Are you always up to date with the latest version of SCO’s operating system families? No? Don’t worry, you’re in the majority. According to SCO there are many older SCO UNIX and Open Desktop systems still running. There are even quite a few SCO XENIX systems running strong. The old adage "if it ain’t broke, don’t fix it" may work well with some things, but operating system technology has advanced considerably in the last few years. If you are running an older operating system version, there are a number of excellent arguments for upgrading. The upgrade may not be painless, but your system will run faster, be more flexible, and offer better security because of the effort you put in.

Instead of having only a single upgrade path to follow from SCO (Unix to OpenDesktop to OpenServer) we now have two diverging paths. You can upgrade to either OpenServer 5 or UnixWare 7, both excellent operating systems and both different from each other. While both operating systems will merge together to form a single product in the future, right now you can choose between the two to take advantage of each operating system’s strengths. Which should you choose? In this article we look at why you should upgrade, what’s involved in upgrading your existing system, and which operating system you should move to.

Why upgrade?

If you old system works just fine, why bother upgrading? There are a number of reasons, some of which may not be applicable to you. To start with, the later versions have much more efficient kernels and memory management routines. Whatever hardware you have, the OpenServer and UnixWare families can exploit better than older operating systems release while also incorporating more features.

Device support is greatly enhanced with later versions of SCO’s operating system family. Earlier versions of SCO UNIX had only a few devices that were compatible. Both OpenServer 5 and UnixWare 7 support practically every device on the market. For example, IDE drives are supported by both operating systems, making these inexpensive drives easy to use for both Desktop and Enterprise servers. Although you are limited to four IDE devices in two chains of two (one device usually is a CD-ROM), the development of IDE hard drives with almost 20GB of capacity make this a moot point. Eliminating the cost of a SCSI controller card and expensive SCSI hard disk devices can save more than the cost of the operating system upgrade alone! Network and video card support is increased enormously, allowing many Windows 95 compatible Plug-and-Play cards to work in your servers.

It’s the little things that make the difference, too. Instead of being limited to a 1GB root partition, it can be as big as you want. Security is beefed up enormously, both internally and on the user level. Integration with utilities has been an important point, allowing VisionFS and similar tools to work more effectively.

OpenServer vs UnixWare

SCO UnixWare 7 replaced the earlier UnixWare 2.1 which was essentially a repackaged Novell UnixWare release. Quite different from OpenServer in both underlying design philosophy and user interface, the choice between OpenServer and UnixWare rekindles the older BSD vs SVR4 debates to some extent. Neither is a "better" UNIX: they are different approaches to the same goal.

From a pure speed point of view, UnixWare 7 is a faster operating system than OpenServer 5. Under a load (such as Web or application server), UnixWare 7 can handle more requests per minute. The actual speed difference depends on the test conditions and loads, but varies from as little as 3% to over 10%. Performance differences are noticeable by end users when using X clients, with UnixWare running the faster of the two. UnixWare 7 makes better use of multiple processors and parallel SCSI chains than OpenServer.

OpenServer is a better operating system on underpowered machines. UnixWare requires more RAM, more disk space, and more CPU horsepower than OpenServer under identical conditions. If you are retaining your existing hardware and it is not sitting idle most of the time, UnixWare 7 will make any bottlenecks worse. Add in a problem with non-supported applications under UnixWare, and servers that run a lot of in-house OpenServer-specific applications should probably not upgrade to UnixWare.

Hardware issues

Earlier versions of SCO operating systems tended to require the operating system fit in the first 1024 cylinders of a disk (usually the first gigabyte). Additional filesystems had to be configured if you had a larger hard disk. The 1024 cylinder restriction has been removed with the latest versions of OpenServer and UnixWare, so you could configure a root partition as large as your hard disk, if you want.

If you are running on a small hard drive for your existing SCO Unix operating system, you may need to consider installing a larger first drive. Both OpenServer and UnixWare require about 250MB for an installation, so any disk smaller than half a gigabyte will be cramped (there’s a good chunk of disk real estate required for swap space, too). Hard disk prices are so low now that it makes sense to upgrade the disk drives when you upgrade operating systems.

There’s a new filesystem created by OpenServer and UnixWare when you install the operating system. This is the /stand filesystem, which holds up to three kernel images. The operating system boots from these images. Typically the /stand filesystem defaults to 15MB during the installation process, and it should not get any smaller than that. There is little benefit in making /stand any larger, though. If you are upgrading an older version of SCO UNIX you will have to make room for /stand filesystem. This may requires a backup-reformat-restore cycle. There is still no upper limit to the size of the hard drives supported. We regularly configure OpenServer and UnixWare on 9GB hard drives as a single, large filesystem (apart from /stand and the swap space).

