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ArcaOS Logo
ArcaOS 5.0.5 desktop
DeveloperArca Noae, LLC (based on code from IBM, Microsoft, and other developers)
Written inC, C++, REXX, Java, assembly language
OS familyOS/2
Working stateCurrent
Source modelClosed source with open-source components
Initial releaseMay 15, 2017; 7 years ago (2017-05-15)[1]
Latest release5.1.0 / August 27, 2023; 10 months ago (2023-08-27)[2]
Package managerANPM (based on RPM and YUM)
Platforms32-bit x86
Kernel typeHybrid kernel
user interface
Workplace Shell, cmd
LicenseProprietary software

ArcaOS is an operating system based on OS/2, developed and marketed by Arca Noae, LLC under license from IBM.[3][4] It was codenamed Blue Lion during its development.[5] It builds on OS/2 Warp 4.52 by adding support for new hardware, fixing defects and limitations in the operating system, and by including new applications and tools,[6] and includes some Linux/Unix tool compatibility. It is targeted at professional users who need to run their OS/2 applications on new hardware, as well as personal users of OS/2.[7]

Like OS/2 Warp, ArcaOS is a 32-bit[8] single user, multiprocessing,[9] preemptive multitasking[10] operating system for the x86 architecture.[11] It is supported on both physical hardware[12] and virtual machine hypervisors.[13]


Hardware compatibility

ArcaOS supports symmetric multiprocessing systems with up to 64 processor cores, although it is recommended to disable hyperthreading.[9] As of version 5.0.8, ArcaOS is ACPI 6.1-compliant and includes the 20220331 release of ACPICA.[14]

While ArcaOS is a 32-bit operating system, it has limited PAE support which allows it to use RAM in excess of 4GB as a RAM disk.[7]

ArcaOS supports being run as a virtual machine guest inside VirtualBox, VMware ESXi, VMWare Workstation and Microsoft Virtual PC.[13]

In addition to the device drivers included with OS/2 Warp 4, ArcaOS includes a variety of drivers developed by Arca Noae, and various third parties:


Some of the open source software included with ArcaOS - Firefox, Lucide, 4OS2, PMDCalc Plus

In addition to the software bundled with OS/2 Warp 4, ArcaOS includes some additional software, such as:[26][27][28]

Cross-platform compatibility

Some of the compatibility subsystems in ArcaOS - a Bash shell (bottom left), QBASIC in a DOS window (middle), and the Windows 3.1 Program Manager (top right)

ArcaOS includes a number of software components which allow it to directly run software developed for other operating systems, and to simplify the process of porting software to ArcaOS:


ArcaOS's default filesystem is JFS, although HPFS is also supported for backwards compatibility.[36] ArcaOS may be installed to and booted from either filesystem.[37]

FAT12, FAT16, and FAT32 are also supported using either the OS/2 kernel's own FAT driver, or a new Arca Noae-developed FAT32 IFS driver, included in ArcaOS since version 5.0.3.[38] ArcaOS includes support for optical disc filesystems such as ISO 9660 and UDF.[39]

ArcaOS supports serving and accessing CIFS/SMB shares using the open source Samba project, and provides a graphical utility named ArcaMapper to manage configuration.[40]

NetDrive for OS/2 provides access to a variety of additional filesystems such as NTFS and NFS via its own IFS driver.[41][42] The ArcaOS distribution includes a limited license version of NetDrive but the fully licensed version is capable of mounting a number of other local, native, and foreign file systems.[43]

Installation and updates

The hardware configuration screen from the ArcaOS installer

ArcaOS features a new graphical installer which replaces the IBM installer used in OS/2 Warp.[44] Unlike OS/2, the ArcaOS installation process does not require a boot floppy, and instead the installer can be booted directly from optical media, or from a USB flash drive.[45] The installer also provides an update facility, which allows ArcaOS to be updated to the latest release without reinstalling the entire operating system.[46]

Installation and updates of individual software packages is provided through the Arca Noae Package Manager (ANPM), which consists of a native OS/2 graphical frontend on top of RPM and YUM.[47] Software is provided through a mixture of freely available, and subscription only RPM repositories.[48]

Hardware requirements

The minimum hardware requirements for ArcaOS 5.1 are as follows:[11]

Processor Intel Pentium Pro or AMD K6
Memory (RAM) 256MB minimum

2GB recommended

Graphics card VGA video card with VBE 2.0 support[49]
Storage space 2GB of available disk space
Removable media Installation requires DVD-ROM drive or USB flash drive
Firmware Traditional BIOS, UEFI, or UEFI with CSM.
Input devices PS/2 or USB keyboard and mouse


Blue Lion

ArcaOS was formally announced on October 23, 2015, at the Warpstock 2015 event (an OS/2 user group event) under the code name "Blue Lion" by Arca Noae's Managing Member, Lewis Rosenthal.[4][5]

