Mainframe OS & emulator on Raspberry PI

Mainframes are a technical oddity: they seem legacy (most workloads in COBOL&FORTRAN; an interface that looks like it's still the 70s), arcane(JCL job scheduling, mainframe terminology), yet extremely powerful(very high concurrency, great security, extreme availability) and critical(government, banking).

Getting some basic experience requires either:

1. Access to a real one, e.g. via IBM Cloud

2. Paying some serious money for a license to run zOS on a homelab machine(x86)

3. Running on top of a hardware emulator(Hercules), an ancestor of zOS that has an almost identical look and feel(MVS).

For technical curiosity only, I found option 3 the most appealing and more specifically: https://www.prince-webdesign.nl/tk5

The package contains both the emulator and MVS, so once you set it up, you only need to install a 3270 terminal client(several options available for Linux, Mac, Windows).

Initially, I set everything up on an Ubuntu VM, later on Ubuntu Docker and finally on a Raspberry PI 5.

I found hosting on a dedicated Raspberry PI the most rewarding experience, as it feels like having a tiny mainframe in your home lab, with the caveat that for security reasons, it's best to host it on its dedicated network, without direct access to the internet.

Hope you find this useful. (the 70s are back!)

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