I'm guessing you're asking about Linux sysadmin and not Windows sysadmin, but correct me if I'm wrong.
What sort of Linux experience do you have already? Are you looking to spend money on resources or free stuff only? Also, are you looking for generic "sysadmin" concepts, or for how to implement on a particular operating system like CentOS or Ubuntu?
Someone else on HackerNews just open sourced his tutorials: https://github.com/snori74/ebook1. They're written for someone new to Linux but has some Windows background.
I think it starts with you telling us which OS. While the basic concepts are the same regardless of the OS, there are targeted sites/books/videos for each that can shorten your specific learning curve.
What sort of Linux experience do you have already? Are you looking to spend money on resources or free stuff only? Also, are you looking for generic "sysadmin" concepts, or for how to implement on a particular operating system like CentOS or Ubuntu?
Someone else on HackerNews just open sourced his tutorials: https://github.com/snori74/ebook1. They're written for someone new to Linux but has some Windows background.