Linux + z/VM = z/Linux

Let's Demystify

z/Linux aka "Linux on Z" is a Linux compiled for IBM architecture s/390 machine.

The most common distributions RedHat and SUSE, and now mainly RedHat since its acquisition in 2018 by IBM.

One of the interesting points of the solution for Mainframe IBM sites is to allow them to "test" zLinux on their existing infrastructure without hardware investment, by creating a virtual environment via the z/VM (formerly "VM/CMS") hypervisor: a z/VM LPAR, then virtual machines.
These virtual machines will "boot" Linux (on z/VM side, it's an IPL on DASDs having Kernel Linux): Et voila!

One could functionally compare z/VM to VMWare, but the comparison stops there.

Of course, to go further, it needs to invest in Integrated Facility for Linux (IFL) specialized processors and machines dedicated to Linux: LinuxONE.

For the system administrator, the main differences between Linux x86 and s/390x are:

  • device drivers : disk, network
  • Boot manager : grub (x86) vs zipl (s390x)

For "Bit & Byte" developers, the only difference is:

  • CPU endianness : little-endian (x86) vs big-endian (s390x).

Once these differences are exposed, Linux s/390x is absolutely identical to Linux x86!

You will find many introductions on Linux on Z, its Use cases and Business cases, as well as articles discussing the pros and cons of the Linux on Z strategy.
We will therefore leave it to the reader to form his own opinion.

For the anecdote, Henri Henault already wrote in 2001 this article sur Linux S/390.

Our added value

Implementing Linux on Z within an IS raises a delicate point:

What strategy should be adopted so that the implementation of Linux on Z runs smoothly?
in particular how to establish cooperation between Open and Mainframe teams? two worlds historically and culturally closed to each other.

Among the key questions:

  • How to introduce to Open and Mainframe teams their participation?
  • Which RACI to set that will cover Build, Run & Maintain, support for both components:
          - z/VM Hypervisor
          -Linux OS
  • What skills and training will be needed?
  • What work will be necessary to adapt the existing installation automation (portals, technical repositories, Jenkins, VMWare API, ansible, kickstart, etc ...) to z/VM z/Linux?
  • and many more...

From its experience on Linux on Z implementation projects at big shops, HH&S can provide advice and expertise on these topics.

PS: à HH&S, we love VM, we love Unix/Linux!

Call us to talk about your z/Linux project!