Installing SCO Unix 4.2, part 3: LBA disks

This is a guest post by Friggigatto

In the previous post we managed to install a Compaq-branded version of SCO Open Desktop. One of the recommendations was to use a small hard drive and avoid LBA, since SCO Unix does not recognize it.

It turns out, however, that SLS UOD429A, the bootdisk + patch that we used in the first post of this series to install ODT, also adds LBA support (as found out on A.P. Lawrence’s excellent website).

Apart from enabling you to fully use larger disks (you can install on a disk larger than 2048 cylinders, as long as you set its size to 2048 cyls during installation; you are of course going to “waste” a lot of space), LBA is more convenient if you want to have a large root partition, since the root partition has to be entirely in the first 1024 cyls.

So of course I tried repeating the installation of the Compaq version by booting off UOD429A, inserting the N2 from SCO ODT, and… I quickly found out that it would not recognize the CD as a valid installation media. Annoying.

Eventually I found out that the N1 disk from Compaq has a ramdrive compressed in the kernel, from where the initial installation script is run, while the rest of the files (mostly installscript) are on the CD itself.

The fix was, in the end, relatively simple. All I needed to do was mounting the N2 floppy in the VM I had created before, copying “N2.Z” on my harddrive. I then uncompress-ed it, extracted it (it’s a regular tar file), and replaced the installation script with the one provided on Compaq’s CD. Then, the reverse process can be done: recreate the “N2” tar file, compress it, and copy it in the mounted N2 disk. If you don’t want to go through the same process again, you can download the patched disk.

The installation process is then simple: boot off UOD429A, insert the updated N2 disk when requested, and proceed with the rest of the installation as usual.

This way I managed to install SCO Unix on a TI TravelMate 6050, alongside DOS and Windows 95. It took a bit of trial and error (reading SCO technical support documents was, again, very helpful), but in the end this is more or less what I did:

  1. install Unix as LBA with a ~20mb DOS partition
  2. hide DOS partition & create a new one as primary active partition
  3. install Win95 on that
  4. install boot manager (I used Paragon’s Boot Magic) on first DOS partition (the hidden one)

Steps 1 and 2 were done in 86box, after creating a disk with the same cylinders, heads and sectors found in the BIOS of my TravelMate (using the LBA setting in the BIOS of both laptop and emulated machine, of course). After installing DOS and SCO Unix (I’m not sure anymore in which order), I copied the Win95 installation files on the new partition and finished the installation process on the laptop, after dd-ing the image to the CF card I’m using as hard drive.

After configuring Boot Magic (and creating a custom background and icon), now I’m greeted with this every time I boot up the laptop:

Since Windows 95 is installed in a FAT16 partition, I can mount it or access it via dosls/doscp inside SCO Unix too, which is convenient for sharing files (I tried installing a 3Com 3C589 PCMCIA card directly in Unix, since according to the docs it’s supported; unfortunately, the provided drivers only work with IBM PCMCIA controllers).

SCO Unix software

A large collection of ports for SCO Unix can be found at, but it’s faster to use the ISO with all the ports I uploaded on
To mount the CD with lowercase filenames, run #mount -rf HS /dev/cd0 /mnt

It’s worth noting that, before using the CD, we need to install it with mkdev cdrom (yes, even if we did install the whole system from a CD). In the process we will be asked whether we want a CD-ROM/TAPE device, which can be used to install more components for the system (CD-ROM/TAPE is the format used by the setup CD), and if we want to add to the kernel ISO9660 support, which of course we need. As usual, SCO documentation has a lot of information about this.

Gzip is included in the Celestial ports, but I also managed to compile an early version of bzip2 (here is the binary). If you compile it yourself use gcc, the code will be faster. The provided Makefile undefines __STDC__; gcc sets the flag and this creates problems at linking time, resulting in a call to a missing “__unlink” function.

Bonus content: recovery disks

In the process of getting more familiar with the installation process of SCO Unix, I realized I could benefit from having a set of spare bootdisks that would allow me to mount the hard drive and modify files at will (including after the first part of the installation process). So, I created them, using a ramdrive + compressed disk (similar to what SCO’s install process does, but also the boot floppy of Windows 98) to pack as many utilities as possible on a single disk.While I was at it, I did the same for Xenix 386.

