# The dosemu HOWTO

Mike Deisher. Updated by Uwe Bonnes for dosemu-0.64.4, 15 March 1997. Updated by David Hodges, davidhodges@altavista.iname.com

For dosemu-1.2, 27 September 2003

This is the `Frequently Asked Questions' (FAQ) / HOWTO document for dosemu. The most up-to-date version of the dosemu-HOWTO may be found at http://www.dosemu.org.

## The preliminaries

### What is dosemu, anyway?

To quote the manual, "dosemu" is a user-level program which uses certain special features of the Linux kernel and the 80386 processor to run MS-DOS/FreeDOS/DR-DOS in what we in the biz call a `DOS box.' The DOS box, a combination of hardware and software trickery, has these capabilities:

- the ability to virtualize all input/output and processor control instructions

- the ability to support the word size and addressing modes of the iAPX86 processor family's "real mode," while still running within the full protected mode environment

- the ability to trap all DOS and BIOS system calls and emulate such calls as are necessary for proper operation and good performance

- the ability to simulate a hardware environment over which DOS programs are accustomed to having control.

- the ability to provide DOS services through native Linux services; for example, dosemu can provide a virtual hard disk drive which is actually a Linux directory hierarchy.

### What operating systems does dosemu work under?

Dosemu is primarily written for Linux. At one time it also worked on NetBSD and possibly FreeBSD, however the graphics emulation was unlikely to work on NetBSD, which means that all DOS programs that use graphics mode (most DOS programs) did not work under NetBSD.

### What processors does dosemu work on?

Dosemu only works on Intel 80x86 processors, e.g. 80386, 80486, Pentium etc.

### What if I have an Alpha/Sparc/Motorola/other non-Intel CPU?

Dosemu only works on Intel 80x86 processors but there are alternatives: Bochs (http://bochs.sourceforge.net) is an open source PC emulator that runs on most Unixes (as well as MS-Windows). DOSBox (http://dosbox.sourceforge.net) also emulates the CPU but specializes in DOS games. QEMU ( http://fabrice.bellard.free.fr/qemu/index.org.html) can launch Linux processes compiled for one CPU on another CPU. Wine and DOSEMU are the main targets for QEMU. There are other (non-free) alternatives - see the comp.emulators.misc FAQ, available via usenet or http://www.faqs.org/faqs/emulators-faq/

### Do I need MS-DOS to use dosemu?

No. You need some version of DOS but not necessarily MS-DOS. The supplied FreeDOS will do for almost all DOS programs. One notable exception is Windows 3.x. See also whatdosversion.

### Can I run Microsoft Windows programs under dosemu?

Yes, but it would be better to use the Windows emulator Wine (http://www.winehq.com). If you insist on running Windows under dosemu, see section 8 - dosemu and MS-Windows 3.1.

### I want to run something that won't run under DOSemu or Wine

See nonintel, or try VMWARE at http://www.vmware.com or Plex86 at http://www.plex86.org

### Names and numbers

(xx/yy/zz)

- means day zz in month yy in year xx.

winemu

- winemu mean WinOS/2 running in dosemu.

### What version of Dosemu should I use?

Dosemu uses the same numbering scheme as the kernel used. Uneven second numbers are for possible unstable developer releases, even second numbers are for releases considered stable. At the time of writing, `1.4.0` is the latest stable release, while `1.3.5` is the latest developer's release. So if you just want to use dosemu, get the latest stable release.

### What's the newest version of dosemu and where can I get it?

The newest stable version of dosemu as of 2007/05/05 is dosemu-1.4.0 and can be obtained at http://www.dosemu.org/.

We just decided to leave BETA stage, however: there may be serious bugs and very little documentation for new features. The development version is particularly likely to have bugs. Please use it only if you like to do active development. Preferably fix bugs in the development version instead of reporting them.

### Where can I ask questions?

If you have problems regarding installing and running dosemu after reading the documentation, first try to help yourself: Your question has probably been asked and perhaps answered before. Try some search engine on the internet to retrieve that information. E.g. you can ask http://groups.google.com to find all newsnet articles containing the keywords of your question. Helping yourself will probably be faster than asking a well known question. It also frees up the time of developers from answering trivial questions and so helps the further development of dosemu.

### Where can I report bugs and ask questions?

If you want to ask questions and report bugs regarding dosemu, you should consider subscribing to the linux-msdos mailing list. To subscribe, send mail to Majordomo@vger.kernel.org with the following command in the body of your email message:

    subscribe linux-msdos your_username@your.email.address

If you ever want to remove yourself from the mailing list, you can send mail to Majordomo@vger.kernel.org with the following command in the body of your email message:

    unsubscribe linux-msdos your_username@your.email.address

(95/8/11). When you are subscribed to linux-msdos, you can send your report as mail to linux-msdos@vger.kernel.org. There is a gate that send mails to linux-msdos@vger.kernel.org as postings to the newsgroup named linux.dev.msdos. If your News provider doesn't carry that group, ask her(him) to add that group. Before you ask a question, you should carefully read all of the documentation, including this HOWTO and check one of the mailing list archives listed at http://www.dosemu.org/mailinglist.html to see whether your question has already been asked and answered.

