About A.P. Lawrence

A.P. Lawrence provides SCO Unix and Linux consulting services http://www.pcunix.com
Monitoring File or Directory Changes

Many modern systems provide a way to watch a directory for events (new files, reading the directory, modification of a file in the directory, etc.). This facility can be done in various ways, from providing hooks in the filesystem code itself to something that watches for inode changes. Linux and BSD have several possibilities in that regard, including dnotify, changedfiles, and watch.

My Wife Hates my Mac

First: I LOVE my Mac. It’s my wife that hates it. I say that in the hopes of heading off a flood of defensive email. Don’t bother to write me telling me how wrong this article is: you would be preaching to the converted. I already know that she’s wrong, that’s she is just hopelessly corrupted by the Microsoft way. I also know that I’m guilty of not training her in the basics of using this iBook, so yes, it’s partly my fault. Or all my fault if you like.

In Defense of Unix (and Linux, of course)

Warning: This article contains strong language and unpopular opinions. Reading of this material by Windows advocates may cause severe gastric distress followed by a desire to strike the author sharply about the head. As the author does not enjoy being pummeled, such persons are kindly requested to return whence they came and do something else.

Microsoft’s Services For Unix

Gosh, you’d never expect me to say something pleasant about a Windows machine, would you? Well, actually that’s not entirely true: I’ve been known to grudgingly admit that while it isn’t Unix, Windows XP Professional really isn’t awful. In fact, if you can live without Unixy stuff at your beck and call, Windows XP is pretty good – there are even things I actually LIKE about it.

Installing a Small Office Network

For many of us in the SCO world, office networks are a fairly new phenomenon. Many SCO systems are still happily using serial connectivity exclusively, even when Windows machines are part of the enterprise, and even when those machines maybe be networked between each other. In fact, some people even refer to serially connected terminals as a “network” (I won’t use that here: if I say network, I mean an Ethernet network).

VPN’s and Other Remote Access

A VPN is a Virtual Private Network. The concept is that you are using public or other shared lines (generally the Internet) to connect machines, but that all packets are encrypted (so your connections are “private”).

NT vs. Unix

I think it was some Sun piece that said something like: “If all you ever had to do with an OS is install it, NT would be a great operating system”.

Unix Permissions

These are classic Unix permissions. However, many modern Unixes support extended attributes that go beyond this. We’ll look at one example of that later in the article. You also need to know that Unix and Windows permissions don’t map well to each other, so if you are using something like Samba or Visionfs , you need to understand how permissions will be shown and honored. Some examples of that are shown later.

Virtual PC for Mac OS X

Virtual PC for Windows, Mac (OS 9 or X) and OS/2 creates virtual machines that can run multiple Windows versions. This is particularly advantageous for Mac users, but even ordinary PC users can find value in this. It’s easy to have Linux, Windows 98, Windows ME, 2000, XP Home and XP professional all on the same machine.

Kernel Link Failures

That’s a pretty awful feeling, isn’t it? You’ve got to link a new kernel because you need to change a value or needed to add something, and it fails.

Using the shell (Terminal) in Mac OS X

Many Mac OS X users won’t have any need to use the Unix shell that underlies their graphical interface. Some will likely disdain the very idea, but for those adventurous enough to try it, a whole new world awaits.

Operating System Concepts

The CPU (Central Processing Unit) is the heart of any computer, but the operating system is the brain. Unfortunately, understanding exactly how these things really work can be difficult, because it’s fairly hard to “play” with the operating system that you are actually using. You can do quite a bit with sophisticated debuggers, but eventually you run into confusion and difficulty.

Granite Digital SMARTVue for Mac OS X

Self-Monitoring, Analysis and Reporting Technology (S.M.A.R.T) is built into most newer hard drives. S.M.A.R.T records a number of “attributes” that can be reported. These are things like Seek Error Rate, Spin Up Time and more which could help warn of impending difficulties. This predictive and warning function is part of the value for products like Granite Digital’s SMARTVue.

Setting up Netcat Printers

Boy, I like netcat. Just finished converting one client’s SCO 5.0.5 system from Berkeley LPD to netcat and recommend the change to anyone now using LPD to print to dedicated print servers.

How can I print to a remote PC that does not have a static IP address?

This is a fairly common problem: you have a PC at home and you make some sort of connection over the internet to your server, but your application needs to print to your PC. That would be easier if your PC had a fixed, constant IP address, but your connection is dynamic so it changes.

There are many, many ways to solve this problem. So many, in fact. that I’ll probably miss one or two in this write up. If I do miss something, do let me know: it may help someone else down the line.

Network Neighborhood, Visionfs, Samba Authentication and all that

Unix and Linux machines have been able to provide Network Neighborhood style file and print services for some time now, but I constantly see confusion and problems due to misunderstanding of how these things work.

I’m going to use an example from a real situation involving an XP user and a SCO Visionfs network. The concepts of this apply to Linux, Mac, Samba: it doesn’t really matter.

Triple Threat

Good things come in small packages, but large things aren’t always bad either. That must have been the thought someone had in designing an email newsletter for their customers. Apparently they had quite a bit of news; this particular piece of email was 34 megabytes when it arrived at the Mitel SME (E-Smith) server of one of my customers.

Device::SerialPort on Redhat 8

The end of life for Redhat 6.2 security updates happened at the end of March. Because of this, I have been upgrading our remote buildings with Redhat 8. Since each building has a T1 router, I wrote a small program to log the routers messages to a text file.

DSL and Cable Modem Security

Although high speed internet access may not have reached you yet, it probably will soon. The advantages are obvious, but there’s a dark side: security. I’m not going to talk about the more general aspects of securing your system here (I’ve done that in General Security), but only specifically about the issue of clear text passwords with telnet, pop, and ftp.

SCO OSR5.0.6

Because of an unexpected schedule change, I found myself with a whole day open one recent Tuesday.

Counterpoint on Red Hat Linux

Counterpoint (http://www.synchronics.com) is a provider of point of sale and accounting software.


Peek, by Computronics (http://www.computron.com/), is a user monitoring/control tool for character based applications. Most Unix platforms are supported, including Linux and SCO OSR5.


The “setdate” is just a more user-friendly front end to changing the date and time:

Hylafax for OSR5

You’ll probably save yourself a lot of trouble if you just decide now that a better place to run Hylafax is on a Linux machine.