STICKY: Useful Unix commands

For a long time I’ve maintained a memory aid in the form of a list of useful commands which can be used on the command line for Linux, OS X, BSD, Solaris, etc., so I thought I’d list them in a blog post in case they come in useful for others. Most of these will run on any Unix-type operating system, though I’ve usually indicated where a command is OS-specific. read more

Script to detect MAC addresses of new devices connecting to local network

I wanted to get notified of any new machines connecting to my local network so that I could be reasonably sure there would be no unauthorised devices connecting wirelessly to use my network for unknown and potentially malicious purposes. I therefore wrote a simple script to detect new MAC addresses appearing on the network and notify me accordingly. The script requires nmap to be installed and should ideally be run from cron with the output going to a valid email account. The script can be obtained from my GitHub.

Reclaiming storage space on two-node MongoDB replica sets

At they seem to assume we can create MongoDB replica sets using unlimited numbers of instances which have infinite amounts of storage. In practice, however, we often need to use replica sets with only two nodes (plus arbiter) which have limited storage. The problem then is that MongoDB has the tendency to use vast amounts of disk space without reclaiming the space from dropped data, so it consumes ever-increasing amounts of storage. It’s then hard to deal with this storage problem given the limited options available in a two-node replica set. read more

Comparison of keyboards for iPad mini with Retina display

At any given time I’m effectively on 24/7 support for a number of clients, but I don’t always want to carry my laptop with me wherever I go. I therefore decided it would be a good idea to buy a keyboard for my iPad mini with Retina display in order to have a light, very portable hardware solution suitable for most support situations without having to carry my much bigger, heavier laptop around. read more