Alternatively, use the SourceForge Bug Tracking System for DOSEMU at http://sourceforge.net/tracker/?atid=457447&group_id=49784&func=browse . The advantage of this system is that your bug is less likely forgotten.

### What documentation is available for dosemu?

Dosemu comes with documentation. The main documentation files README.txt and README-tech.txt cover virtually all aspects of dosemu and may be more up-to-date than this HOWTO.

The "dosemu Novice's Altering Guide" or DANG is a road map to the inner workings of dosemu. It is designed for the adventurous, those who wish to modify the source code themselves. The DANG is maintained by Alistair MacDonald (alistair@slitesys.demon.co.uk) and is found in the doc directory of the dosemu source tree.

The EMU failure list (`EMUfailure.txt`) is a partial list of programs known not to work under dosemu.

And then, of course, there is the dosemu FAQ/HOWTO. But you already know about that, don't you. It is also posted once in a while to the mailing list and found in the doc-directory. The most recent version can be found at http://www.dosemu.org.

### I have a program that fails, not listed in EMUfailure.txt

First check, if the failure of your program is not caused by some of the fundamental incapabilities of dosemu, listed in `EMUfailure.txt`. If you think you have something new, please report to linux-msdos@vger.kernel.org. Perhaps it can be made going with the help others. Give detailed information about your setup, tell the version of kernel, dosemu etc and name the observed errors. You can use xdosemu to cut and paste the error message into your report. But keep your report in a readable form. We know the content of the commented out options. So only send the active lines from your `dosemu.conf` and `~/.dosemurc`. Try running dosemu with some or all debug output turned on and scan through your debug output and at first only send those parts you think are relevant. Few people are willing to decode some long attachment to a mail, to do debugging for others. But keep your logs at hand, in case others ask detailed questions.

### How do I submit changes or additions to the HOWTO?

The preferred method is to edit the file dosemu-HOWTO-xx.x.sgml to incorporate the changes, create a diff file by typing something like:

    diff -uw original-file new-file

and send it to linux-msdos@vger.kernel.org. If you do not know SGML, that's ok. Changes or new information in any form will be accepted. Creating the diff file just makes it easier on the HOWTO maintainer. :-)

### Message from Greg...

Unless otherwise stated, Linux HOWTO documents are copyrighted by their respective authors. Linux HOWTO documents may be reproduced and distributed in whole or in part, in any medium physical or electronic, as long as this copyright notice is retained on all copies. Commercial redistribution is allowed and encouraged; however, the author would like to be notified of any such distributions.

All translations, derivative works, or aggregate works incorporating any Linux HOWTO documents must be covered under this copyright notice. That is, you may not produce a derivative work from a HOWTO and impose additional restrictions on its distribution. Exceptions to these rules may be granted under certain conditions; please contact the Linux HOWTO coordinator at the address given below.

In short, we wish to promote dissemination of this information through as many channels as possible. However, we do wish to retain copyright on the HOWTO documents, and would like to be notified of any plans to redistribute the HOWTOs.

If you have questions, please contact Greg Hankins, the Linux HOWTO coordinator, at gregh@cc.gatech.edu(95/8/11).

## Compiling and installing dosemu

### Where are the installation instructions?

The installation instructions are in the file `INSTALL`, included in the distribution.

### Top problems while compiling and installing dosemu.

1. Forgetting to read the `README` and `INSTALL`.

2. Try to compile some old version of dosemu.

3. Use dosemu with a kernel that does not have `IPC` compiled in.

4. Compile with gcc older than 2.95.2, egcs older than 2.91.66 (1.1.2) or glibc older than 2.1.3.

5. Forgetting to use a dosemu-freedos-bin tarball when no other DOS is available on the system.

6. Run DOSEMU with partition access while they are already mounted.

### How do I make a.out binaries?

Starting with version `0.64.4` there is no a.out support any more. If you absolutely need it, you must use version `0.64.3.1`. The configure script then should take care for this, if your setup is a standard setup.

### How do I compile dosemu on a machine with low memory?

Marty Leisner leisner@sdsp.mc.xerox.com reported (95/4/8) that:

If you have problems with running out of swap space you may want to add `CFLAGS+=-fno-inline` after `CFLAGS` is defined in `src/dosext/dpmi/Makefile`. Be careful before you do this and check for the existence of swap space. I found Linux crashes at times when it has no swap space.

### Compilation fails with some strange error regarding "slang"

You probably have `plugin_slang off` in your compiletime-settings file. You need to change it to `plugin_slang on` and recompile.

### What configurable options are available?

The `compiletime-settings.help` file describes the options you can change at compile time. `README.txt` describes the options you can change at run time.

