FreeBSD
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FreeBSD is a free, Unix-like operating system derived from AT&T Unix via the Berkeley Software Distribution (BSD) branch through the 386BSD and 4.4BSD operating systems. It is not a clone of UNIX, however it works much in the same way as UNIX, featuring UNIX-compliant internals and system API's. FreeBSD is held in generally high regard and is often characterized as dependable and sturdy.

