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GXemul: Unsupported guest OSes

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NOTE: The guest operating systems listed on this page are here because they do not work well enough to be regarded as "stable"/supported. If they become stable, they'll be moved to the guest OS page.

This page contains instructions on how installation of guest OSes could potentially be done, once the emulation is stable/complete enough. In some cases, it contains notes about starting guest OSes that are not complete (i.e. just booting a kernel, not a full installation of a guest OS).

Also note that ALL modes on this page are legacy modes.


Read the following link if you want to know more about Mach in general: http://www-2.cs.cmu.edu/afs/cs/project/mach/public/www/mach.html

NOTE: Mach for DECstation requires some files (called 'startup' and 'emulator') which I haven't been able to find on the web. Without these, Mach will not get very far. These installation instructions are preliminary.


The following steps should let you experiment with running Mach for DECstation in the emulator:

  1. Download the pmax binary distribution for Mach 3.0:
    	7263343 bytes, md5 = f9d76c240a6e169921a1df99ad560cc0
  2. Extract the Mach kernel:
            tar xfvz pmax.tar.Z pmax_mach/special/mach.boot.MK83.STD+ANY
  3. Create an empty disk image:
    	dd if=/dev/zero of=disk.img bs=1 count=512 seek=400000000
  4. Load the contents of pmax.tar.Z onto the disk image. This is complicated, and should be described in more detail some time. For now, use your imagination. (For example using OpenBSD/pmax: disklabel -E rz1; newfs -O /dev/rz1a; mount /dev/rz1a /mnt; cd /mnt; download pmax.tar.Z using ftp; tar xzvf pmax.tar.Z; mv pmax_mach/* .; rmdir pmax_mach; mkdir mach_servers; cd mach_servers; cp ../etc/mach_init .; cp ../tests/test_service startup; dd if=/dev/zero of=paging_file bs=65536 count=400; cd /; sync; umount /mnt)

  5. Start the emulator with the following command:
    	gxemul -c 'put w 0x800990e0, 0' -c 'put w 0x80099144, 0' \
    	    -c 'put w 0x8004aae8, 0' -e 3max -X -d disk.img \

Earlier versions of GXemul had a configure option to enable better R3000 cache emulation, but since Mach was more or less the only thing that used it, I removed it. Today's version of GXemul can thus not boot mach.boot.MK83.STD+ANY straight off, it has to be patched to skip the cache detection.

The -c commands above patch the kernel to get past the cache detection. Thanks to Artur Bujdoso for these values.

TODO: Better instructions on how to create the old-style UFS disk image.

Redhat Linux for DECstation:


The following steps should let you run Redhat Linux for DECstation in GXemul:

  1. Download a kernel. David Muse' Debian-install kernel works fine:
  2. Download a root filesystem tree:
    	19486676 bytes, md5 = 5bcb725c90209479cd7ead8ad0c4a414
  3. Create a disk image which will contain the Redhat filesystem:
    	dd if=/dev/zero of=redhat_mips.img bs=1024 count=1 seek=2000000
  4. This is the tricky part: on redhat_mips.img, you need to create an MS-DOS (!) partition table, and then an ext2 partition. This is what Linux will then see as /dev/sda1.

    I recommend you run fdisk and mke2fs and untar the archive from within Debian/DECstation or Debian/CATS running inside the emulator. (Alternatively, if you are on a Linux host, you could use a loopback mount, or similar. This might require root access. See e.g. http://www.mega-tokyo.com/osfaq2/index.php/Disk%20Images%20Under%20Linux.)

    In order to actually boot the system you need to modify /etc/fstab. Change

    	/dev/root               /               nfs     defaults        1 1
    	#/dev/sdc1              /               ext2    defaults        1 1
    	none                    /proc           proc    defaults        0 0
    	none                    /dev/pts        devpts  mode=0622       0 0
    	#/dev/root              /               nfs     defaults        1 1
    	/dev/sda1               /               ext2    defaults        1 1
    	none                    /proc           proc    defaults        0 0
    	none                    /dev/pts        devpts  mode=0622       0 0
    (Note sda1 instead of sdc1.)