### Do I need to run dosemu as root?

No. Although most of dosemu drops root privilege after initialization, it is still safer to not run dosemu as root. Most normal DOS applications don't need dosemu to run as root, especially if you run dosemu under X. Thus you should not allow users to run a suid root copy of dosemu, wherever possible, but only a non-suid copy. You can configure this on a per-user basis using the `dosemu.users` file, or setup a configuration using sudo and use `dosemu -s` (see `INSTALL`).

Programs that require direct access to hardware ports (e.g. if the program needs to talk to some unusual hardware that is not supported by Linux and dosemu) require dosemu to run as root but printers, serial ports, mice, video cards and sound are emulated by dosemu so you won't usually need direct hardware access and won't need to run as root to use these. Some programs are just too sneaky for dosemu's hardware emulation to work properly though ...

You will need to edit `dosemu.users` (see `dosemu.users.example`) for any suid-root/sudo access beyond console graphics or run dosemu as root for hardware access.

### How do I patch dosemu?

If you do patch dosemu from one version to another, do "`make pristine;./configure; make`". If you don't make pristine, at least the version of the new executable will be wrong, if the whole thing compiles at all (97/2/9).

### What versions of DOS are known to run with dosemu?

All versions of DOS should work with dosemu, with the following caveats:

DOS 4.01 had problems by itself, so it won't work reliably with dosemu either.

With MsDos-7 aka Win95 you must not start the graphic shell at bootup. If you make the hdimage bootable with the so called "Rescue Disk" you are offered to make during the Windows installation, you get the right settings. If you use your normal Win95 installation to transfer the system files, have a look at the msdos.sys written on the hdimage and change the settings under the section [Options] to have entries like:

    [Options]
    Logo=0
    BootGUI=0

## Hard disk setup

### How do I use my hard disk with dosemu?

First, mount your dos hard disk partition as a Linux subdirectory. For example, you could create a directory in Linux such as `/dos` (mkdir -m 755 /dos) and add a line like:

    /dev/hda1       /dos     msdos   umask=022

to your `/etc/fstab`. (In this example, the partition is mounted read-only. You may want to mount it read/write by replacing "022" with "000" and using the -m 777 option with mkdir). Now `mount /dos`.

Now you can run (for instance) `lredir f: linux\fs/dos` at the DOS prompt to map drive F to /dos. Re-redirecting C using `lredir c: linux\fs/dos` works too but then you need to copy all your dosemu utilities (in `c:\dosemu`) to a place where they can still be found. If you want to boot via `/dos`, read on.

The `README.txt` says:

you just can have a Linux directory containing all what you want to have under your DOS C:. Copy your IO.SYS, MSDOS.SYS or what ever to that directory (e.g. `$HOME/.dosemu/bootdir`), put `$_hdimage = "bootdir"` into your `$HOME/.dosemurc`, and up it goes. Alternatively you can specify an absolute path such as "/dos" or "/home/username/dosemu/freedos". DOSEMU makes a lredir'ed drive out of it and can boot from it. You can edit `config.sys` and `autoexec.bat` within this directory before you start dosemu. Further more, you may have a more sohisticated setup. Given you want to run the same DOS drive as you normal have when booting into native DOS, then you just mount you DOS partition under Linux (say to `/dos`) and put links to its subdirectories into the boot dir. This way you can decide which files/directories have to be visible under DOSEMU and which have to be different. Here's a small and incomplete example bootdir setup:

    config.sys
    autoexec.bat
    command.com -> /dos/command.com
    io.sys -> /dos/io.sys
    msdos.sys -> /dos/msdos.sys
    dos -> /dos/dos
    bc -> /dos/bc
    windows -> /dos/windows

### How can I access the hdimage from Linux?

Use mtools. With a line in `/etc/mtools.conf` like:

    drive n:  file="/path/to/hdimage" MTOOLS_SKIP_CHECK=1 \
    MTOOLS_LOWER_CASE=1 MTOOLS_NO_VFAT=1 partition=1 offset=128

you can use the mtools on the hdimage, like "mdir n:". "mcopy n:/config.emu /tmp" copies the config.emu file from the hdimage to /tmp/config.emu. You can edit it there and copy it back. Use a drive letter you find sensible. "N:" is only an example.

### Can I use my stacked/double-spaced/super-stored disk?

At this time, compressed drives cannot be accessed via the redirector (lredir or emufs) on a standard kernel. There is a patch for the kernel to mount compressed files under the name "dmsdosfs". Find it on ibiblio.org and its mirrors http://ibiblio.org:/pub/Linux/system/filesystems/dosfs/. A good idea is also to look in http://ibiblio.org:/pub/Linux/Incoming for a newer version. The "wholedisk" option in older versions of dosemu is no longer allowed in recent versions, however, a line like

    $_hdimage = "/dev/hda1"

may work, if you have read and write access to this device and at the risk that you could lose all data in that partition on a dosemu crash. Also it is extremely dangerous to let two dosemu sessions access the partition at the same time.

