Picture Frames and Captions with ImageMagick

This article discusses some of the caption and border effects available with the ImageMagick image processing package. ImageMagick is freely available for Linux and Windows. It offers a huge number of image processing options, so many in fact, that using the program can be a little tricky.

The following examples were evolved from the ImageMagick online documentation, plus a good deal of trial and error to get the details right. I used Linux, but the same commands should work under Windows. Continue reading

Simple Picture Gallery on Raspberry Pi

The Raspberry Pi is a small Linux computer designed to help children learn programming. Being a full Linux System, it can also be used as a server or as the basis for various projects. The Pi’s low power consumption makes it particularly suited to the role of always-on web server.

This post describes how to create a simple photo gallery on the Pi, which can be shared over the internet with or without password protection. While not as polished as Flickr, Smugmug or similar services, it allows you to retain ownetship, control and security of the shared images. Continue reading

Solaris Tictimed Catastrophic File Error

Solaris administrators may have seen the message “Catastrophic file error – zero length” in their system logs. Although it sounds serious, there is nothing “catastrophic” about it. This post explains how to stop the message from flooding your log files. Continue reading

Network Scanners and Fedora 20

Here is a quick fix that might help users experiencing the “no devices available” problem when using xsane, the Linux scanning tool.

In this case, the device was an HP 3070 B611, a combined printer and scanner. The OS (Fedora 20) was able to see the device as a printer and print okay, but the scanner part did not work. Xsane just popped a small window saying unable to find device.

The fix was a change in the CUPS configuration, and it may therefore work with other versions of Linux.

Note: (19th June 2016) This article receives an unexpectedly large number of hits.  If you have come here expecting something else, for example information about network scanners like nmap or Wireshark, please leave a comment to that affect and I will adjust the keyword settings.  This article is about document scanners, not software to snoop your LAN.

Continue reading

Reuse a spare BT Home Hub as a Wireless Access Point

This article was rewritten and updated on 9th April 2017.

BT is a popular Internet service provider in the UK.  BT subscribers receive a free router called the “BT Home Hub“.  A new model of Home Hub is launched every few years, and as BT never takes the old ones back, many people have an old Hub tucked away somewhere, gathering dust.

This post explains how to convert an old BT Home Hub 5.0 or Home Hub 4.0 into a second wireless access point (“AP”) on your network, strengthening and extending the wireless signal around your home or office.  Although the details are for those routers, the basic procedure works for other BT and perhaps non-BT routers.  In particular, notes have been included for the BT Home Hub 3.0 and the now ancient Home Hub 1.0 – these are indented and written in italics.  Many users have also had success in reusing Home Hub models 2.0 and 6.0 (BT’s latest router, also known as the Smart Hub). Continue reading

An Example of Parallel Processing

This post shows how to use parallel processing to get a CPU intensive job done faster in Unix/Linux. By splitting a large task into several parts, it is quite easy to give each part to a separate CPU, and complete the task many times faster than it would on a single processor.

These days, even small PCs and other devices often come equipped with several CPU cores. But some tasks will use only one core, sometimes using 100% of it, while other cores stand by idle. Sometimes this is a waste of resources. Continue reading

Simple Webcam on Raspberry Pi

The Raspberry Pi’s low power consumption makes it well suited to the role of always-on server. This post describes how to attach a simple webcam to a Raspberry Pi and have it take a snapshot every few minutes, and how to view the pictures on the web. Just like a traditional webcam.

My Raspberry Pi was purchased from New It in the UK. It was installed with Debian 7 (“Wheezy”) by applying the image “2014-01-07-wheezy-raspbian.zip” downloaded from the raspberrypi.org downloads page. The following procedure was then performed without any further pre-work (other than enabling ssh in the basic setup). Continue reading

bc Rounding Errors

There must be a few people out there who still use bc as a desk calculator. bc is a simple application that comes as standard on most unix and linux systems. It’s nicer to use than a graphical calculator app: less fussy, no mouse needed and you can see what you have typed.

bc Gets it Wrong

A recent mix-up with financial calculations lead me to discover that – unbelievably – bc was getting its sums wrong. This post explains the problem. Continue reading

Install WordPress Blog on Raspberry Pi

The Pi’s low power consumption makes it well suited to the role of always-on web server. This post describes how to install WordPress on the Raspberry Pi and get a blog going. Hosting your own blog means you keep ownership of your own data, and you are not dependant on blogger.com or whoever.

If you have already installed WordPress and just want to upgrade it, perhaps because a new version has been released, please see my article How to Upgrade WordPress on Linux

My Raspberry Pi was purchased from New It in the UK and runs Debian 7 (“Wheezy”).

Install Apache

Install the Apache web server with these commands. It might take 10 minutes or so to complete. A few other packages will also be installed. Continue reading

BT Home Hub Cannot Access SSL Website

This article explains why the BT Home Hub routers appears unable to access SSL/TLS (https) websites on your internal home network.  It may interest users in the UK, where the Home Hub is a popular router/ADSL modem.

Hosting your own website(s) at home is pretty easy these days.  You have a small server running Apache, and configure your router to forward port 80 to it.  For SSL sites, you forward port 443.  That’s about it. Continue reading