To boot Redhat linux from the disk image, use the following command line:

	gxemul -X -e3max -o "root=/dev/sda1 ro" -d redhat_mips.img vmlinux-2.4.31

If you need to boot into single user mode, change options to -o "root=/dev/sda1 rw init=/bin/sh".


OpenBSD/sgi can (almost) run in GXemul on an emulated O2 (SGI-IP32) with root on nfs.


NOTE: I haven't succeeded all the way with this yet, and this shows/triggers many bugs in the emulator, but some of it works.

GXemul does not yet emulate the AHC PCI SCSI controller in the O2. (I have mailed Adaptec several times, asking for documentation, but never received any reply.) OpenBSD/sgi can still run in the emulator, as long as it doesn't use SCSI. For a simple test with the ramdisk (install) kernel, try dowloading


and run gxemul -xeo2 bsd.rd.

It might also be possible to netboot. Another emulated machine must then be used as the nfs root server, and the emulated O2 machine must boot as a diskless client. Performing this setup is quite time consuming, but necessary:

  1. First of all, the "nfs server" machine must be set up. This needs to have a 800 MB /tftpboot partition. Install NetBSD/pmax 3.1 from CDROM. (Don't forget to add the extra partition!)

  2. Configure the nfs server machine to act as an nfs server. Start up the emulated DECstation:
    	gxemul -e 3max -d nbsd_pmax.img
    and enter the following commands as root inside the emulator:
    echo hostname=server >> /etc/rc.conf
    echo ifconfig_le0=\"inet\" >> /etc/rc.conf
    echo nameserver >> /etc/resolv.conf
    echo > /etc/mygate
    echo /tftpboot -maproot=root > /etc/exports
    echo rpcbind=YES >> /etc/rc.conf
    echo nfs_server=YES >> /etc/rc.conf
    echo mountd=YES >> /etc/rc.conf
    echo bootparamd=YES >> /etc/rc.conf
    printf "client root= \\\n swap=\n" > /etc/bootparams
    echo "10:20:30:00:00:10 client" > /etc/ethers
    echo client > /etc/hosts
  3. Start the DECstation emulation again, and enter the following commands to download the OpenBSD/sgi distribution:
    (NOTE: This takes quite some time, even if you have a fast network connection.)
    cd /tftpboot; ftp -i ftp.se.openbsd.org
    (log in as anonymous...)
    cd pub/OpenBSD/4.0/sgi
    mget b*tgz c*tgz e* g* m*
    for a in *.tgz; do echo $a; tar zxfp $a; done
    echo / nfs rw 0 0 > /tftpboot/etc/fstab
    rm *.tgz
    dd if=/dev/zero of=swap bs=1024 count=32768
  4. Download the OpenBSD/sgi GENERIC and RAMDISK kernels:
  5. Create a configuration file called config_client:
    !  Configuration file for running OpenBSD/sgi diskless with
    !  a NetBSD/pmax machine as the nfs server.
    !  This config file is for the client.
    	add_remote("localhost:12444")   ! the server
    	local_port(12445)               ! the client
    	name("client machine")
            ! load("bsd")
    ... and another configuration file for the server, config_server:
    	local_port(12444)               ! the server
    	add_remote("localhost:12445")   ! the client
    	name("nfs server")
  6. Boot the "nfs server" and the OpenBSD/sgi "client machine" as two separate emulator instances:
    	in one xterm:
    	gxemul @config_server
    	and then, in another xterm:
    	gxemul @config_client
  7. In the OpenBSD/sgi window, choose "s" (for Shell), and type:
    ifconfig mec0; route add default
    mount -v /mnt
    cd /mnt/dev; ./MAKEDEV all; cd /; umount /mnt
    You might want to log in as root on the server machine, and run tcpdump -lnvv or similar, to see that what the client machine actually does on the network. The MAKEDEV script takes almost forever, so be patient.