If your dos partition is already mounted with write access and you try to run dosemu with partition access, dosemu will print a warning message and abort. This prevents DOS and Linux from making independent writes to your disk and trashing the data on your dos partition (95/8/11).

Holger Schemel q99492@pbhrzx.uni-paderborn.de reported (94/2/10) that:

Works even fine under dosemu with MS-DOS 6.0. If you have problems, then you have to edit the file `DBLSPACE.INI' manually and change the disk letter to the letter your drive gets under dosemu.

### Creating your own hdimage file.

There is an extra util program called mkfatimage16 which allows for creating a hdimage file headers. The full information is in the manpage (man/mkfatimage16.1) included in your distribution.

To create a hard disk image file with a geometry corresponding to that of a real hard disk of 32 megabytes run:

    mkfatimage16 -k 32768 > hdimage

This is probably too large for most needs; if you need this much space, consider using the disk redirector.

Usually it is a good idea to format the drive after it.

## Parallel ports, serial ports and mice

### Port access worked with older version, but doesn't work now!

Read `README.txt` and the port-section in `dosemu.conf`. Also, you must now you the -s dosemu command line switch.

### Port access was faster with older versions!

To have a chance to log port access, by default every port access produces an exception out of vm86-mode. This takes some time. If you don't want to log port access, use the keyword `fast` in the appropriate port statement.

### Where are the (microsoft compatible) mouse drivers?

Tom Kimball tk@pssparc2.oc.com reported (93/11/24) that:

Several people said to use a different mouse driver and suggested some. I found a couple that seem to work fine.

    oak.oakland.edu:/pub/msdos/mouse/mouse701.zip   (mscmouse)
    oak.oakland.edu:/pub/msdos/mouse/gmous102.zip   (gmouse)

Normally you can use dosemu's internaldriver, so you don't need any additional mousedriver in dosemu outside winemu (97/2/10).

### Why doesn't the mouse driver work?

Mark Rejhon mdrejhon@magi.com reported (95/4/7) that:

If you start the mouse driver and it just hangs (it might actually take 30-60s), but if you are waiting longer than a minute for the mouse driver to start, try specifying the COM port that the mouse is on, at the mouse driver command line.

### Why does dosemu clobber COM4?

Rob Janssen rob@pe1chl.ampr.org reported (94/3/24) that:

According to jmorriso@bogomips.ee.ubc.ca, "dosemu still clobbers COM4 (0x2e8, IRQ 5). 0x2e8 isn't in ports{} in config. I have to run setserial /dev/ttyS3 irq 5 on it after dosemu exits."

This is caused by your VGA BIOS. I have found that by enabling the IO port trace and seeing where it was clobbered.

Disable some ports in config and it will work fine. When you then have problems with the video, try to enable more selective ranges of IO addresses (e.g., 40-43).

### How do I use dosemu over the serial ports?

### How can I switch between dosemu and a shell over the serial line?

John Taylor taylor@pollux.cs.uga.edu reported (94/5/25) that:

I am running Linux 1.1.13 and want to point out a great feature that should be protected and not taken out (IMHO). With the 52 version, I can run the program, "screen." From screen, i can invoke dosemu -D-a. What is really great (IMHO) is the screen commands (the CTRL-A cmds) still work. This means I can do a CTRL-A C and add another unix shell, and switch between the two (DOS / UNIX). This allows me to use dosemu over the serial line really well, because switching is made easy.

You may also consider using `dosemu -dumb`. In this case the escape sequences from the DOS applications go directly to the terminal.

### How can I get the parallel ports to work?

The dosemu.conf has lines at the end to redirect printers to either lpr or a file. If you want direct access to the bare metal, comment out these emulation lines, and add the line:

    $_ports = "device /dev/lp0 fast range 0x3bc 0x3bf" # lpt0

for the "monitor card" printer port (corresponds to /dev/lp0), or:

    $_ports = "device /dev/lp1 fast range 0x378 0x37f" # lpt1

or:

    $_ports = "device /dev/lp1 fast range 0x278 0x27f" # lpt2

for LPT1 (/dev/lp1) or LPT2 (/dev/lp2) respectively(97/2/9).

Hans Lermen lermen@dosemu.org writes:

But NOTE: these lines should not be _added_ simply, the string should be concatenated such as:

    $_ports = "...."
    $_ports = $_ports, " device /dev/lp0 fast range 0x3bc 0x3bf"
    =
    This blank is important

Note: newer kernels don't have hardcoded dependencies between `/dev/lp*` and ioports. Check `/proc/ioports` for lines such as `0378-037a : parport0`.

## Multiple users and Non-interactive sessions

### Can I use dosemu on a multi-user system?

Yes, you can configure dosemu on a per-user basis. See README.txt for details.

