Very useful for admins with little time to recompile software. Solaris Freeware SunSITE Home Page Provide free software and tools. It has a lot of mirror sites and not only for the products by Sun Microsystems. This is what they say in the cover page. You can find out what GNU is for a UNIX systema diministrator.
Programming is the basic requirement for UNIX system adminstrator.
You can use any UNIX shell, but I prefer Perl. This camel is very powerful. If you really want to become a UNIX network system administrator, you must know how the email works. My experience is that almost 30 persent of the questions from users is about the emai. I recommend you spend some time on the sendmail.