NOTE: Everything up to this point should work. However, the next step (in gray) doesn't actually work:

Once everything has been set up correctly, change bsd.rd in config_client to just bsd (the GENERIC kernel). It should now be possible to boot OpenBSD/sgi using the NetBSD/pmax nfs server. (When asked for "root device :" on the OpenBSD machine, enter mec0.)

But it doesn't work. Probably because GXemul's implementation of the mec (ethernet card used in the O2) is too much of a quick hack. For now, use the bsd.rd kernel, and (at every boot) type:

	s  (for Shell)
	ifconfig mec0; route add default
	mount -v /mnt
	cd /mnt; usr/sbin/chroot .
	sh etc/rc

This will not cause OpenBSD to be booted normally, but at least a few basic things will work. By the way, the emulator performs so poorly, that you will have time to fetch several cups of coffee for each of the steps above.


It is (almost) possible to install and run OpenBSD/arc on an emulated Acer PICA-61 in the emulator.

Earlier, I had this guest OS listed as officially working in the emulator, but for several reasons, it has been moved down here to the "informative-but-not-really-working" section.

  • The last OpenBSD/arc release was 2.3. This means that it is very old, it would not give a fair picture of what OpenBSD is (if you are just looking to find out what it is like), and it is not worth experimenting with it. See http://www.openbsd.org/arc.html for more information.
  • OpenBSD/arc was (if I understood things correctly) never really stable, even on real hardare. Problems with too small an interrupt stack. Bugs are triggered in the emulator that have to do with issues such as this.


Currently, I don't test for every release whether or not OpenBSD/arc can be installed. Releases prior to 0.3.7 (but probably not 0.3.7) should work. Anyway, here are the old installation instructions:

To install OpenBSD/arc onto an emulated harddisk image, follow these instructions:

  1. Create an empty harddisk image, which will be the root disk that OpenBSD installs itself onto:
    	dd if=/dev/zero of=obsd_arc.img bs=1024 count=1 seek=700000
  2. Download the entire arc directory from the ftp server: (approx. 75 MB)
    	wget -np -l 0 -r ftp://ftp.se.openbsd.org/pub/OpenBSD/2.3/arc/
  3. You now need to make an ISO image of the entire directory you downloaded. (I recommend using mkisofs for that purpose. If you don't already have mkisofs installed on your system, you need to install it in order to do this.)
    	mkisofs -o openbsd_arc_2.3.iso ftp.se.openbsd.org/pub/OpenBSD/
  4. Start the emulator using this command line:
    	gxemul -e pica -X -d obsd_arc.img -d b:openbsd_arc_2.3.iso -j 2.3/arc/bsd.rd
    and proceed like you would do if you were installing OpenBSD on a real Acer PICA-61. (Answer 'no' when asked if you want to configure networking, and then install from CD-ROM.)

Once the install has finished, the following command should let you boot from the harddisk image:

	gxemul -X -e pica -d obsd_arc.img ftp.se.openbsd.org/pub/OpenBSD/2.3/arc/bsd

The system is very sensitive to (I think) kernel stack overflow, so it crashes easily. If I remember correctly from mailing lists, this also happened on real hardware.

Debian GNU/Linux for CATS:

Debian GNU/Linux for CATS (ARM) could theoretically run in GXemul, however:
  • The DEC 21143 NIC is not emulated well enough for Linux to accept it.
  • Development of Debian for CATS seems to have died? The latest install kernel is quite old.


The following installation instructions would theoretically work:

  1. Create an empty harddisk image, which will be the root disk that Debian installs itself onto:
    	dd if=/dev/zero of=debian_cats.img bs=1024 count=1 seek=3300000
  2. Download the tftpboot install kernel:
  3. Start the installation using the following command line:
    	gxemul -XEcats -d debian_cats.img tftpboot.img

It doesn't work, though, because the NIC isn't working well enough.

