1) Integrity. No skill, education, or experience is a substitute for integrity. Everything else can be corrected, but if you have an integrity problem, then how can I know that you aren't lying about being reformed?
2) Experience with A) Linux, B) Apache, C) MySQL, D) PHP, and E) VMware.
2 a, b, c & d) Look at Netcraft. Most servers on the Internet are running open source software. After all, you can run
ASP.NET on:
Windows with IIS
or PHP on:
Windows with IIS, Apache, Lighttpd, or Nginx
Mac with Apache, Lighttpd, or Nginx
Linux with Apache, Lighttpd, or Nginx
FreeBSD with Apache, Lighttpd, or Nginx
OpenBSD with Apache, Lighttpd, or Nginx
NetBSD with Apache, Lighttpd, or Nginx
Solaris with Apache, Lighttpd, or Nginx
AIX with Apache, Lighttpd, or Nginx
HP-UX with Apache, Lighttpd, or Nginx
You get the idea...
E) Virtualization is the future. I'm tired of typing, so you'll just have to trust me on that.