IBM AIX

AIX
Company type	Proprietary software
Industry	Computer software
Founded	1986
Founder	IBM
Products	Unix operating system
Owner	IBM
Website	https://www.ibm.com/it-infrastructure/power/os/aix

AIX (pronounced ) represents a collection of proprietary Unix operating systems created and sold by IBM since 1986. The acronym stands for "Advanced Interactive eXecutive." Presently, it operates on Power ISA-based server and workstation devices, including IBM’s Power series.

Background

Initially launched for the IBM RT PC RISC workstation in 1986, AIX has been compatible with multiple hardware platforms. These include the IBM RS/6000 line, subsequent Power and PowerPC-driven machines, as well as the IBM System i, System/370 mainframes, PS/2 personal computers, and the Apple Network Server. Today, it runs on IBM Power Systems, coexisting with IBM i and Linux.

Built upon UNIX System V with extensions compatible with 4.3BSD, AIX complies with UNIX 03 and UNIX V7 standards from the Single UNIX Specification, starting with releases 5.3 and 7.2 TL5. Earlier editions adhered to UNIX 95 and UNIX 98 criteria.

AIX pioneered the use of a journaling file system. Over time, IBM has enriched the OS by integrating capabilities such as processor, disk, and network virtualization, dynamic allocation of hardware resources—including fractional CPU units—and reliability features derived from its mainframe innovations.

History

The Unix operating system originated in the early 1970s at AT&T’s Bell Labs on DEC minicomputers. By 1976, Unix had been ported to the S/370 as a guest OS running under VM/370 at Princeton University. This adaptation later evolved into Amdahl UTS, a competing mainframe Unix variant that gained prominence in the late 1980s.

IBM’s engagement with Unix started in 1979 when it helped Bell Labs port Unix to the S/370 platform to serve as a build environment for the 5ESS switch software, modifying TSS/370 Resident Supervisor to enable Unix support.

In 1984, IBM launched VM/IX for S/370, developed by Interactive Systems Corporation (ISC) using Unix System III technology. VM/IX was offered as a limited PRPQ product. By 1985, IBM replaced it with IBM IX/370—a fully supported system based on AT&T’s Unix System V developed by ISC—to compete with UTS.

ISC also created AIX for the IBM RT PC workstation introduced in January 1986. This version was based on UNIX System V Releases 1 and 2, incorporating source code from BSD UNIX. AIX Version 2 followed in 1987 for the RT PC and was also made available for IBM PC AT and XT/286 platforms.

In 1990, AIX Version 3 was released alongside the POWER-based IBM RS/6000 platform. Industry analysts recognized this as IBM’s formal commitment to Unix, positioning its proprietary AS/400 alongside the Unix-based RS/6000 to target midrange systems. AIX became the principal OS for RS/6000, which was later rebranded to IBM eServer pSeries, then IBM System p, and ultimately IBM Power Systems.

The introduction of AIX Version 4 occurred in 1994, bringing symmetric multiprocessing support. This version evolved throughout the decade until reaching version 4.3.3 in 1999. A customized variant of Version 4.1 served as the operating system for Apple Network Server hardware.

During the late 1990s, Project Monterey was initiated by IBM and Santa Cruz Operation with the goal of merging AIX and UnixWare into a unified multiplatform Unix tailored for Intel IA-64 architecture; however, due to limited market traction, this initiative concluded in 2002.

In 2003, SCO Group filed a lawsuit against IBM alleging unauthorized use of UNIX System V code within AIX; this legal matter was resolved in 2010 when a jury determined that Novell held ownership of Unix rights.

AIX 6 was unveiled in May 2007 and became available in November, introducing capabilities such as role-based access control, workload partitions, and Live Partition Mobility.

Following this, AIX 7.1 debuted in September 2010 featuring Cluster Aware AIX along with improved support for extensive memory configurations and real-time workloads.