Choosing the amount of swap space for your operating system can be tricky for those not experienced with OpenServer or UnixWare. As a rule of thumb, the absolute minimum swap space should be the amount of RAM in your system. (This is in case of a system crash, so the dump image can be comkpletely written to the swap space.) A more reasonable number to choose for your swap space size is 1.5 to 2 times the amount of RAM. If you support more than ten users, add about 10MB of swap space for each user over the tenth. Further, if you use large applications like databases, add even more. There are no real rules for how much swap space to add for databases and similar large applications, but at least the amount of physical RAM is a good bet. This means you can end up with some pretty large swap partitions, sometimes three to four times the amount of RAM. It’s not an issue to have too much swap space, but it does hurt system performance dramatically if you have too little. Neither OpenServer nor UnixWare care if the swap space is in a single large area or configured as several smaller areas, as long as the primary swap space is as large as the physical RAM.

Creating new swap space is a common problem for system administrators upgrading to OpenServer 5 or UnixWare. If your older system has a small swap space you need to increase the size when you migrate. Often this requires a back, format, and restore cycle of all your data. This is a time-consuming task but it is necessary.

CPU and RAM requirements for SCO OpenServer 5 and UnixWare depend to a large degree on your usage intentions. If you are not planning on supported a lot of remote X terminals, both operating systems will run quite happily on a slower Pentium with 32MB RAM. If you plan to use the GUI desktop locally and support X on terminals or PC clients, then you will require more RAM and more CPU horsepower. For a small network of ten PCs accessing the UNIX system through telnet or VisionFS, with two clients running X, 64MB RAM is a good starting point. Of course, the more memory the better. Considering the low cost of RAM, there’s no reason not to get more than enough.

Most systems being upgraded are single processor units. OpenServer and UnixWare both support multiple processors, so an upgrade to the hardware to allow present or future expansion to multiprocessing support may be logical for you if you find your CPUs are heavily used. There is no special software or configuration required when moving from single to multiple processors, other than linking in the proper kernel routines and rebooting. OpenServer and UnixWare make excellent use of more than one processor.

Are you worried about support for all your present devices? If you have been using SCO operating systems for a while, you likely have old cartridge tape drives, multiport serial cards, and other peripherals that you wish to migrate to the upgraded operating system. Fortunately, most peripherals that work with earlier SCO UNIX versions will work with both OpenServer 5 and UnixWare 7. Some older multiport cards will require new drivers, usually available from the manufacturer’s Web site or FTP library. Older SCO UNIX drivers will not always wiork properly with OpenServer 5 and UnixWare 7 because of the change in operating system internals, so check the list of supported hardware carefully. Some manufacturers have ceased supporting older cards that ran under SCO UNIX, but many offer reasonable upgrade paths to their latest models.

Installation choices

Installation processes for both OpenServer 5 and UnixWare 7 include fresh (overwriting anything on the disk partitions) and upgrade (trying to retain previous configuration files and filesystems). If you are trying to retain all your old SCO UNIX settings, then the fresh installation won’t work for you as it reformats the filesystems. However, you can make a fresh installation work if you are installing new hard drives as your boot drive. Install OpenServer 5 and UnixWare 7 as a fresh installation on the new drive, then mount your older drive and either copy over or link the files and applications you need. This approach is not an operating system upgrade, but does allow existing filesystems with legacy files and applications to be preserved in their entirety.

Fresh installations do not mean that all data is lost. If you have non-root filesystems mounted on your operating system, they can be preserved and remounted during the installation. However, the root filesystem has to be overwritten when a Fresh installation is selected.

If you are upgrading your primary drive from an older SCO operating system to OpenServer 5 or UnixWare 7, you will want to choose the upgrade option. Upgrades don’t work with all earlier SCO releases, so check the version number you have. If an upgrade cannot be performed the installation will warn you before it makes any changes to the hard drive.

The latest versions of OpenServer can perform an upgrade from any earlier OpenServer release quickly and easily. The upgrade routine removes all the older versions that are in the new release, then installs the latest versions. No user files are affected and the entire upgrade can be performed in about ten minutes. Some user-created files or directories in non-user directories may be renamed automatically because of the upgrade creating new symbolic links.

If you are running Open Desktop Release 2.0 or 3.0 you can upgrade to OpenServer 5 only through the Fresh installation’s Preserve option. Your old root filesystem is overwritten. The same applies to older SCO UNIX and SCO XENIX installations. The changes introduced with OpenServer make it impossible to upgrade those older operating systems without overwriting root filesystems. Non-root filesystems can be preserved.

SCO Merge is not upgraded automatically with any of the upgrade options. It has to be manually upgraded from the OpenServer 5 CD-ROM using custom or the Software Manager.

SCO UnixWare 7 requires a fresh installation from any operating system other than UnixWare 2.1, pretty much regardless of the original operating system release. This is because of the intrinsic differences between UnixWare and the OpenServer lineup. Upgrades from UnixWare 2.1 are smooth. Any non-root filesystem from either SCO UNIX, OpenServer, Open Desktop, or UnixWare operating systems can be preserved across the upgrade, but the root filesystem is reformatted (except from UnixWare 2.1).