The only use of Debian/CATS in the emulator right now is as a way to manipulate Linux disk images, if you are on a non-Linux host. By choosing "Execute a shell" in the installer's menu, you can have access to tools such as fdisk and mke2fs, which are useful for creating Linux paritions on disk images.

Linux/Malta (variant 1):

The Malta emulation mode is best suited for running NetBSD/evbmips, however, it is possible to experiment with Linux/Malta as well.

The general idea behind Linux/Malta seems to be that the end user always compiles his/her own kernel, applies patches, downloads userland separately, etc. For that reason, Linux/Malta support in the emulator is not tested for every release (sometimes it works, sometimes it doesn't work), and these instructions are kind of "fuzzy".

  1. Create an empty harddisk image, which will be the root disk that Linux/Malta will be installed onto:
    	dd if=/dev/zero of=linux.img bs=1024 count=1 seek=5000000
  2. Download a MIPS root filesystem tree:
    	19486676 bytes, md5 = 5bcb725c90209479cd7ead8ad0c4a414
    This is an old Redhat tree from 2001, but it seems to almost work.

  3. Download one precompiled Malta kernel, with ramdisk, and one without ramdisk (which will be used later on when booting from disk):
  4. Start the emulator with the ramdisk kernel, create a MS-DOS style MBR on the disk, create the filesystem, and extract the userland files:
    	gunzip vmlinux_2.*
    	gunzip mipsel-root-20011216.tar
    	gxemul -xemalta -d linux.img -d mipsel-root-20011216.tar vmlinux_2.4.33.2-ide-pci-ramdisk.elf
    	Inside GXemul: Log in as root and execute the following commands:
    	fdisk /dev/hda
    	(enter suitable commands, e.g. n, p, 1, 1, 9921, w)
    	mkfs /dev/hda1
    	mount /dev/hda1 /mnt
    	cd /mnt; tar -xf /dev/hdb; cd ..
    	umount /mnt; sync; reboot

It should now be possible to boot from the disk image, using the following command:

	gxemul -xemalta -d linux.img -o "root=/dev/hda1 rw" vmlinux_2.6.18-rc4-ide-pci-novty.elf

There's a slight problem with this specific Redhat tree, so when you see the message "Configuring kernel parameters: [ OK ]", press CTRL-C once.

Linux/Malta (variant 2):

The Malta emulation mode is best suited for running NetBSD/evbmips, however, it is possible to experiment with Linux/Malta as well.

It is also possible to experiment with much newer Linux userland, compared to the Linux/Malta variant 1 above, by using a kernel and disk image from http://people.debian.org/~aurel32/qemu/mipsel/. THIS DOES NOT WORK YET!

  1. Download the Malta kernel and disk image:
    	wget http://people.debian.org/~aurel32/qemu/mipsel/vmlinux-2.6.26-1-4kc-malta
    	wget http://people.debian.org/~aurel32/qemu/mipsel/debian_lenny_mipsel_small.qcow.gz (142 MB)
  2. The disk image is both compressed and in QEMU format, so we need to extract it:
    	gunzip debian_lenny_mipsel_small.qcow.gz
    	qemu-img convert -f qcow -O raw debian_lenny_mipsel_small.qcow debian_lenny_mipsel_small.raw
    (qemu-img actually requires that you have QEMU installed.)

It should now be possible to boot from the disk image, using the following command:

	gxemul -e malta -d debian_lenny_mipsel_small.raw -o "root=/dev/hda1 console=ttyS0" vmlinux-2.6.26-1-4kc-malta


I've added a machine mode which emulates the MIPS machine mode used in Fabrice Bellard's QEMU. Starting with QEMU 0.9.0, there are other MIPS modes in QEMU (i.e. Malta); the QEMU_MIPS mode in GXemul refers to the old QEMU-specific MIPS machine.