IBM RT PC

The initial version of AIX, known as AIX/RT, was created for the IBM RT PC workstation through a collaboration between IBM and ISC, the latter having previously adapted UNIX System III for the IBM PC as PC/IX. The original AIX codebase contained approximately one million lines. Installation was provided via eight 1.2MB floppy disks. The RT utilized the IBM ROMP microprocessor, recognized as the first commercially available RISC processor, originating from IBM Research's development of the IBM 801.

A notable feature of the RT architecture was its microkernel, named Virtual Resource Manager (VRM), responsible for managing peripherals such as keyboard, mouse, display, disk drives, and network interfaces. Users could toggle between different operating systems using Alt-Tab, with each system gaining exclusive control over input/output devices during its active session. Besides AIX version 2, the PICK OS also employed this microkernel design.

The majority of the AIX v2 kernel was implemented in PL.8, which presented challenges when transitioning to AIX version 3. AIX v2 supported comprehensive TCP/IP networking alongside Systems Network Architecture (SNA), and included two network file systems: NFS, licensed from Sun Microsystems, and Distributed Services (DS), built on top of SNA and interoperable with IBM mainframe systems and midrange OS/400 platforms via IBM i. For graphical user interfaces, AIX v2 incorporated X10R3 initially, followed by X10R4 and X11 editions of the X Window System featuring the Athena widget toolkit. Compilers for both Fortran and C were made available.

IBM PS/2 series

AIX PS/2—also referred to as AIX/386—was developed by Locus Computing Corporation under contract with IBM. Its initial release occurred in October 1988, targeting IBM PS/2 personal computers equipped with Intel 386 processors and compatible CPUs.

Announced in September 1988 with a base price of $595, certain utilities such as UUCP were offered separately within an Extension package priced at $250. Text processing tools (nroff, troff) were sold in a $200 bundle; the TCP/IP protocol stack was available for $300. The X Window System package cost $195 and included the AIXwindows Desktop, which was based on IXI's X.desktop environment. Both C and FORTRAN compilers were individually priced at $275. Additionally, Locus provided a DOS Merge virtual machine that enabled MS DOS 3.3 applications to run within AIX, sold separately for $250. IBM also marketed an AIX PS/2 DOS Server Program at $150, offering file and print server capabilities for PC DOS clients.

The last iteration of PS/2 AIX was version 1.3, released in 1992, which extended support to non-IBM (non-microchannel) hardware. Official support for PS/2 AIX concluded in March 1995.

IBM mainframes

In 1988, IBM launched AIX/370, developed by Locus Computing Corporation, representing its fourth attempt to deliver Unix-like capabilities on the System/370 mainframe platform. Earlier initiatives included a TSS/370-based Unix system developed with AT&T around 1980, VM/IX created with ISC circa 1984, and IX/370—a VM/370-based TSS/370 variant enhanced for compatibility with UNIX System V. Released in 1990, AIX/370 provided functional parity with System V Release 2 and incorporated features from 4.3BSD alongside IBM-specific enhancements.

Following the introduction of the ESA/390 architecture, AIX/ESA succeeded AIX/370 in 1991. This version was built upon OSF/1 and operated on the System/390 platform. Unlike its predecessor, AIX/ESA could function both as a native host operating system and as a guest running under VM. Despite its technical sophistication, AIX/ESA experienced limited commercial adoption partly because Unix functionality became available as an optional component within IBM’s existing mainframe OS, MVS, through MVS/ESA SP Version 4 Release 3 OpenEdition released in 1994. This Unix capability continued in subsequent releases such as MVS/ESA SP Version 5, OS/390, and z/OS under the designation Unix System Services. IBM also provided OpenEdition support within VM/ESA Version 2 through to z/VM.

IA-64 Platforms

Within the scope of Project Monterey, IBM introduced a beta test release of AIX 5L tailored for the IA-64 (Itanium) architecture in 2001. However, this version never transitioned into an official product due to insufficient market demand.

Apple Network Servers

The Apple Network Server (ANS) lineup consists of PowerPC-based server machines engineered by Apple, featuring advanced capabilities such as hot-swappable hard drives, redundant power supplies, and external system monitoring. These servers were derived from contemporary Power Macintosh hardware and operated a customized AIX variant (versions 4.1.4 or 4.1.5) known as AIX for Apple Network Servers. This specific AIX edition was exclusive to ANS hardware and was not adapted for standard Power Macintosh systems. It is distinct from Apple's earlier Unix system, A/UX, which targeted 68k Mac architectures.