Of course, not everything is smooth in upgrade land. There are a few problems that crop up, especially if you have devices requiring special drivers. A few good examples help illustrate this point. Some SCSI controllers (notably Buslogic) require BTLM (boot time loadable modules) in order to function properly. If these are not properly handled during the upgrade process you can lose access to your SCSI devices and the ability to boot the operating system).

Some magneto-optical drives, CD-ROM jukeboxes, and tape libraries require special handling, too, and loading older UNIX drivers can reveal incompatibilities between the operating system versions. Multiport cards present many of the worse problems, as older drivers don’t work with OpenServer or UnixWare. New releases of the drivers must be obtained to enable these devices, often at the cost of having to reconfigure them from scratch.

Application problems can crop up if you are switching from the UNIX-OpenServer side of SCO’s product line to UnixWare. A few applications simply refuse to work with UnixWare 7 even though they run fine under OpenServer 5. There are very few of these cases, but you may need to consider your application migration paths as well as operating system upgrades. This problem is exacerbated if you have applications developed using OpenServer or Open Desktop APIs. There are many calls that behave completely differently or are not supported in the UnixWare 7 and porting across these platforms is a major task.

Wrapping Up

Should you upgrade? If you are not running OpenServer or UnixWare’s latest major revision (OS 5 or UW 7), then most certainly. Your hardware will be better leveraged, your applications will run faster, and you have many more options for supporting new devices. The installation process, while it requires some time, tends to proceed without problems. You will find all your old applications and hardware working better together, thanks to the better kernel design of the new operating system releases.

Still reluctant to upgrade? Think of the support issue alone. SCO doesn’t support older operating systems the same as the latest versions, and if you need help, well, you may be out of luck. There’s no good reason not to upgrade except for reticence. Get up to date. Your users will thank you for it.

Sidebar: OpenServer 5.0.5 and UnixWare 7 upgrades:

The following releases can be upgraded to OpenServer 5.0.5 with no loss of root filesystem data:

Any release of OpenServer 5

The following releases cannot be upgraded to OpenServer 5.0.5 without loss of root filesystem data. A fresh installation is required (however the Preserve option is available for non-root filesystems):

SCO Internet FastStart 1.0 or 1.1

SCO OpenDesktop 2.0 or 3.0


SCO Xenix

The following releases can be upgraded to UnixWare 7 with no loss of root filesystem data:

UnixWare 2.1

All non-UnixWare operating systems require a fresh installation of the root filesystem. Non-root filesystems can be preserved.

Sidebar: Different versions of UnixWare 7 and OpenServer 5.0.5

There are several editions of each current operating system available. UnixWare 7 is available in at least eight different editions, all with slightly different features and requirements. The Base edition contains, as you would expect, all the basic components. The Business Edition adds a bunch of utilities such as ARCserve/Open, the Common Desktop Environment (CDE) desktop, and Netscape FastTrack Server. A set of additional smaller utilities round out the Business Edition. The Departmental Edition and Enterprise Edition are much the same as the Business Edition, the difference is in the number of licensed users. The Development Edition contains tools for software development. The Free Edition is the give-away stripped version of UnixWare 7 which contains almost all the components of the larger systems, but licensed for a single user only. Finally the Intranet and Messaging Editions are tailored for more specific tasks on a network.

OpenServer has three editions: Host, Desktop, and Enterprise. The Desktop edition is a single-user, while the Enterprise edition is for any number of users. The number of users is controlled by adding licenses with no change to the underlying system except an optimization of the kernel.

Installation Tips

Make backups – at least two of them, preferably more, on at least two types of media if possible

Print out copies of important system files (/etc/passwd, /etc/hosts, /etc/ttytype, for example)

Print a copy of the current hardware configuration with IRQ, DMA, and I/O addresses marked (print the output of the command hwconfig –h and then print the last few entries in the file /usr/adm/messages)

Make a manual list of all hardware installed on your system, their configuration, current driver versions, and any custom settings (especially important for multiport cards)

Make a list of all your software, where it’s installed, and any configuration paramters (such as customized printer drivers, license files, and user lists)

Assemble all your diskettes, CD-ROMs, and tapes with drivers, upgrades, and applications before you start. This saves time spent hunting later, delaying the restart of your server.

Save all your user’s mailbox files and home directory contents on a dedicated backup medium

Print and save your mail system settings (especially UUCP or MMDF configuration files)

Be sure of your network settings (adapter and IP address and netmask)

Take your time and install only one component at a time, testing each as you install it

Comparison of UW7 and OS5

Which operating system is better for your upgrade choice, OpenServer 5 or UnixWare 7? That’s almost impossible to answer. However, not all early SCO applications and some SCO UNIX hardware drivers will not work properly with UnixWare 7. Check your application and hardware lists before upgrading to ensure you don’t make a big mistake!

Given a choice between the two operating systems, you’ll find each has its strengths. The table below lists common server applications and the operating system we feel is best for that purpose:

5 7
/ Motif server
access server
/ NIS / YP master
applet server