### How can I run dos commands non-interactively?

You can do any of the following:

1. use the keystroke configuration option and the -input command line option as described in the manual page to specify keystrokes on the command line that will act exactly as if you had typed them within dosemu.

2. Use the `dosemu [-E] dos-command` and `unix -e` as your last line in `autoexec.bat`. The specified dos command is executed. If '-E' is not given, then DOSEMU exits after running the command.

Here are some additional alternatives:

Daniel T. Schwager danny@dragon.s.bawue.de reported (94/7/2) that:

You can use different dosemu.conf files (and different hd-boot-images with different autoexec.bat's) and call dosemu like:

    $ dosemu -f my_quicken_q_exe_dosemu.conf

---------------------

Dietmar Braun braun@math20.mathematik.uni-bielefeld.de reported (94/7/4) that:

This is no problem at all when you use the redirector of dosemu. It is possible to redirect a drive letter to a linux path given by an environment variable.

So I have a shell script named "DOS" which does something like:

    mkdir /tmp/dos.$$
    DOSTMP=/tmp/dos.$$; export DOSTMP

and then a little trick to get "echo $* > $DOSTMP/startup.bat" really working (actually a small C Program which turns `/' in `\' and terminates lines correctly for messy dos with cr/lf pairs and adds `^Z` at the end of the file), creates startup files, links and so on in this directory, and then starts dosemu. Within "`autoexec.bat`" drive c: is redirected from hdimage to this tmp-directory, which has links for `$HOME` and `$PWD`.

So if I want to see my filenames shortened to 8.3 I can type "DOS dir" and I get my current directory listing. So I have full DOS multi user (I don't have any DOS partition and redirecting to Linux preserves user permissions) and multi tasking. (dosemu sessions are completely independent). I did this once to be able to use a dos driver for my printer. My printcap df is actually a DOS program. So you can even make DOS executables act as lpr filters.

## dosemu and Netware

### How do I get Netware access from dosemu?

As always, access through the Linux filesystem is preferred. Mount your Netware drives with Caldera's Netware utilities or Volker Lendecke's free ncpfs utility ftp://ftp.gwdg.de:/pub/linux/misc/ncpfs. If you need real IPX access, e.g. to run Novell's "syscon", read `doc/NOVELL-HOWTO.txt`. You probably can not currently access Netware from FreeDOS.

## dosemu and X-windows(97/2/9).

### How do I obtain fullscreen mode in xdosemu?

Toggle between windowed and fullscreen mode using Ctrl-Alt-F.

### Can I run dosemu in console mode while running X?

Ronald Schalk R.Schalk@uci.kun.nl reported (94/1/17) that:

Yes, no problem. Just remember to use ctrl-alt-<Fn> to go to a Virtual Console (VC), and you can run any Linux application (dosemu is a linux-application). I've got almost always WP5.1 in a dos session.

`[`Note: Use ctrl-alt-F7 to switch back to X from dosemu, if X runs on VC7.`]`

### Is it possible to run dosemu in a window in X-windows?

If you have X installed and you have successfully compiled dosemu and run it successfully outside X-windows, you should be able to run xdosemu or `dosemu -X` right away to bring up a dosemu window. If this does not work, make sure:

1. Dosemu has X support compiled in. This is default, however if you you have compiled dosemu with "x off" in the compiletime-settings file you don't have X support. So changing "x off" to "x on" in the compiletime-settings file, followed by "make pristine; make; make install" should build you a dosemu-executable with X support, if you have the X-libraries installed in `/usr/X11R6`.

2. You might need to fix backspace and delete; but nowadays this is rarely necessary. In that case, set up your X key-mappings. In an xterm, type `xmodmap -e "keycode 22 = 0xff08"`, and then `xmodmap -e "keycode 107 = 0xffff"`.

3. Configure the X-related configuration options in `~/.dosemurc`.

Alternatively, you can run dosemu inside a color xterm, which is not recommended because many color xterms have buggy support for the complex text display capabilities of dosemu. This does not require `X_SUPPORT` to be compiled into dosemu. However, if you really want to do this, do the following steps:

1. If necessary set up your X key-mappings as explained above.

2. Configure the terminal-related (not X-related) settings in `~/.dosemurc`.

Marty Leisner leisner@sdsp.mc.xerox.com reported (95/3/31) that:

I have xrdb log the following resources

    dosxterm*Font:  vga
    dosxterm*geometry:      80x25
    dosxterm*saveLines: 25

or I alias `dosxterm` to `term -fn vga -title dosxterm -geometry 80x25 -sl 25`.

If you use the xrdb method, all you have to do is run `xterm -name dosxterm`.

### Xdosemu does not work on a remote X-display!

At present, dosemu is set up to use the MIT shared memory extensions. This extension only works on a local display. If you want to run xdosemu on a remote display, you might need to set `$_X_mitshm=(off)` in your `dosemu.conf` or `.dosemurc`.