Some of the planned features for Blue Lion announced at the time were:[4]

ArcaOS 5.0

The name "ArcaOS" was first published in a TechRepublic article[52] on May 26, 2016, while the domain was registered December 20, 2015. In the same TechRepublic article, Lewis Rosenthal was quoted as saying that the first release of ArcaOS would be version 5.0, as it follows onto the last release of OS/2 Warp from IBM, which was 4.52 (also known as Merlin Convenience Pack 2, or MCP2).[53]

ArcaOS 5.0 was released May 15, 2017.[1] There were two editions released: a commercial edition, intended for enterprise use (including 12 months of upgraded/prioritized technical support), and a personal edition, targeted at non-business users (including six months of standard technical support) at a reduced price.[54] Pricing was listed as $229 per license for the commercial edition, and $129 per license for the personal edition, with $99 promotional price in effect for the first 90 days following release.

ArcaOS 5.0 was followed by a number of maintenance releases between 2017 and 2023. In addition to bug fixes and driver updates, the maintenance releases added some significant features such as USB 3.0 support, support for NVMe drives, the ability to install from a USB drive, and the update facility.[28]

ArcaOS 5.1

Prior to the release of ArcaOS 5.0, ArcaOS 5.1 was originally planned for release in 2017 with a focus on supporting other languages including French, Spanish, Italian, German, and Dutch.[52] Following the release of ArcaOS 5.0, Arca Noae began discussing a 5.1 release in their roadmaps, along with proposed new features.[55] ArcaOS 5.1.0 was released on August 27, 2023, adding support for booting on UEFI Class 3 systems, and support for GUID partition tables — allowing for disks larger than OS/2's previous 2TB size limit.[56]

Other features which have been proposed for the 5.1.x releases include:

Release history

ArcaOS releases
Release Date Major changes[28][61]
5.0 2017-05-15[1] First public release of ArcaOS
5.0.1 2017-07-09[62] Installer fixes and driver updates
5.0.2 2018-02-10[63] Added ability to boot from USB media
5.0.3 2018-08-19[64] Updates to software and drivers
5.0.4 2019-07-21[65] Update facility which allows ArcaOS to updated without reinstalling
5.0.5 2020-06-06[19] USB 3.0/xHCI support
5.0.6 2020-08-31[66] Installer fixes and updates
5.0.7 2021-12-07[67] NVMe driver
5.0.8 2023-06-01[68] Support for NVMe drives in installer and preboot environment
5.1.0 2023-08-27[2] Support for UEFI Class 3 hardware, and GPT partitions


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  2. ^ a b "ArcaOS 5.1.0 now available". 2023-08-27. Retrieved 2023-08-27.
  3. ^ "ArcaOS 5.0 from Arca Noae is the new release of OS/2 for the 21st century".
  4. ^ a b c Blue Lion Announcement at Warpstock 2015
  5. ^ a b James Sanders (2015-11-02). "OS/2: Blue Lion to be the next distro of the 28-year-old OS". Archived from the original on 2015-11-06. Retrieved 2023-09-04.
  6. ^ "About ArcaOS". Retrieved 2020-08-31.
  7. ^ a b c Lunduke, Bryan (23 May 2017). ""OS/2 Based ArcaOS" - Lunduke Hour - May 23, 2017" – via YouTube.
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  13. ^ a b "Virtual Machine Configuration". Retrieved 2020-09-05.
  14. ^ "Readme for the ACPI Driver Package". Retrieved 2023-09-04.
  15. ^ Arca Noae wiki: MultiMac NIC Drivers
  16. ^ Project: Generic MAC Wrapper Driver (GenMac)
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  21. ^ Arca Noae wiki: Panorama Video Driver
  22. ^ Arca Noae wiki: Arca Noae SNAP Graphics for OS/2
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  33. ^ "Getting to know the Unix Compatibility Subsystem (kLIBC)". Retrieved 2020-09-08.
  34. ^ a b "Compatibility Subsystems". Retrieved 2020-09-08.
  35. ^ "Lucide Building Instructions". Retrieved 2020-09-22.
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  37. ^ "Installation Planning". 2020-06-06. Retrieved 2020-09-22.
  38. ^ "FAT32 Installable File System Driver". Retrieved 2020-09-04.
  39. ^ "DVD/UDF". Retrieved 2020-09-22.
  40. ^ "ArcaMapper". Retrieved 2020-09-22.
  41. ^ "Network File System (NFS) plugin for NetDrive". Retrieved 2020-09-22.
  42. ^ "NTFS plugin for NetDrive". Retrieved 2020-09-22.
  43. ^ "NetDrive for OS/2". Retrieved 2020-09-22.
  44. ^ "Writing the ArcaOS installer". 2017-10-06. Retrieved 2020-09-22.
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