Dillon studied electronic engineering and computer science at the University of California, Berkeley, where he first became involved with BSD in 1985. He also became known for his Amiga programming and his work on the Linux kernel. He founded and worked at BEST Internet from 1994 until 1997, contributing to FreeBSD in that time.
In 1997, Dillon gained commit access to the FreeBSD code and rewrote the virtual memory subsystem, amongst other work.
Concerned with problems he saw in the direction FreeBSD 5.x was going, he started DragonFlyBSD in 2003.