### Xdosemu does not find the VGA font

Check that the vga fonts you installed are listed in the font.dir of the directory you installed the fonts in:

    hertz:~> grep misc /usr/X11R6/lib/X11/XF86Config
    FontPath    "/usr/X11R6/lib/X11/fonts/misc/"
    hertz:~> grep vga /usr/X11R6/lib/X11/fonts/misc/fonts.dir
    vga.pcf vga
    vga11x19.pcf vga11x19
    hertz:~> ls /usr/X11R6/lib/X11/fonts/misc/vga*
    /usr/X11R6/lib/X11/fonts/misc/vga.pcf
    /usr/X11R6/lib/X11/fonts/misc/vga11x19.bdf
    /usr/X11R6/lib/X11/fonts/misc/vga11x19.pcf

If you installed some X-fonts, like you did when you installed dosemu with X-Support for the first time, "mkfontdir" and then "xset fp rehash" needs to be run. The dosemu install should take care for "mkfontdir" and tells you about "xset fp rehash". Tell us if it doesn't work for you. (97/2/13)

### The vga font is very small on my high resolution display

Set `$_X_font="vga11x19"`.

### Dosemu compilation fails with some strange error regarding X!

As stated above, dosemu uses the MIT shared memory extensions by default. Under XFree86 they are only available with Version 3.1.2 and above. If you have an older version, consider to upgrade, or configure dosemu to not use this extension by setting `mitshm off` in `compiletime-settings` (97/2/9).

### Does ansi emulation work properly?

Marty Leisner leisner@sdsp.mc.xerox.com reported (95/3/31) that:

Yes. I use `nnansi.com` under X windows. I find 25, 43 and 50 line mode work properly, however 50 line mode is difficult to use on a 1024x768 screen (unless smaller fonts are used or you use a bigger screen. 43 line mode will resize the `xterm` window to use 43 lines.

`DEVICE=c:\bin\nansi.sys` in FreeDOS' `config.sys` works too, except in "dumb" mode.

## dosemu and MS-Windows 3.x

### Is it possible to run MS-Windows 3.x under dosemu?

Yes, versions up to and including Windows for Workgroups 3.11 are currently working, but only under DOSEMU+MSDOS (not FreeDOS).

### Can I run 32bit stuff in Windows?

Sorry, no you can't. Win32s is not supported yet, Win9x is neither.

### Can I run Windows 3.x in xdosemu

Yes, this is similar to using it in DOSEMU on the console; the only extra thing to consider here is that the emulated graphics card in xdosemu is a Trident, which is most likely different from your real graphics card. The mouse also needs some special attention.

Hints:

1. For faster graphics (256 colors instead of 16 is faster in xdosemu), get the Trident SVGA drivers for Windows. The files are tvgaw31a.zip and/or tvgaw31b.zip. They are available at garbo.uwasa.fi in /windows/drivers (any mirrors?).

2. Unpack the Trident drivers.

3. In Windows setup, install the Trident "800x600 256 color for 512K boards" driver.

4. Start xdosemu.

5. In Dosemu, start windows.

### Can I install windows from within dosemu?

Yes, up to and including Windows For Workgroups 3.11.

#### Notes for the mouse under win3.x-in-xdosemu:

1. In order to let the mouse properly work you need the following in your `win.ini` file:

       [windows]
       MouseThreshold1=0
       MouseThreshold2=0
       MouseSpeed=0

2. The mouse cursor gets not painted by X, but by windows itself, so it depends on the refresh rate how often it gets updated, though the mouse coordinates movement itself will not get delayed. In fact you have 2 cursors, but the X-cursor is given an `invisible' cursor shape while within the DOS-Box.

3. Because the coordinates passed to windows are interpreted relatively, we need to calibrate the cursor. This is done automatically whenever you enter the DOS-Box window: The cursor gets forced to 0,0 and then back to its right coordinates. Hence, if you want to re-calibrate the cursor, just move the cursor outside and then inside the DOS-Box again. (97/2/10)

## Video and sound

### Can I run 32-bit video games under dosemu?

Mark Rejhon mdrejhon@magi.com reported (95/4/8) that:

You can run many 32-bit video games in dosemu. If the game is compatible in an OS/2 DOS box, there are chances that it will work in dosemu. (Example 32-bit games include Descent, Dark Forces, Mortal Kombat 2, Rise of The Triad, which have all successfully been tested in recent dosemu releases).

Before you attempt to run a video game on the console, you must have the keyboard configured in raw keyboard mode, and enabled VGA graphics modes, in `dosemu.conf` or run `dosemu -s`. Moreover you must run DOSEMU as root, execute it via sudo or make `dosemu.bin` suid root.

