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Subject: Boot flag, Boot loaders, Multi-booting, Comparison of boot loaders, Partition type
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xOSL (meaning Extended Operating System Loader) is the name of a bootloader, which is a program product class that launches operating systems from a bootable device such as a hard disk or floppy drive. xOSL was originally developed by Geurt Vos.


  • Basic appeal 1
  • History 2
  • Survivability 3
  • Notes on using XOSL with Windows 7, Windows 8, Windows 8.1 and U/EFI BIOS 4
    • 0) Create OS images without knowledge of other OS's. 4.1
    • 1) Make sure you have bootmgr.exe and BCD on same partition as Windows. 4.2
    • 2) Make sure that the BCD is "generalized" before imaging. 4.3
  • XOSL-OW 5
  • Compatible file-systems 6
  • Conclusions 7
  • External links 8

Basic appeal

xOSL provides a graphical user interface which allows the user to set up and boot a computer into any of 24 different operating systems. xOSL is nondenominational bootloader, owing allegiance to no system in particular, and booting them all equally well.

The xOSL interface installs and uninstalls easily. The xOSL program poses very little risk of permanent damage to existing data. Removing the program can be accomplished with the DOS command fdisk /MBR, which returns the disk to its original boot configuration. Generally Xosl resides on its own fat32 partition requiring less than 2mb, and it does not intermingle with other data.

If xOSL is installed on a DOS partition the configuration files are marked as hidden. They all have a filetype beginning with 'X' (.XCF, .XXF, .XDF) You can see the xOSL files with the command "dir /a /w *.x*".

The xOSL solution is highly portable (less than 1 MB) and incorporates easily navigable menu boxes and interfaces. The program requires very little time to configure.

Note: The 24 system limitation is imposed by the physical space available on the operating system menu. Theoretically, the program could support an infinite number of operating systems. By 'chainloading' the bootloader, users have reported booting vastly more operating systems than the program is claimed to support.[1]


xOSL is free software released under the GPL license. The project was actively developed by Geurt Vos between 1999 and 2001 and spanned four major revisions and two minor revisions after its initial creation.

From its origin in xOSL version 1.0.0, xOSL underwent major changes in ver. 1.1.0, 1.1.1, 1.1.2 and 1.1.3. These revisions were significant departures from one another, and introduced new features to the program. These features ranged from drastic user interface improvements to improved compatibility on diverse hardware platforms.

xOSL ver. 1.1.4 and 1.1.5 only introduced improvements to existing functionality and repaired features that should have been functional in their predecessors. Although their improvements were subtle, they did serve to stabilize a developing protocol, and are the most polished revisions of the original to date.

The project lapsed into a dormant state and was abandoned by its original developer from 2001-2007. xOSL remained available for download and use throughout this period.


Despite the lack of active product development, an enthusiastic community of xOSL users began exchanging ideas and product results through the use of Yahoo! Groups and other support sites on the internet. These groups became the foundation of the 'xOSL Culture'. The xOSL groups assisted fellow members with advice and accomplishments through the use of xOSL. After the original xOSL web site expired it was mirrored in multiple locations by Filip Komar and Mikhail Ranish.

The cult-like devotion to xOSL gave credibility to the idea that the future development of xOSL was an inevitability. Other bootloaders such as Lilo and GRUB performed effectively, but xOSL survived as time passed without development support or a marketing platform of any kind.

Very few enhancements to the original product occurred during this time, most of them being fairly inconsequential. One such enhancement gave the user the ability to change wallpapers and the image displayed at startup, and like most other revisions, it did not add a great deal to the program in terms of core functionality.

Other revisions included the translation of xOSL into several different languages, including German, Czech and French, among others.

Notes on using XOSL with Windows 7, Windows 8, Windows 8.1 and U/EFI BIOS

Despite its advanced age the original XOSL Ver 1.5.1 can be used very successfully with the latest releases of Windows and with the UEFI or EFI BIOS that have been shipped on motherboards since 2012. Knowledge of the points listed below will get you on your way multi-booting these modern OS's.

Since Vista, the way the boot sequence works has changed to use bootmgr.exe instead of ntloader.exe and is configured using BCD instead of boot.ini. See: Boot Methods for Old Windows and New Windows

0) Create OS images without knowledge of other OS's.

This suggestion applies to all OS's (Linux, Windows 98 to Windows 8). If a newly installed os sees other os's on different partitions, the new OS will become the boot manager for the old OS's and the new install will be a mess if you wish to clone it and use it as one of your multiboot OS's.

A common use case for multiboot of Windows is to have a partition that you use to testing such things as installs of downloaded software before installing them in your daily use working partition. So you will want to make an image of your freshly installed Windows and be able to repeatedly overwrite your testing partition with it as necessary. So having a clean install of Windows without it knowing of any other OS's will make it independent.

So first format your hard drive with a single NTFS partition and a MSDOS partition table in the Master Boot Record using a tool such as the open source gparted. Then install Windows onto that partition and make an image of it.

