The part that is specific to the mainframe is the handling of mainframe-specific devices, the dependence of the mainframe Linux on the network (working at the console of a mainframe Linux system without a network is exactly like working on a printing TTY -- it's possible, but if you've never done it before, it's a steep learning curve) and the process of managing startup/shutdown in the LPAR and VM environment. These topics are covered in some detail in the IBM Redbooks. A listing of Linux-specific Redbooks is maintained on LinuxVM.org and are well worth downloading and reading the PDF versions.
The other thing you should become familiar with is the concept behind virtual machines. The z/VM Getting Started with z/VM for Linux manual (in the z/VM 5.1 documentation set) that is in the z/VM 5.1 documentation set is a great start for that, in an context of how to set up z/VM to support Linux. Both the Redbooks and the IBM manual I mentioned are fairly thick -- print them after hours if you use a work printer. 8-)
You should also be aware of the Linux-390 mailing list at vm.marist.edu. This is the primary resource for
learning about Linux on the mainframe -- most of the people involved in the development and support
(from both IBM and other organizations) hang out there. It's fairly friendly (compared to other
sources of Linux info) to beginner questions, and you get the advantage of answers direct from the
people who care about the topic. You can subscribe to linux-390 by sending an e-mail with the words
yourfirstname yourlastname in the body of the message.
Last, there are excellent sessions at the major user conferences like WAAV and at the IBM z/Expo on Linux on the mainframe. I and smy colleagues teach several of them, and there is a large IBM presence in both cases. Both are great opportunities to hang out with the developers and get free input on how to do something in your environment. I know I go through a lot of pencil and paper at both conferences talking with people about problems and how to approach them -- it's well worth your time and travel budget to attend.
This was first published in December 2005