[skissane]

> BSD, IllumninOS, IBM z/OS did it first in supporting Linux APIs in some form, either by syscall remapping or VMs.

z/OS has only gained support for running Linux binaries quite recently, in z/OS 2.4 (released September 2019), which supports running z/Linux Docker containers (zCX). Prior to that, z/OS had no built-in support for running Linux binaries in any form. Microsoft released WSL1 in August 2016. So z/OS got this feature 3 years after Windows did.

You might be thinking of z/VM or PR/SM, both of which support running z/Linux virtual machines (but neither of which is z/OS); or of z/OS Unix System Services, which offers some degree of source compatibility with Linux (through its implementation of the UNIX 95 standard), but doesn't have any Linux binary compatibility.

[pjmlp]

Yeah I guess those ones, as I remember IBM mainframes have had support for Aix/Linux guests for a while now.

Thanks for the correction.

[skissane]

> as I remember IBM mainframes have had support for Aix/Linux guests for a while now

IBM VM has supported Linux guests ever since Linux was first ported to IBM mainframes, circa 1999-2000. Indeed, it is quite likely the initial port was done using VM.

IBM offered two versions of AIX on mainframes, AIX/370 in 1998 and AIX/ESA in 1991. However, how much code did these have in common with AIX on RS/6000? In the later case, very little – AIX/ESA is actually a port of the Mach kernel based OSF/1 to IBM mainframes, with little or no code shared with RS/6000 AIX (which contemporary AIX descends from). It actually had more in common with Digital/Compaq/HP's discontinued Tru64 UNIX (which is another OSF/1 derivative) than with AIX on RT-PC / POWER. I get the impression that AIX/370 had little or no code in common with RS/6000 AIX either – it was developed by Locus Computer Corporation – but I don't know enough about it to be sure about that. Neither AIX/370 or AIX/ESA ever saw any great adoption – both were discontinued in the 1990s, they were replaced by MVS OpenEdition (later OS/390 OpenEdition, and now z/OS Unix System Services) and also later on also by Linux.

[skissane]

> AIX/370 in 1998

Typo: 1989 not 1998

[pjmlp]

Thanks once more. :)