SCO Linux 4

SCO Linux 4 provides the bare bones of a high-availability clustering solution.

Both sendmail 8.12.6 and postfix 1.1.11 are included. Apache 1.3.26 (rather than 2.x) is included with all the usual modules. Apache works right out of the box, serving up a “Hey, it worked!” page with a handful of useful links. Both Sun and IBM Java are present, along with JServe and Tomcat. Samba 2.2.5 and OpenLDAP 2.1.4 are included, along with pam_ldap and other support libraries. The Squid 2.4 caching proxy server also is provided. Tape backup is handled by Amanda 2.4.2, which allows you to use one server with a big tape drive to back up many systems.

SCO Linux 4 also provides the bare bones of a high-availability clustering solution: packages for Linux Virtual Server, DRBD, Heartbeat and Mon. Very little documentation about these services is available, either installed on your system or on the SCO web site. The SCO web site, under its Knowledge Center heading, has one technical article on Heartbeat that is helpful, but there is nothing on LVS, DRBD or Mon. The Red Hat web site contains much more documentation on high availability than this, and SCO Linux 4 has no equivalent of the Red Hat Cluster Manager.

SCO also includes their sysinfo tool. It's a script in /etc that looks all over the system, pulls out a lot of useful information and builds a web page with the results. Anyone supporting a large number of servers will like this feature.


SCO makes support information available on their web site. Most of it requires you to log in before you can access it. Unfortunately, there isn't much information there yet, and what is there is organized in a confusing manner. For instance, a page for Security Advisories ( does not list any security advisories for SCO Linux 4. All information about SCO Linux 4 is in the Support Knowledge Center. At press time, there are 64 technical articles covering SCO Linux 4; 56 are notices of new packages (security patches or upgrades), four are bug information articles and four are general information articles. The general information articles include the Heartbeat article, an article on setting up Squid, how to allow root to log in remotely and where to get System V compatibility libraries.

The UnitedLinux installer can be automated with an XML options file. It also can import configuration files from Red Hat's Kickstart and convert them to the UnitedLinux XML format. There is no documentation about these features, however, either on the SCO web site or on the system. After I inquired about this, SCO technical support sent me a URL to a page on the SuSE web site that documents this information.

SCO's phone support was good. When I called SCO technical support, the people I spoke with were able to answer my questions quickly. They also followed up by e-mail to make sure my problems were solved. SCO has promised to support all releases of SCO Linux for a minimum of two years.

Updates are handled with the Advanced Package Tool (APT) system. APT originally was developed for the Debian GNU/Linux distribution, but Conectiva ported it to work with RPM packages. Once you have registered with SCO, you can update all packages on your system to the latest with one command, or you can update only specific packages. If you update a package that depends on other packages, APT updates the other packages as well, automatically. APT can get the packages from SCO's servers, using the Internet or from a Service Pack CD.

SCO's upgrade policy states you are not required to upgrade any packages if you don't want to do so. If you are calling support with a problem, though, they may tell you to upgrade some packages as the solution to the problem.

A Security Problem

During this review, SCO did not make an important security update available quickly, although other distributions did. On March 3, 2003, the CERT Coordination Center published a remote root compromise in sendmail, reported by Internet Security Systems. Red Hat and SuSE had patches available the same day as the CERT announcement, but SCO released their patch 11 days later. This left the phone support person in the unenviable position of having to tell me that no update was available. He did, however, send an RPM to me for testing. This RPM turned out to be the same one that was ultimately released a week later. It is surprising that SCO would take so long to release a major security patch to sendmail.

In the meantime, I downloaded the SuSE RPM for sendmail and tried it out; it installed with no problems. If the SCO phone support person had not been able to get the RPM to me early, I could have installed the SuSE RPM as a temporary fix.