Installing ReactOS

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Icon speedy deletion.png Warning: Please bear in mind that ReactOS is still in alpha stage, meaning it is not stable or feature-complete and is not recommended for everyday use. Operating system bugs can and do result in corrupted file systems, overwritten partitions, and more. Do not install ReactOS on any computer containing important data without using a virtual machine or making full backups first.

Before installing

There are several things to be made aware of before installing ReactOS, or even obtaining the installation media. These include how ReactOS will be installed, limitations of the installation, and backing up existing data.


ReactOS is alpha level (or alpha phase) software. It is not yet feature complete.
Some major bugs remain to be corrected. For the details see Known Issues. Bear in mind that this is not a complete list of known issues. See also Missing ReactOS Functionality.

The ReactOS itself, setup utility and boot loader have a number of limitations. The most prominent are:

  • ReactOS is not able to boot from USB devices yet. Except RAM Boot method.
  • the setup utility does not prevent users from performing dangerous and potentially destructive operations.
  • some SATA controllers may not work with ReactOS.
  • the boot partition is highly recommended be the first FAT16 or FAT32 partition on the first (or even better - single) disk in the system.
  • the setup utility can check the integrity of ONLY FAT16 and FAT32 file systems.
  • HD Audio or use of multiple audio cards at the same time are not yet supported. ReactOS versions and builds prior 0.4.12 will not boot after setup.

System requirements

Hardware support

ReactOS has limited hardware support. Lists of particular hardware that have been tested can be found on the page Supported Hardware.

Minimum hardware requirements

The minimum requirements to install ReactOS are:

  • RAM: at least 64 MB, recommended 256 MB, and even 2048 MB if you want to test large software suites or bundles.
  • Processor: x86 or x64 architecture, Pentium or later and compatibles; for more information see ReactOS ports.
  • HDD: IDE/SATA with minimum 450 MB of free space on the primary partition (please note that some SATA controllers may not work with ReactOS):
    • FAT16/FAT32 primary boot partition.
  • Video: VGA compatible video card (VESA BIOS version 2.0 or later).

Getting ReactOS

Due to the current state of the project, the ReactOS Foundation does not offer official installation media for distribution. Installation CD-ROMs must be created by the user by writing an available image file to a CD-ROM.

Downloading the image file

Official ISO image files can be downloaded at one of the following locations:

WARNING: Some anti-malware programs will detect false positives in ReactOS files.

Creating the Installation CD

The downloaded file is a compressed archive in ZIP format, containing a single file named "ReactOS.iso". The ISO image contains everything needed to create the CD.

  • Extract the image file from the archive into a temporary directory.
  • Burn the ISO image to a CD-R or CD-RW using any software of your choice.

When burning the ISO to disc, be sure it is written as an image file. Writing to the disc as another type of data will not work and render the Installation CD unbootable. Look for an option similar to "Burn from ISO" or "Write disk image".

Installing ReactOS

Please consider making full backups of any sensitive data before you start any experiments with ReactOS in the production environment!

Installation strategy

The first consideration to make is whether to install ReactOS on a dedicated testing machine or in a contained environment, such as running on an emulator without direct disk access. The use of an emulator is preferable if the machine on which you will run ReactOS is your primary computer or if you have important data on the computer which you cannot afford to lose.

If you decide to install ReactOS on a disk drive that contains an existing operating system (such as Microsoft Windows XP), you should ensure that the drive is formatted with a file system ReactOS can access and write to (now, primary FAT32/FAT16 partition) and that there is sufficient free space on the drive such that ReactOS can be installed (now, >=450 MB). Furthermore, the current hardware limitations to which ReactOS is constrained must be identified and compared to the target computer system (e.g. that ReactOS has only basic audio support as of 0.4.12 release).

Once the available hardware and software situation is determined the installation media can be selected. For most cases, USB-RAM boot should be enough (or CD-ROM boot for virtual machines). But sometimes it may either not work or be not available for the particular system. Then you can use other available options as well.

ReactOS goes through three stages during setup. The first two stages deal with the installation of the system, while the third stage is the first usable boot by the user.

