Juliet Kemp

I am of course sure that everyone reading this is well aware of scripting best practices and always writes beautifully neat and well-set-out scripts that will still have meaning when you return to them in six months time. You might not then need perltidy for your own scripts. Even so, from time to time you […]

Condor is a batch job queueing system, which runs across multiple machines. It takes jobs from users, queues them up, decides where and when to run them, and then returns the results to the user once done. It enables you to turn any group of machines into a cluster-like system — setting up a distributed-processing […]

IPTraf is a very useful ncurses-based application that shows the traffic passing through your machine. On startup, you can immediately see all network traffic on your machine by choosing “IP traffic monitor.” The configuration menu enables you to change the logging interval (under Timers) or add monitoring of ports above 1023, as these aren’t monitored […]

Last week I talked about testing the strength of users’ passwords. Another way to ensure security is to set a good password policy. The PAM module pam_cracklib can enforce both length and complexity. For length, it uses the minlen option. For complexity, it has options dcredit, ucredit, lcredit, and ocredit, which refer to digit, upper-case […]

Enforcing password security with a multiple-user system can be a hassle — users all too often use inadequate passwords. john-the-ripper (also available via most distros) is a password-cracking tool that enables the identification of vulnerable passwords before someone with nefarious intentions finds the weakness. The first step is to extract the username/password information from the […]

Scripting languages are incredibly useful for quick-fix scripts. The problem with this is when the quick-fix script is still in place 6 months down the line, at which point the corners you cut because, hey, it’s just a short-term fix, come back to bite you. Read on for some best practice tips to make the […]

Aliases are great for saving typing time, and you probably already have a handful set up. But you may not be aware that it’s possible to set up aliases that take command line variables as an argument. Read on for an example. Note: You can set up the commands given below either directly from the […]

xargs is an incredibly useful command: it takes in input and executes your chosen command on it: xargs command. Deceptively simple in concept; extremely powerful in execution. It’s most commonly used to execute one command on the output from another command (command1 | xargs command2), and most often the output-generating command is find (xargs is […]

Snapshot filesystems, which offer instant-availability backups from multiple time points, are a great idea. But migrating to a new filesystem is a major deal. rsnapshot works on an ext3 filesystem, using rsync and hard links to create something that looks and works like multiple instant-availability full backups (as with a snapshot system), but that takes […]

The excellent open-source monitoring software Nagios is set up to use plugins to do the actual work of checking services. Here are some useful plugins from the official plugin site and an unofficial plugin collection. check_apt: Checks for apt software updates. The main advantage over cron-apt is that you can centralize your package monitoring: easier […]