The following steps should let you boot into the Linux/QEMU_MIPS kernel, in way similar to the run-qemu script:

  1. Download the archive from http://wiki.qemu.org/Download and extract it:
    	wget http://wiki.qemu.org/download/mips-test-0.2.tar.gz
    	tar zxvf mips-test-0.2.tar.gz
  2. Start GXemul using the following command line:
    	gxemul -E qemu_mips -x -M 128 -o 'console=ttyS0
    		rd_start=0x80800000 rd_size=10000000 init=/bin/sh'
    		0x80800000:mips-test/initrd.gz mips-test/vmlinux-2.6.18-3-qemu

Windows NT/MIPS:

Old versions of Windows NT could run on MIPS hardware, e.g. the PICA 61. It is theoretically possible that the emulation provided by GXemul some day could be stable/complete enough to emulate such hardware well enough to fool Windows NT into thinking that it is running on a real machine. IT DOES NOT WORK YET!

Installation steps similar to these would be required to install Windows NT onto a disk image:

  1. Put a "Windows NT 4.0 for MIPS" CDROM (or similar) into your CDROM drive. (On FreeBSD systems, it is usually called /dev/cd0c or similar. Change that to whatever the CDROM is called on your system, or the name of a raw .iso image. I have tried this with the Swedish version, but it might work with other versions too.)

  2. Create an empty harddisk image, which will be the disk image that you will install Windows NT onto:
    	dd if=/dev/zero of=winnt_test.img bs=1024 count=1 seek=999000
  3. Run the ARC installer, to partition the disk image:
    	gxemul -X -e pica -d winnt_test.img -d bc6:/dev/cd0c -j MIPS\\ARCINST
    Note that ARCINST almost works, but not quite.

  4. Run the SETUP program:
    	gxemul -X -e pica -d winnt_test.img -d bc6:/dev/cd0c -j MIPS\\SETUPLDR

SETUPLDR manages to load some drivers from the cdrom, but then it crashes because of incomplete emulation of some hardware devices.


This doesn't work, and the playstation2 port of NetBSD is dead at the time of writing this.


To attempt to run the latest snapshot (from 2002):

  1. Download ftp://ftp.netbsd.org/pub/NetBSD/arch/playstation2/snapshot/20020327/binary/kernel/netbsd-GENERIC.gz and run
    	gxemul -X -E playstation2 netbsd-GENERIC.gz

Supplying a disk image with -d almost works. Then it hangs, waiting for keyboard input from a keyboard which doesn't exist.


This doesn't work yet. Starting point for development:

See http://wiki.netbsd.org/ports/evbarm/raspberry_pi/ for more info on NetBSD.

To start debugging/development:

  1. Download something similar to:
  2. gxemul -tviK -E rpi netbsd-RPI.gz

TODO: Everything.

GXemul> u
c00081e0:  e10f1000	mrs	r1,CPSR
c00081e4:  e166f001	msr	SPSR_sx,r1
c00081e8:  e28f1048	add	r1,pc,#0x48
c00081ec:  e8912106	ldmia	r1,{r1,r2,r8,sp}
c00081f0:  ee0d8f90	mcr	15,0,r8,cr13,cr0,4

It starts up in kernel_text, which is in NetBSD usr/src/sys/arch/arm/arm32/locore.S:


        mrs     r1, cpsr                /* fetch CPSR value */
        msr     spsr_sx, r1             /* set SPSR[23:8] to known value */

        adr     r1, .Lstart
        ldmia   r1, {r1, r2, r8, sp}    /* Set initial stack and */

        mcr     p15, 0, r8, c13, c0, 4
        ldr     r8, [r8, #L_CPU]        /* r8 needs curcpu in it */

        mov     r4, #0
        mov     r5, #0

Also useful for testing:

gxemul -tvK -E rpi 0x00000000:kernel.img
FreeBSD sd card image:
# Extract the kernel from the second (2) slice' first partition (a):
mdconfig -a -t vnode -f bsd-pi-250580M.img
mount /dev/md0s2a /mnt/
cp /mnt/boot/kernel/kernel* .
umount /mnt
mdconfig -d -u 0
gxemul -tK -E rpi kernel