How To: Rebuild Linux RAID (Simples!)

Reading Time: 5 minutes

There are many tutorials on rebuilding Linux Software RAID but most are unnecessarily overly complicated. It’s fairly straight forward – here’s how.

Raid1

Unlike hardware RAID, software RAID is all handled by the operating system itself. This means the process of replication, rebuilding and control is performed by the filesystem with various kernel and userspace software.

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How To: Install Tarsnap on Linux

Reading Time: 7 minutes

After posting how great Tarsnap is I thought it only fair to write a ‘how to install Tarnsap on Linux’ article, so here goes.

Sign up for an account

This is the easiest part, simply create an account at Tarsnap.com and verify your e-mail address. You will need to ‘top up’ your account with at least 5 American Pasos to actually get started so may as well do that right away. I used Paypal as it makes me feel safe and when I feel safe I sleep better at night.

Once you have an account balance there’s actually not much else to do via the website; the rest is all command line goodness.

Download and Compile the Source Code

I’m going to do the rest as the ‘root’ user. If you’re not feeling as brave you may wish to prefix every command with ‘sudo’ as your normal user – for some reason Ubuntu et al seem to love doing this.

At the time of writing version 1.0.36.1 was the latest.

First up lets get root and change to /tmp and then download the tarball:

sudo -i
cd /tmp/
wget https://www.tarsnap.com/download/tarsnap-autoconf-1.0.36.1.tgz

tarsnap1

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Tarsnap – The Ultimate Backup Solution

Reading Time: 2 minutes

Tarsnap is a no nonsense backup service for Unix (Linux, Mac etc) and is very nice indeed from a sysadmin’s point of view. It is inherently uber secure by design. It somewhat lacks being end-user friendly though – for example it doesn’t handle expiry of archives out-the-box. Therefore if you wanted GFS style rotation you need to wrap it in something which handles deleting old archives according to whatever deltas.

tarsnap

Their payment model is a bit strange in that it is prepay so you get a warning email when running low on credit or risk having your backups deleted for good. The cost of a particular backup run can Read More »

Energy Monitor Cacti Graphing

Reading Time: 3 minutes

Using an off the shelf energy monitor you can graph your energy using Cacti. The monitor unit I’ve used here is a Current Cost ENVI. E-On were giving these away for free but they’ve probably stopped that now.

CurrentCostENVI

It comprises of a sender unit, with a single phase clamp sensor and an Read More »

Bluetooth Proximity Sensor

Reading Time: 2 minutes

bluetooth-logo

I wanted a way to detect if someone was in the house without anyone having to do anything. This is useful, for example, to run a script or launch a program if we can identify who it is. The solution I wanted to play with was using mobile phones. Given that folks are fairly attached to their phones these days this seemed a reasonable detection method.

The script below is written in Python and uses bluetooth to detect if anyone Read More »