Unix

I recommend NetBSD (http://www.netbsd.org/) because it has worked reliably and efficiently for me and my clients for a very long time.  I use it for hosting internet sites, and my clients use it for their internal network file server, internet firewall, DNS daemon, PostgreSQL database engine, VPN router, and so much more.  I greatly appreciate the excellent work that every contributor has made to NetBSD to make it such an excellent Operating System, which I expect will also continue to serve my technology needs so very well in the future -- thank you.