AIX
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Stands for: Advanced Interactive eXecutive, IBM's Unix, 1986 to the present
Advanced Interactive eXecutive, IBM's proprietary Unix, first released in February 1986 for the RT PC and still current on Power servers; System V with 4.3BSD extensions, and the first operating system with a journaling file system.
AIX is the vendor Unix that did not end. IBM has developed and sold it since 1986, the name stands for Advanced Interactive eXecutive, and the current versions run IBM's Power ISA servers and workstations alongside IBM i and Linux; the latest release at the time of reading is 7.3 TL4 of December 2025. It was originally released for the IBM RT PC RISC workstation in 1986 and has since run the RS/6000, Power and PowerPC systems, System i, System/370 mainframes, PS/2 personal computers and the Apple Network Server. It is based on Unix System V with 4.3BSD-compatible extensions and is certified to the UNIX 03 and UNIX V7 specifications of the Single UNIX Specification, from AIX 5.3 and 7.2 TL5 respectively; older versions were certified to UNIX 95 and 98. AIX was the first operating system to implement a journaling file system, and IBM has continuously added processor, disk and network virtualisation, dynamic hardware allocation including fractional processor units, and reliability engineering derived from its mainframes. The kernel is monolithic with dynamically loadable modules; the default shell is ksh88.
Background. IBM's involvement with Unix began in 1979, when it helped Bell Labs port Unix to the System/370 as a build host for the 5ESS switch's software; Unix itself had begun at Bell Labs in the early 1970s on DEC minicomputers and had been ported to the S/370 at Princeton by 1976, a port that became Amdahl's UTS. AIX arrived in February 1986 for the IBM RT PC, IBM's RISC workstation, and has since supported the RS/6000 series and the Power and PowerPC systems that followed, IBM System i, System/370 and ESA/390 mainframes, PS/2 personal computers, the Apple Network Server and, for a time, Itanium. Today it is supported on IBM Power Systems alongside IBM i and Linux.
What kind of Unix. AIX is based on Unix System V with 4.3BSD-compatible extensions, with a POSIX and Single UNIX Specification userland. It is certified to UNIX 03 from AIX 5.3 and to UNIX V7 from AIX 7.2 TL5; older versions were certified to UNIX 95 and UNIX 98. The kernel is monolithic with dynamically loadable modules; the default interface is the Korn shell, ksh88, with the Common Desktop Environment and optionally Plasma or GNOME on the desktop. It is written in C, closed source, formerly source-available.
Firsts and engineering. AIX was the first operating system to implement a journaling file system. IBM has continuously enhanced it with processor, disk and network virtualisation, dynamic hardware resource allocation including fractional processor units, and reliability engineering concepts derived from its mainframe designs, which is the context in which most administrators meet those features. The current release line is 7.3, with technology level 4 released in December 2025, and the working state is current.
Why it belongs beside the others. HP-UX reached its end of support on 31 December 2025, Solaris became closed again after 2010, IRIX ended in 2006; AIX is the one of the four vendor Unixes still being released on a vendor's own processor architecture. For a network engineer the relevant facts are that the host runs System V tooling with IBM's own additions, that its network stack is configured through IBM's utilities rather than Linux's, and that the machines it runs on sit at the centre of the estates, banks, airlines, insurers, where the oldest and most critical applications live. The IBM record on the industry timeline carries the company.
Also known as: ibm aix, aix 7.3, power aix, rs/6000