Alternatively try running the game in xdosemu; press Ctrl-Alt-F to toggle fullscreen mode. Root permissions are unneeded and in almost all cases no configuration is necessary, but the speed may be slower than on the console, and a few games still exhibit glitches. Use `speed 0` or some high value instead of 0 at the DOS prompt to temporarily set your HogThreshold to run DOSEMU at full tilt. After exiting the game use `speed 1` or exit DOSEMU to give the CPU some rest.

Note that game timers can be a little bit slow, due to Linux multitasking and lack of high-frequency timer support. So the games may run from anywhere from 5 to 100 percent speed. Typically, the speed is approximately 50 percent in recent dosemu releases and is expected to improve eventually.

Who knows, it might even work. If you can't get it to work, check EMUfailure.txt if the program is listed there, or falls in a category of programs that at present don't or probably never work with dosemu. If you think, it should be listed in `EMUfailure.txt`, report to linux-msdos@vger.kernel.org.

### Exiting from dosemu on the console gives me a screen full of garbage.

(95/4/8) The problem is that the font information for the VGA text screen is not being saved. Get a copy of the svgalib package. The current source is in:

    ibiblio.org:/pub/Linux/libs/graphics/svgalib-1.4.3.tar.gz

It may also be available as a pre-compiled package in your favorite Linux distribution (e.g., Slackware, etc.). Use `savetextmode` to save the current text mode and font to a file in `/tmp` before running dosemu. Then run `textmode` upon exiting dosemu to restore it.

Addition from lermen@elserv.ffm.fgan.de (97/2/11):

Have a look also at `README-tech.txt`, where it is explained how dosdebug can aid you recovering.

If you use a graphical framebuffer console (but not vesafb) then `/usr/sbin/fbset "1400x1050-60"` or whatever your normal resolution and frequency are may help.

### Why doesn't my soundcard software work with dosemu?

Dosemu includes a Sound Blaster 16 emulator called SBemu. See sound-usage.txt for information on setting this up. It may not work for everything. Programs that are known to work are Impulse Tracker and most games. One that is known not to work well is FastTracker II.

If you have trouble getting sound to work at all, make sure you have a working OSS driver and have configured everything properly as described in sound-usage.txt. If most of your sound software works but some programs don't detect sound, make sure your BLASTER environment variable is set properly. Finally, make sure you are aware of the difference between digital sound, FM, and MIDI; it may be, for example, that you have digital sound working but MIDI isn't set up properly.

If you believe DOSEMU really is having trouble with a specific program, and it isn't a configuration error on your part, then please, submit a bug report! Have a look at sound-usage.txt for information on getting debugging output.

## Problems and fixes

### Security issues

A full featured Dosemu needs to be suid root, e.g to access ports. Most dos programs don't need this however so when running under X you usually do not need to run dosemu as root. Dosemu runs as suid "root" only at the initialization stage, and drops this right thereafter, except in a forked "port server" (where necessary). But with DPMI, the Dos client program can access the whole user space, hence also can modify the dosemu code itself. This cannot lead to privilege elevation but may crash DOSEMU. There are several other important security considerations discussed in the Security section of `README.txt`.

### dosemu says "ERROR: general protection" and terminates when I run some program

This will happen if your program uses DPMI and you do not have DPMI enabled. Try changing the line:

    $_dpmi = (off)

in `dosemu.conf` to:

    $_dpmi = (nnnn)

where `nnnn` is the number of kilobytes of memory you wish to give to the DOS program (e.g. Doom requires about 4000 kilobytes).

Another likely cause is that your program uses VCPI (see `EMUfailure.txt` for more details) or some other means of switching to protected mode (other than DPMI), in which case it will never work under dosemu.

If none of these is the case, see FailureNotInEmufailure.

### Dosemu dies when booting. I have Win95 installed.

Dosemu relies that the Dos-Version on the hdimage and the Drive you map to contain command.com are the same. If not, dosemu will crash sooner or later. With the dual boot option Win95 offers when pressing the F4, F5 and F8 keys with the "Starting Win95" text, versions on the Win95 drive may swap. Take special care for command.com. Let your shell variable in config.emu point to the correct static version of command.com, e.g.: `shell=c:\win95\command.com c:\ /P /E:1024` (97/02/28)

### Dosemu hangs! How can I kill it?

Switch to another console and type dosdebug, then type kill (it may take a while but will work eventually).

### Dosemu crashed and now I can't type anything.

Daniel Barlow jo95004@sable.ox.ac.uk reported (95/4/8) that:

If you have no terminal or network access that you can use to log in, you may have to press the reset button. If you can still get a usable shell somehow, run `kbd_mode -a` to switch the keyboard out of raw mode, and/or `stty sane` on the console so that you can see what you're typing.

A useful thing to do is to use a script to run dosemu, and run `kbd_mode -a` automatically right after dosemu. When dosemu crashes, the script usually will resume running, and execute `kbd_mode -a`.

Alternatively, if the magic SysRq key is enabled in the Linux kernel, you can use Alt-SysRq-r to switch to xlate mode, and use Alt-Fn to switch to any other console (including X, if your screen display is thoroughly broken).