Note that Win7+ can be imaged with older imaging tools when booting the imaging tool from the image tool CD (versus installing it on your OS). For example Acronis TI Home 2011 can image Windows 8.1 when you boot from the CD assuming that the following steps are taken.

1) Make sure you have bootmgr.exe and BCD on same partition as Windows.

If a Windows 7+ installer is booted in U/EFI mode, then Windows will want to install to the ESP (EFI System Partition), a hidden FAT32 formatted boot partition. On most motherboard lacking proper NTFS drivers, this makes it impossible to have a single partition image that contains everything needed to run. ASUS UEFI motherboards ship with a working NTFS driver, and are able to call bootmgfw.efi directly.

If you cannot locate an NTFS driver, you can disable UEFI boot, or use the CSM to choose between UEFI and BIOS. To do this, follow the steps in your motherboard's user manual. After doing this, when win7+ is installed it will place the bootmgr and BCD onto the same partition, if you formatted and made active install partition prior to installing. After install, verify that the boot folder and bootmgr.exe are on the root of C:.

Another more painful option is to copy the bootmgr and boot folder from the hidden partition to the root of your install partition and mucking with a few other things see: Removing the Hidden Partition for more details.

2) Make sure that the BCD is "generalized" before imaging.

Make sure that the BCD is "generalized" and not locked to a specific hard drive or partition before you make an image of that partition. This will allow that image to be located on any partition and will prevent it from using the MBR signature.

The bootmgr.exe will fail once XOSL is installed since bootmgr uses the MBR signature to determine which hard drive to boot from and XOSL overwrites the MBR changing its signature. This can be fixed by using Microsoft's bcdedit tool to make the BCD "generalized" with the following commands:

bcdedit /set {current} osdevice boot
bcdedit /set {current} device boot
bcdedit /set {bootmgr} device boot
bcdedit /set {memdiag} device boot

It is easiest to do this after installing Windows and booting into Windows (and do it BEFORE installing XOSL) since you can then do it from an administrator command prompt without jumping through many hoops.

For complete instructions on how to do this including doing it from the Win install CD see: Details on preparing a partition for imaging.


XOSL-OW is an Open Watcom Port of XOSL. XOSL is developed by Geurt Vos using the Borland C++ 3.1 tool set while XOSL-OW is based on the Open Watcom version 1.8 tool set. The XOSL-OW Open Watcom Port allows for future development of XOSL using an Open Source development tool set.

XOSL-OW has no new functionality compared to XOSL but it does give improved behavior on specific PC hardware. In fact stability issues with XOSL on some PC platforms have been the reason for porting XOSL to the Open Watcom tool set.

Examples of stability issues on specific PC hardware are:

  • Launching the Ranish Partition Manager from within the XOSL boot manager (Ctrl-P) results in a non-responsive keyboard.
  • Booting into the Smart Boot Manager (used to support booting from CD/DVD) results in a non-responsive keyboard.
  • Booting into Linux using the XOSL boot manager is not successful because of a non-responsive keyboard after the XOSL boot manager hands over control to the Linux boot process.

In XOSL-OW these stability issues have been solved by an improved A20 Line Switching algorithm and flushing the keyboard buffer before the XOSL boot manager hands over control to either the Ranish Partition manager, the Smart Boot Manager or the Operating System Bootloader.

Compatible file-systems

Currently xOSL is capable of booting operating systems from a variety of format types. These include, and may not be limited to:


Other reasons for the success of xOSL include its compact size. Its primary location is in the MBR where it references items on the physical hard drive for its GUI and other features. As long as a drive is formatted in FAT32, xOSL does not require additional partitioning. The FAT32 drive on which xOSL resides does not need to be the first partition of the drive.

Other features include:

  • Graphical User Interface
  • Full windowing system with mouse and keyboard support
  • Resolutions up to 1600x1200
  • Configurable mouse speed
  • A set of color schemes
  • Several color adjustment options
  • Password protected boot configuration and settings
  • Restart/Reboot/Shutdown

Booting Features:

  • Up to 24 boot items
  • Microsoft file system partition hiding support
  • Storing additional keys before booting
  • Can automatically switch the boot flag to whichever partition is being booted. Although XOSL does not use the boot flag to decide which partition to boot, this helps to ensure that a Windows system being booted (for example Windows XP) will assign the letter "C:" to its partition.[2]
  • Automatic booting (with timeout)
  • Auto boot last operating system
  • Password protection per boot item
  • Boot master boot record on any drive
  • Boot DOS/Windows 9x on any drive
  • Hotkey per boot item
  • Support for hard disks larger than 8Gb
  • Coexists with virtually any other boot manager
  • Runs Ranish Partition Manager 2.38 beta 1.91 (ver 1.1.5 and above)
  • Master boot record virus protection

The continued development of xOSL is almost entirely dependent on individual user contributions and community participation.

External links

  • XOSL Hq(Official site)
  • XOSL Users Group at Yahoo
  • XOSL Historical Archive from 2000
  • xOSL and Windows Vista
  • XOSL Mirror at
  • xOSL2 Sourceforge Page
  • XOSL-OW Home page
  • Czech Translation
  • Understanding MultiBooting by Dan Goodell
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