  • First stage – Text mode setup, started when booting from a ReactOS CD-ROM.
  • Second stage – Booting to GUI installer. Input of user information and registering of files.
  • Third stage – Booting to desktop, user configurations.

If you encounter problems, disable all secondary or unnecessary devices, especially USB-cameras and sound cards of any type.

Virtual Machines

A Virtual Machine is a software program that provides a virtual hardware platform. Software instructions that would be run on hardware are now interpreted by the emulator software. This allows you to "run" a different kind of computer hardware and its software in a window on your computer.

See article Virtualization software for the details.

Real hardware

Note For the real hardware experiments, we recommend you to use our "official" Dell Latitude D531 laptop or similar notebook models in order to achieve the best possible experience.

USB-RAM boot

For this method, you should prepare a flash drive first. It should have a FAT32 filesystem and the Multiboot specification-capable bootloader should be installed on it. For example, you can use syslinux. Here is how to install it (for syslinux version 6.x):

On Linux

Plug in the flash drive and leave it unmounted. Then run these commands:

sudo mkfs.vfat /dev/sdb1
sudo syslinux --install /dev/sdb1

Note: here, /dev/sdb1 is a partition on a flash drive

On Windows

Use Rufus tool

  • Select your flash drive
  • Format it using the options (Partition scheme: MBR, Boot selection: Syslinux 6.x, File system: FAT32)

At this point, you should have a bootloader installed onto the drive. Now it's time to copy some files onto it.

(Download all the required files, except iso images in a zip-archive. It uses freeldr.sys from the fb4591c48c568d138d9d7aeaa90db4bd5885c6aa commit)

  • Now you need to copy mboot.c32 and libcom32.c32 syslinux libraries to the root
  • Then copy a freeldr.sys bootloader from ReactOS 0.4.13 or higher
  • Now you need to write some configuration files. First, syslinux.cfg:
  KERNEL mboot.c32
  APPEND /freeldr.sys
  • Then freeldr.ini:

TitleText=ReactOS LiveUSB
TimeText=Seconds until highlighted choice will be started automatically:

[Operating Systems]
LiveCD_Debug="LiveCD (Debug)"
LiveCD_Screen="LiveCD (Screen)"
BootCD_Debug="BootCD (Debug)"
BootCD_Screen="BootCD (Screen)"







Note: for detailed explanation, see Boot options

  • Now place bootcd.iso and/or livecd.iso in the root of the disk (or whatever path configured in freeldr.ini)
  • Ready to boot

Ordinary CD-ROM method

  • Make sure your BIOS is configured to boot from the CD-ROM first.
  • Insert the ReactOS setup CD-ROM into a CD-ROM drive and reboot your computer. On the next boot, the ReactOS setup utility will start.
  • Follow the instructions on the screen to install ReactOS on your computer.
  • After the installation has finished, remove the setup CD-ROM from the CD-ROM drive and press Enter to reboot your computer. You can now start ReactOS by selecting it from the boot menu.

Using another computer

  • create a virtual Machine but without the Harddisk
  • create a virtual Harddisk for Virtualbox which points to the real one.
    • on Linux: VBoxManage internalcommands createrawvmdk -filename "~/VirtualBox VMs/reactos/disk.vmdk" -rawdisk PathToHarddisk
    • important: PathToHarddisk must be the whole disk, not a partition: /dev/sdb
  • add disk.vmdk to virtual Machine via Storage->add Harddisk
  • install reactos as usual

Network boot or network installation via PXE

See article Building PXE-ready ReactOS

USB Installation

Due to problems with the USB stack it is NOT currently possible to install ReactOS from a USB stick made directly from iso file. This worked previously but was broken several years ago by a rewrite of the USB code. Use USB-RAM method instead

Or try these unofficial experimental builds

Installing drivers

You may also be interested in how to install a driver for a device in ReactOS. If so, see Install a driver article.

Unattended Installation

You may also be interested in how to install ReactOS in the automatic (non-interactive) mode. If so, see Create an unattended Installation CD article.

See also

  • VirtualBox – a free virtualization software for Windows, Linux and Mac (HOWTO)
  • QEMU – an open source machine emulator