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Let's make it official

Given that the last post on this blog was a bit more than 2 years ago it should not come as a surprise to anyone; I feel like I have sufficiently scratched the mainframe itch and have moved on to other projects. I have spent the last few months getting all my mainframe equipment into the hands of the next-generation of hobbyists and since a week or so I am now officially sans mainframe. This also means it feels a bit silly to operate a blog or an internet persona around supposedly doing things with mainframes, when I do not own one or participate in projects around them.  Enjoy some parting images from the move.         Image 1: Getting a mainframe down a ramp requires a lot of friends          Image 2: Mainframe loaded and ready to move to its new home I have been thinking about possible other names to rebrand my shenanigans but nothing concrete yet. The current blog will remain here hosted on, for how long I guess time will tell :-). Thanks for reading and following alon
Recent posts

zBC12, the new family member

Yesterday after more than a year's delay my zBC12 mainframe finally booted up. This is a machine that was donated to me in hopes to advance the hobbyist community, which I am eternally grateful for. Image 1: Athena, the zBC12 that just now got online Then what is the main selling point of the zBC12 versus the z114? You might recall my article  System z on contemporary zLinux  where I explained that running modern Linux on a z114 is hard. This is the main selling point for me to upgrade - being able to run things like more modern Linuxes than z114. While the latest OSes in zLinux, z/VM, and z/OS require z13 or newer - a zBC12 still allows me to run a few releases newer software. Image 2: The operator himself in the picture with Athena Perhaps one of the bigger deals that is very welcome is the support for OSA-Express5S. This means that while previously you needed both PCIe and I/O bays in order to have both effective higher speed connectivity like 8G FC or 10 GB Ethernet as well as

The curious case of the missing return packet

 In this post I want to dig deeper into a phenomenon that I spent a few day debugging with friends. It will be a story of a behavior that seems illogical at first glance, broken even, but will seem feasible in the end. Let's begin! Things you will need: The scenario requires one host and one switch minimum*. In our example we will use two Linux hosts, an Arista DCS-7050S switch, and an Arista DCS-7050QX switch. The second switch and host is not strictly needed, but it makes the scenario more realistic and is how we found this issue. The story begins with you and a couple of friends are building an internet exchange (IX) for education and for fun. The simplest IX is just a simple switch - yes even an unmanaged thing you can pick up for $10 would work theoretically. The switch has one purpose: connect different actors together so they can route traffic between each other. See diagram 1. Diagram 1: Your typical IX network. It's just a switch. You have your IX switch and you have y

Updating a Mainframe

I have done systems administration for as long as I remember, and while I have set up countless of services and servers - I have quite limited experience working with the full life-cycle of truly enterprise software. Therefor, I thought it would be interesting to understand more on how one would plan for and execute updates on an IBM Z Series mainframe.


I have to make a post mentioning the last couple of months, anything else would just be weird I feel. I hope you all are doing as well as can be in these unpredictable times. I know I have been personally affected by this pandemic in multiple ways yet I feel fortunate - things could have been so much worse.  While I am one of the lucky people who work in a job that lends itself reasonably well to work from home, it took some time to get used to which had me focus more time and effort on things like home improvements and new daily routines to help me adjust to this new way of living. Thankfully I was not alone in this journey and I am thankful to all my friends, family, and of course my partner for being there for me. We all need to take care of each other. The last couple of weeks I have resumed my work on mainframe related projects and I have a series of blog posts that I wish to publish coming up. Some of these topics are going to be deep-waters territory for me, but the community ha

Hacking update

Wow, time flies. In the past months I've been working on a handful of projects related to the mainframe, but nothing that is really finished - so I thought I would summarize some work I've been doing instead.

The fake FICON board - Fejkon

The latest project I've been working on is a custom card that will allow me to interface any mainframe using the FICON protocol. I have a lot of ideas on how this could help a lot of hobbyists out there, and possibly folks doing development for mainframes as well. For my own purposes, it would allow me to not be reliant on my (still broken) DS6800 array. DE5-Net card running fejkon