Installing SCO Unix 4.2, part 2: the devsys

This is a guest post by Friggigatto

In the previous post we saw how to install SCO Unix 4.2 and SCO ODT on a virtual machine. Sadly, both distributions lack the development system, making them a very limited toy.

At some point I noticed that the filesize of the ISO of SCO ODT 3.0 branded by Compaq (found again on the Internet Archive or WinWorld) is way larger than the other available distributions: could it be that it includes the Development System as well? I decided to find out.

Inside the ISO we can find a N1.IMG file, and we can start the installation by booting from that.

At the serial request I discovered that this version is not the same as regular ODT, and thus the serials I had did not work. I tried extracting a to-be-serialized file from inside the CD.IMG file found on the ISO by opening it with a hex editor (the file is not in ISO9660 format; it’s specific to SCO and somewhat emulates a tape drive, with multiple tar files in it. Opening it with a hex editor, it’s easy to see where one of these tar files starts and ends), extracting it with tar, and running it through brandy to generate a new serial.

Brandy, however, generated the same serials/activation I had already, indicating that the validation mechanism used by the installer in this release is different. I was afraid it would be a Compaq-specific addition, thus almost unrecoverable, but after searching Usenet I found this post (mirror) which suggests that different versions of ODT have different generation mechanisms; in any case, the keys provided in the “OSE” (Open Server Enterprise) column work.

Anyway, after inserting the serial the installation proceeds smoothly, and we can even select to install the Development System:

The DevSys also requires a serial, and for that I used one found on the archive of Tenox. The installation started with the incredibly slow process of badtracking the hard disk (and I had selected the “quick” check!) and proceeded smoothly, until it tried to install the “Compaq EFS for SCO Unix”:

The error interrupts the installation scripts and leaves the system in a half-baked state: we can reboot from the HD and load the kernel, but instead of getting to a terminal or login prompt we are dropped in a broken installation script that won’t proceed.

To fix the issue, I opened up again the ISO with a hex editor and looked at the install script (/inst5/customize). The fix is easy: search for the string “cleanup $FAIL” inside the CD (line 238 of the customize script), and replace the initial “c” with a “#” to comment out the line entirely (a neater solution would be to change the script so that it won’t install the Compaq EFS in the first place; I tried to do that as well, but it didn’t work).
Since we are at it, we can also modify the params.stz file in the ISO and disable badtracking completely (search for badtrk_none) and speed up the next installation considerably.

Restarting the installation once again with the same settings will still give the error, but this time it won’t kill the installation script and it should now complete successfully (with some warning messages since it’s not an EISA machine).

After the reboot, we should be finally welcomed into “SCO Open Server (From Compaq) Enterprise System Release 3.0”.

We can now remove the whole Compaq EFS using custom, or just the UPS drivers /etc/rc.0d/*ups and /etc/rc2.d/*ups, in addition to /usr/bin/compaq. We can also apply the patch to the disk driver to run on faster machines, as mentioned in the previous post. Finally, we can install SCO supplements from SCO’s FTP, and in particular:

  • uod426d – Y2k fix;
  • uod374a – better CD support (you can run programs from ISO-9660 CDs, for example from early SCO Skunkware releases; you can also mount CDs forcing each name to lowercase, instead of the annoying default where everything is in uppercase);
  • net382e – better TCP/IP support.

Now we have a working SCO Unix 4.2 system with the development system! The good thing about SCO Unix is that the C compiler is more modern than the one provided by SCO Xenix, but can still target Xenix (with the -l2.3 directive). This means we can compile slightly more recent software for both systems, for example bash 1.13.5 and bzip2 0.1pl2.

Continued in Part 3!

Installing SCO Unix, part 1

This is a guest post by Friggigatto

I’ve been messing around with SCO Xenix for about 10 years now, and in the process I have been playing with OpenServer 5/6 as well (mostly as a mean to copying big/many files to a Xenix VM: I’d just create an ISO file, mount that in OpenServer, then share the Xenix HD with OSR5 and copy the files over); however, I never got around to use SCO Unix.

