature, allowing network administrators to simulate adverse network conditions, including latency, jitter, packet loss and limited bandwidth.
• Jails are a light-weight alternative to virtualization. Allowing processes to be restricted to a namespace with access only to the file systems and network addresses assigned to that namespace. Jails are also Hierarchical, allowing jails-within-jails.
• Linux emulation provides a system call translation layer that allows unmodified Linux binaries to be run on FreeBSD systems.
• DTrace provides a comprehensive framework for tracing and troubleshooting kernel and application performance issues while under live load.
• The Ports Collection is a set of more than 23,000 third party applications that can be easily installed and run on FreeBSD. The ports architecture also allows for easy customization of the compile time options of many of the applications.
• Network Virtualization: A container ("vimage") has been implemented, extending the FreeBSD kernel to maintain multiple independent instances of networking state. Vimage facilities can be used independently to create fully virtualized network topologies, and jail(8) can directly take advantage of a fully virtualized network stack.