POWER ISA/PowerPC/Power ISA-based Platforms

The debut of AIX version 3 (AIX/6000) coincided with the launch of the initial POWER1-based IBM RS/6000 models in 1990. This release introduced several significant advancements, including the journaling file system (JFS) that accelerated boot processes by eliminating full disk checks during reboot, and shared libraries that minimized binary sizes and memory consumption by removing static linking requirements.

Version 3 also discontinued the microkernel design present in version 2, resulting in a streamlined architecture that no longer included PL.8 components.

Key subsystems featured:

IRIS GL, a 3D graphics library licensed from SGI, which served as a forerunner to OpenGL. SGI provided the entry-level graphics card for RS/6000 capable of rendering 20,000 gouraud-shaded triangles per second; IBM developed the high-performance graphics card modeled after the mainframe-attached IBM 5080, delivering up to 990,000 vectors per second.
PHIGS, a widely utilized 3D graphics API in automotive CAD/CAM applications and integral to CATIA.
Comprehensive support for X Window System version 11 with Motif as the default widget toolkit.
Compatibility with network file systems such as Sun Microsystems' NFS, Andrew File System (AFS), and Distributed File System (DFS).
Network Computing System (NCS) licensed from Apollo Computer (later acquired by HP).
Display PostScript (DPS) offered as an alternative graphical interface; however, its proprietary license and lack of 3D support limited its adoption compared to the X11 plus Motif combination.

Moreover, applications designed for AIX can execute within the PASE environment under IBM i.

Source Code

IBM made the AIX source code for RS/6000 accessible to customers at a cost; for instance, in 1991, obtaining AIX 3.0 source code required a one-time payment of US$60,000. Subsequent versions included AIX 3.1 released in 1992 and AIX 3.2 in 1993. These distributions omitted certain third-party components and layered software such as the MS-DOS emulator and C compiler. Licensing also mandated customers to secure agreements with AT&T and the University of California, Berkeley.

POWER/PowerPC/Power ISA Releases

Version	Release date	End of support date
5L 5.1	2001-05-04	2006-04-01
5L 5.2	2002-10-18	2009-04-30
5L 5.3	2004-08-13	2012-04-30
6.1	2007-11-09	2017-04-30
7.1	2010-09-10	2023-04-30
7.2	2015-12-04	TBA
7.3	2021-12-10	TBA

Released in December 2021, AIX V7.3 requires POWER8 or later CPUs and introduces enhanced features tailored for enterprise-grade environments.
The October 2015 release of AIX V7.2 brought capabilities such as live patching for fixes and service packs, flash-based filesystem caching, cluster-aware automation tools, SRIOV-enabled virtual network adapters, Oracle RDSv3 support over RoCE, and secure boot functionality on POWER9 processors; it demands POWER7 or newer CPUs.
AIX V7.1, launched in September 2010, supports up to 256 cores or 1024 threads per logical partition (LPAR), workload partitioning, XML-driven system configuration management, Fibre Channel adapter exportation to WPARs, cluster awareness features, event infrastructure enhancements, and role-based access control; it requires POWER4 or later CPUs.
Introduced in November 2007, AIX V6.1 added Workload Partitions (WPARs), Live Application and Partition Mobility capabilities, strengthened security measures including RBAC and Trusted Execution environments, encrypting JFS2 filesystems, integrated error reporting systems, concurrent kernel maintenance support, ProbeVue dynamic tracing tools, and filesystem snapshot functionality; this version supports POWER4 or newer CPUs but was withdrawn from marketing in April 2016 with support concluding in April 2017.
The AIX 5L series (versions 5.1 through 5.3) incorporated features such as NFSv4 support, advanced accounting mechanisms, virtualized SCSI/Ethernet interfaces, simultaneous multithreading (SMT), micro-partitioning on POWER5 hardware platforms, JFS2 quotas with filesystem shrinking capabilities, and dynamic kernel scheduler improvements.
Earlier iterations from AIX version 4.x introduced online backup utilities, workload management solutions, compliance with trusted computing base standards, IPv6 network protocol support, web-based system administration tools, multimedia service integration, and compatibility with RS/6000 systems utilizing PowerPC processors.
The initial releases (AIX versions 3.x) featured foundational technologies like the Journaled File System (JFS), Logical Volume Manager (LVM), and graphical desktop environments based on X.desktop.