A while ago I decided to change this, but it took many tries to get to install everything, especially the Development System; so, when I eventually managed, I decided to do a writeup of what I did (and part of what stumbling blocks I encountered along the way).This is the “first episode”, which should give you enough info to install SCO OpenDesktop 3.0 as found on WinWorld or on, and the ODT Server 3.0 version from BetaArchive. ODT is nothing else than SCO Unix 4.2 bundled with X11 and TCP/IP (while on Xenix these are separate products).

Installing SCO ODT, floppy version

The secret to installing the 4.2 floppy version was to use the updated N1 boot diskette (SLS uod429a from SCO). Once you have it, the installation process is quite straightforward and self-documenting, especially if you are used to the slightly more convoluted Xenix install. This version can even be installed in VMWare.

The serial/activation is included in the release files; create a VM with an hard drive <2gb, during the setup process select “Floppy” as the install media, a “quick” bad track scan type and then simply confirm every step. You will be asked to insert all the disks in order, and the only challenge should be surviving the mind-numbing boredom of handling more than 40 floppies.
Unfortunately, the network and graphics card are not supported on VMWare (I suggest to boot the first time in single-user mode and disable the GUI from starting automatically with “scologin disable”), so it’s a good idea to install on 86box instead.

While we are at it, we can even spare ourselves some of the boredom by using the CD version instead.

Installing SCO ODT, CD version

For the ODT CD version, I looked up at what SCSI devices are supported (mostly by running ‘strings’ on the kernel inside the boot floppy image, looking at the device driver names and comparing them with those of OpenServer 6), and created a machine on the latest unstable 86box build ( like this:

  • i486-socket 2 and 3: [i420EX] ASUS-PVI-486AP4 (many other boards work as well, but faster CPUs/machines would give me issues… more on this later)
  • Intel i486SX 33mhz + 487SX
  • 32 Mb RAM
  • Serial Logitech mouse, 3buttons
  • Video: ISA16 Orchid Farenheit 1280 [note for the setup: the emulated bios is 2.0 – supports 1024×[email protected] colors]
  • SCSI controller: aha-154xA
    Address 0x330, IRQ 11, DMA 5
    Host ID 0
    BIOS C800H
  • SCSI cdrom
    Controller 0, ID 5
  • IDE hard drive, <2Gb, non-LBA (check the BIOS settings)
  • If you want Ethernet, use WD8013EBT (drivers are included)
    IRQ3 address 240

The OpenServer release I found on BetaArchive was missing the N2 disk, but the one from the floppy release works fine. The process is simple: boot from N1, the SCSI adapter should be recognized by the kernel (a line that starts with “%adapter” and then the IRQ settings etc.), and so should be the disk drive (%disk):

You can use the same serial as for the floppy release, but this time indicate “SCSI CD-ROM” as the install media, and it should install fine. You should however deselect the DOS Services, as Unix will crash after the first reboot while trying to install them.

Once the installation is complete and the system restarted, it will greet you with this very dramatic login screen (and ironic too: SCO and Open Systems in the same logo) and its pastel-colored UI:

Running on faster machines

The 33 mhz CPU is surely not a beast by today’s standards, and the emulated system feels sluggish enough also under ODT; however, switching to a faster CPU would crash the system. Luckily, SCO’s former support website (I created a mirror of the tech articles on has a solution for this: we can modify a driver to avoid kernel panics on quick systems. After booting into single-user mode, we can run

# cd /etc/conf/pack.d/pit
# cp Driver.o Driver.orig
# _fst -w Driver.o
* spinwait+2D?w F989 FEE2
* $q
# cd /etc/conf/cf.d
# ./link_unix -y

Finally we can safely reboot, this time with a better CPU. The fastest machine I could test is a Socket 5 (i430NX Gigabyte GA-586IP) Pentium MMX Overdrive 200Mhz. When a faster system is selected (e.g. those based on Socket 7), the mouse stops registering the vertical axis.

In the next post, we’ll see how to install ODT with the development system.