Windows NT 4 on libvirt

Tech

To celebrate this month being the 30th anniversary of Windows NT 4.0’s release, I wanted to put together a little guide for how to get it up and running smoothly in libvirt on Linux.

I’ve personally had a world of hurt trying to get Windows NT Terminal Server to work at all with libvirt/qemu. Lots of disk corruption and I/O errors. This guide is only tested and working with with Workstation and regular Server.

Windows NT 4.0 Desktop

Create a new VM

When creating a new VM, libvirt won’t detect the OS from the install media.

  1. Open the search box
  2. Tick Include end of life operating systems
  3. Pick Windows NT Server 4.0 (winnt4.0)

I pick a disk size of 4 GB since the NT installer won’t let you format and install to a C: drive larger than 4 GB. You can always add more disks later.

128 MB of RAM is typically ample for NT.

At the last step, do not begin installation yet. We have a bunch of settings to change. Tick Customise configuration before install.

Drivers

This guide makes driver recommendations to get the best virtual NT 4.0 experience.

I’ve assembled a floppy disk image with all necessary drivers: qemu-nt4.img

Configuration

CPU

Disable Copy host CPU configuration. Set the model to pentium-v1.

Boot Options

Optional, but a quality of life change to make here.

The Windows NT installation CDs will always boot directly into the installer. There is no “press spacebar to install…” with a timeout like Windows 2000 and XP have.

To avoid having to eject and re-insert the virtual CD-ROM multiple times, make the hard drive have first boot priority. With a blank hard drive image, you’ll boot into the installer, and after the first phase, off the hard drive.

IDE cache mode

If you don’t change these settings, you’ll get random I/O errors during installation and VM usage that can be fatal.

For both IDE Disk 1 and IDE CDROM 1, under Advanced options, change the Cache mode to writethrough.

Network

You have two options when it comes to network cards in libvirt/qemu.

Windows NT 4.0 has built-in drivers for the pcnet network card. This is a 10 Mb card from AMD and works fine, but you’ll be limited to 10 Mbit which can be rough depending on what you use the VM for. You won’t find pcnet in the Device model dropdown, but you can type it in or edit the XML.

Your other option is the Realtek rtl8319. This is a 100 Mbit card that’s well-supported by NT 4, but you’ll need a driver floppy or CD-ROM to install it.

Sound

Windows NT 4 has built-in support for the Sound Blaster 16 card. You’ll have to edit the XML configuration to set use model and configure the ISA bus.

<sound model="sb16">
  <alias name="sound0"/>
  <address type="isa" iobase="0x220" irq="0x7"/>
</sound>

Video

There are multiple video card models that can work in NT and provide high resolution and high colour depth graphics.

  • vga - With the VirtualBox VBE Miniport driver or QEMU std-vga driver
  • vmvga - With the VMWare SVGA driver

The no-driver option is cirrus which will at least give you decent colour depth at low resolutions.

Optional: Floppy drive

If you want to install network support during setup, a floppy drive and image is the natural way to do this.

During setup

Display

  • DO NOT try to change the display settings at all. It’ll hang the VM and you’ll have to hard-reset and start the graphical portion of the install over again.

Post-install

Once your new NT install is up and running, there are few more things you’ll want to do.

ATA Driver

By default, your I/O will be running in PIO mode which is terribly slow. Unless you want your VM to feel like you’re running on a vintage 486, you’ll want to install an ATA driver so you’re running in DMA mode.

The UniATA driver works great and will provide a noticeable improvement in disk I/O performance.

In Control Panel, open up SCSI Adapters

Sound

If you’re using sound:

  1. Open up Control Panel, Multimedia, and the Devices tab.
  2. Click Add and then pick Creative Labs Sound Blaster 1.X, Pro, 16.
  3. On the Configuration screen, set the MPU401 I/O Address to Disable.

Video

Install the right drivers for your card. VMWare SVGA (for vmvga) and VirtualBox VBE Miniport for (vga) both work well.

I’ve found that vmvga can have some strange rendering issues like the mouse being too large and screen elements persisting. The VBE driver causes a license to appear during the blue startup screen, but that’s not a problem.

Service Pack 6

Once you’re done installing system components and drivers, upgrading to Service Pack 6 is a must.

You can also install the final updates:

  • Service Pack 6a
  • Post-SP6 update q299444

Wrapup

If all goes well, you should have a snappy NT 4.0 VM with all the essential hardware working nicely!

For bonus fun, you can add IPv6 support to your system.

Windows NT 4.0 Desktop

libvirt XML Sample

The stock/default config for things like SPICE and USB controllers has been removed from this to focus on the parts that matter.

<domain type="kvm">
  <metadata>
    <libosinfo:libosinfo xmlns:libosinfo="http://libosinfo.org/xmlns/libvirt/domain/1.0">
      <libosinfo:os id="http://microsoft.com/winnt/4.0"/>
    </libosinfo:libosinfo>
  </metadata>

  <memory>131072</memory>
  <currentMemory>131072</currentMemory>

  <!-- NT may BSOD if you change this to multi-processor. -->
  <vcpu>1</vcpu>

  <os>
    <type arch="x86_64" machine="pc-i440fx-10.0">hvm</type>
  </os>

  <!-- NT doesn't support ACPI, so you can remove the `<acpi>` element entirely -->
  <features>
    <apic/>
    <vmport state="off"/>
  </features>

  <!-- You may encounter BSOD if emulating newer processors -->
  <cpu mode="custom" match="exact">
    <model>pentium-v1</model>
  </cpu>

  <devices>
    <emulator>/usr/bin/qemu-system-x86_64</emulator>

    <!-- Make sure to set "writethrough" for the cache -->
    <disk type="file" device="disk">
      <driver name="qemu" type="qcow2" discard="unmap" cache="writethrough"/>
      <source file="/tank/vm/images/nt4w7.qcow2"/>
      <target dev="hda" bus="ide"/>
    </disk>

    <!-- Make sure to set "writethrough" for the cache -->
    <disk type="file" device="cdrom">
      <driver name="qemu" type="raw" cache="writethrough"/>
      <source file="/tank/library/virt/winnt40wks_sp1_en.iso"/>
      <target dev="hdb" bus="ide"/>
      <readonly/>
    </disk>

    <!-- Optional, but makes life easier to get drivers on the VM -->
    <disk type="file" device="floppy">
      <driver name="qemu" type="raw"/>
      <source file="/tank/library/virt/qemu-nt4.img"/>
      <target dev="fda" bus="fdc"/>
      <readonly/>
    </disk>

    <!-- You can also use `pcnet` for 10 Mbit -->
    <interface>
      <model type="rtl8139"/>
    </interface>

    <!-- Must be on the ISA bus to work -->
    <sound model="sb16">
      <alias name="sound0"/>
      <address type="isa" iobase="0x220" irq="0x7"/>
    </sound>

    <!-- Can also use `vmvga` with the VMWare drivers -->
    <video>
      <model type="vga"/>
    </video>
  </devices>
</domain>