This chronological overview underscores IBM's commitment to virtualization technology advancement, enhanced security frameworks, scalable solutions suited for enterprise workloads, and seamless integration with evolving Power architecture processors to address critical business computing needs effectively.

IBM System/370 Versions

AIX/ESA Version 2 Release 2
- Publicly revealed on December 15, 1992
- Released on February 26, 1993
- Discontinued as of June 19, 1993
- Operates exclusively in S/370-ESA mode

AIX/ESA Version 2 Release 1
- Announced on March 31, 1992
- Made available from June 26, 1992
- Support ended June 19, 1993
- Functions only in S/370-ESA mode

AIX/370 Version 1 Release 2.1
- Announcement date: February 5, 1991
- Available starting February 22, 1991
- Support withdrawn December 31, 1992
- Incompatible with XA, ESA, or z modes

AIX/370 Version 1 Release 1
- Announced March 15, 1988
- Released February 16, 1989
- Does not support XA, ESA, or z modes

IBM PS/2 Versions

AIX PS/2 v1.3, October 1992
- Removed from US market sales in March 1995
- Provided compatibility with IBM ThinkPad 750C laptops (1994)
- Introduced support for non-PS/2 hardware (1993)

AIX PS/2 v1.2.1, May 1991
AIX PS/2 v1.2, March 1990
AIX PS/2 v1.1, March 1989

IBM RT Versions

AIX RT v2.2.1, March 1991
AIX RT v2.2, March 1990
AIX RT v2.1, March 1989
- Included X Window System on installation media

AIX RT v1.1, released in 1986
AIX RT v1.0, released in 1985

User Interfaces

Until version 3, the default command shell was the Bourne shell, after which version 4 adopted the KornShell (ksh88) to comply with XPG4 and POSIX standards.

Graphical Interface

The standard graphical interface for AIX is the Common Desktop Environment (CDE). Additionally, through Linux Affinity and the complimentary AIX Toolbox for Linux Applications (ATLA), users have access to open-source desktop environments such as KDE and GNOME.

System Management Interface Tool

SMIT serves as the graphical system management utility for AIX, allowing administrators to navigate through a menu-driven command hierarchy instead of directly typing commands. It is commonly launched using the smit command. Advanced users often press F6 to display the exact command line that SMIT will execute.

Commands executed via SMIT are recorded in a smit.script file that logs all flags and parameters; this script can be reused for automating system configuration tasks. Additionally, SMIT generates a smit.log file containing detailed information beneficial for developers enhancing the tool.

The terms smit and smitty refer to the same utility; however, smitty opens the text-based interface exclusively, while smit tries to launch an X Window System interface if a graphical environment is detected via the DISPLAY environment variable; otherwise it defaults to text mode.

Database

Object Data Manager (ODM) is the native database within AIX that holds system configuration information and resembles the Windows registry in purpose. It organizes system data as objects with associated attributes critical for managing various aspects of the operating system.

Access to ODM data is provided through application programming interfaces and command-line tools such as odmshow, odmget, odmadd, odmchange, and odmdelete, enabling both scripting and interactive management. SMIT and other standard AIX commands also read from and write to ODM data. The ODM database is stored on disk utilizing Berkeley DB file structures.

ODM maintains key system details including:

Network setup configurations
Logical volume manager settings
Information about installed software packages
Definitions of logical devices and device drivers
Lists of supported hardware devices
Physical hardware inventory data
Menu layouts, screen definitions, and commands used by SMIT

References