In the previous DBAOTM post I have introduced you to the z/OS operating system, the flagship operating system for the mainframe. In this post I will introduce you into the Unix side that z/OS has been equipped with over the past two decades. Since the 1990s IBM has added Unix functionality to z/OS. The first extension was z/OS Unix System Services – z/OS Unix in short - and recently we IBM have added z/OS Container Extensions. z/OS Unix The Unix part of z/OS is a runtime environment that is an integral part of the z/OS operating system. z/OS Unix is fully Unix (Posix) compliant. z/OS Unix provides an interactive command interface that is called a shell in Unix terminology. IBM has developed this part in the 1990s to make it easier to port applications from other platforms to z/OS. Many off-the-self and open source middleware and application packages that are available on z/OS make use of z/OS Unix. Examples are IBM’s own WebSphere Application Server and IBM Integration Bus, the banking product BASE24-eps from ACI, and open source tools like PHP and Git. z/OS Unix has regular files the same as other Unix systems. In the z/OS Unix shell you can use normal Unix commands like ls, cd, more and many more of the standard Unix commands. You can set up a telnet or SSH session with z/OS Unix and do many more things you can also do with other Unix environments. z/OS Container Extensions A very recent development on z/OS (it came with z/OS 2.4, end 2019) is the possibility to run Linux Docker Containers on z/OS. Docker containers are a hardware independent and lightweight manner to run many applications in a virtualized configuration. The Docker technology has been available on x86 platforms for a long time. With Docker containers you get a virtualization solution that does not need a complete virtual machine with an operating system running in it for every application. Instead your application is running in a small container that provides only a limited set of virtualization facilities. Just the things that the application needs. You can run many Docker containers – so applications – on a single real operating system image. The interesting thing is that in a conceptual way Docker is a quite like z/OS as we have seen it in section Address Spaces are processes. On a z/OS operating system you can run many applications in “Address Spaces”. With Docker you run many container processes on a single real operating system image. I will talk a bit more about Docker in section Linux in z/OS Container Extensions. z/OS Address Spaces versus Docker containers All Unix variants A small elaboration, as you may already get confused with the Unix on the mainframe. I mentioned Linux for the mainframe, now I talk about z/OS Unix and Linux in Containers. It is important to understand the difference between z/OS Unix, z/OS Container Extensions and Linux for Z. z/OS Unix and z/OS Container Extensions are an integral…