Erlang B is a commonly used algorithm used to estimate required capacity for a given load. Originating in telephony for estimating required trunks/channels for an expected load, this same algorithm can be applied to any problem where you have a known arrival rate and required Grade of Service - e.g. servers required for given web traffic, lanes required for given car traffic, staff required for given customers in a retail shop, etc. I’m by no means an expert on the algorithm (it involves poisson distributions and clever things mathematicians get exited about). I do however use it so need it available in a format that doesn’t require a maths degree or regularly going to websites, hence Excel. Note also that this does not account for queuing (Erlang C for that) so may not be suitable where you expect and accept a queue, e.g. customers in your store can wait a few minutes and would not typically mind.
Yeah, I’m a geek - I’m running my own Minecraft server. In case it isn’t obvious you can see a realtime map of the world as we escape reality in the link in the menu up top. It’s now open for “public” but I would still class as beta as I’m tinkering quite a bit.
Anyways, feel free to drop in.
Minecraft server address: minecraft.poweredbyjeff.com
I had a need recently to sniff traffic going to an iPhone at home. Nothing nefarious; just trying to figure out why iCloud backup was not working. Anyhow, a decent (and secure) wifi router would typically only send data to the destination hardware address, meaning I could not see the iPhone’s traffic using tcpdump or Wireshark. In effect what I wanted to do is set up a SPAN port in the Tomoto wifi world. Here’s how I did it…
The ‘teamspeak-server’ package built for Debian/Ubuntu at the time of writing this article is only for Teamspeak version 2, but everyone who is anyone these days uses TS3. After trolling around the Internet looking for a prebuilt package I could trust, I decided to roll my own install script. For the impatient here are the steps to get a Teamspeak 3 server installed on Debian-based Linux quickly:
Try this in a test environment first! It requires root privileges and can take your children. You have been warned.
Download and transfer installts3.sh to your server.
Download and transfer the correct server binary to your server.
chmod u+x installts3.sh
sudo ./installts3.sh serverbinary.tar.gz
Replace serverbinary.tar.gz with the name of the file you downloaded from the Teamspeak website. If there are no errors the script will tell you where to get your ServerAdmin privilege key and you are good to go!
Often I would like to access files over SFTP but without the limitations of an FTP client. For example, it’s handy to alter remote files directly in terminal as if they are local, or open them with my nice, fully fledged editor. Mucking around downloading/uploading files each time I modify them gets annoying quickly, especially with something fiddly like web development.
Fortunately SSHFS is now in MacPorts, and provides a quick solution for those on a Mac with SSH access. I could of course configure a file server but that is not always possible, particularly if you don’t have the ablity to install software on the remote machine!
January 2015 update: these days I generally use the powerful SourceTree tool from Atlassian. While it’s great to be a purist, sometimes I just need to get the “job done”. The below still applies when I’m working exclusively in a shell (generally on a remote box).
Spam is really annoying, particularly for anybody maintaining a website with anonymous contribution - in my case via comments. Mollum filters the bulk of the spammers out. Unfortunately if you want to capture anonymous commenter’s contact information in Drupal 7 this also exposes and displays the homepage field. This is also displayed to all visitors to your website that can access this content - incentive for link spammers :(
Had an interesting issue when installing Drupal 7 the other day. I could not find the “teaser length” feature that was present in Drupal 6. This appears to be expected behaviour, however I could not see the “Manage Display” and “Manage Fields” options in the Content Types settings.
If you selected the “minimal” profile during install, the “Field UI” module will not be enabled. Turn this on and the “Manage Display” along with “Manage Fields” become visible and you can follow your nose from there.
Couldn’t help it, had to put something here. I pulled down the site some months ago (perhaps as many as 12). I think the goal at the time was to upgrade to Drupal 7, but as often happens life got in the way.