### I've enabled EMS memory in dosemu.conf but it does not help.

Rob Janssen rob@pe1chl.ampr.org reported (94/7/11): Don't forget to load the provided `ems.sys` from `config.sys`.

### How do I get rid of all those annoying "disk change" messages?

(94/8/11) Grab and install klogd. Try:

    ibiblio.org:/pub/Linux/system/Daemons/sysklogd1.2.tgz

### Why won't dosemu run a second time after exiting in console mode?

Aldy Hernandez aldy@sauron.cc.andrews.edu reported (94/7/8): You should disable your video and/or BIOS caching.

### Why will dosemu run in a term but not in the console?

JyiJiin Luo jjluo@casbah.acns.nwu.edu reported (94/4/19): I experienced exactly the same problem before. I figured out all the video shadow in my AMI BIOS must be disabled. Now dosemu runs fine on my system.

### How can I speed up dosemu?

In some cases it is useful to play with the value of the `HogThreshold` variable in your `dosemu.conf` file.

Daniel Barlow jo95004@sable.ox.ac.uk reported (95/4/8): `HogThreshold` should now be set to approximately half of the BogoMips value that the system reports on boot.

### How do I see debugging output?

Daniel Barlow jo95004@sable.ox.ac.uk reported (95/4/8): As of dosemu 0.60, debugging output is redirected to a file specified on the command line. Use `dosemu -D+a -o /tmp/debug` to log all debug output to `/tmp/debug`. There should no longer be any need to redirect `stderr`.

### Why are my keystrokes echoed ttwwiiccee??

Nick Holloway alfie@dcs.warwick.ac.uk reported (94/2/22) that:

After running dos after playing with some stty settings, I was getting doubled key presses. I can now reveal what the reason is!

It only happens when dos is run on the console with `istrip' set. This is (I think) because the raw scancodes are mutilated by the `istrip', so that key release events look like key press events.

So, the input processing needs to be turned off when using the scan codes on a console (it wouldn't be a good idea to do it for tty lines).

### Dosemu scrambles my screen?

For those graphics cards not fully supported in dosemu, with allowed console graphics a dosemu crash may leave your console in a scrambles and nearly unusable way. To prepare for that situation, Spudgun spudgun@earthlight.co.nz posted the following solution. First save your registers when running on the console ~> cat /usr/bin/savetextmode ~> restoretextmode -w /etc/textregs ~> restorefont -w /etc/fontdata Then, when a crash happened, run following script: restoretextmode -r /etc/textregs restorefont -r /etc/fontdata restorepalette

If it doesn't fix it nothing will! I also found having an X server running sometimes put my Vid card's registers into a strange state where this script made things worse I think since changing X servers and/or running savetextmode on a vt while X was running helped. (97/04/08)

### MS FoxPro 2.6 won't run

FoxPro 2.6 doesn't run on network drives. Alexey Naidyonov growler@growler.tsu.tula.ru states on that problem: And I guess your FoxPro files are on lredir'ed disk, yeah? The matter is that FoxPro doesn't run on such disk, but when I said $_hdimage="/dev/hda? ..." in `dosemu.conf`, it runs.

## Contributing to the dosemu project

### Who is responsible for dosemu?

Dosemu is built upon the work of Matthias Lautner and Robert Sanders. Bart Oldeman bart@dosemu.org is responsible for organizing the latest releases of dosemu.

    History of dosemu
    Version    Date                Person
    -------------------------------------------------
    0.1        September 3, 1992   Matthias Lautner
    0.2        September 13, 1992  Matthias Lautner
    0.3        ???                 Matthias Lautner
    0.4        November 26, 1992   Matthias Lautner
    0.47       January 27, 1993    Robert Sanders
    0.47.7     February 5, 1993    Robert Sanders
    0.48       February 16, 1993   Robert Sanders
    0.48pl1    February 18, 1993   Robert Sanders
    0.49       May 20, 1993        Robert Sanders
    0.49pl2    November 18, 1993   James MacLean
    0.49pl3    November 30, 1993   James MacLean
    0.49pl3.3  December 3, 1993    James MacLean
    0.50       March 4, 1994       James MacLean
    0.50pl1    March 18, 1994      James MacLean
    0.52       June 16, 1994       James MacLean
    0.60       April 9, 1995       James MacLean
    0.64.4     February 9,1997     Hans Lermen
    0.66.3     April 20, 1997      Hans Lermen
    0.98.1     December 9, 1998    Hans Lermen
    0.98.6     March 21, 1999      Hans Lermen
    1.0.0      March 6, 2000       Hans Lermen
    1.2.0      January 18, 2004    Bart Oldeman
    1.4.0      May 5, 2007         Bart Oldeman

### I want to help. Who should I contact?

Please join the linux-msdos and dosemu-devel lists; see http://www.dosemu.org/mailinglist.html for more information.