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On January 30, 2007 an oily capacitor bank at Hydro One’s Richview transformer station in Toronto failed, shot a powerful arc of electricity to the ground, and then exploded. The result was a power dip of roughly 1,500 megawatts of capacity, and though it lasted for less than a second, this mysterious blip turned the stuff of nightmares widespread data loss into a frightening reality for business owners from here to the Quebec border and down into the U.S.

In this article I’ll explain how to setup 2 Linux servers to automatically sync data between a specific directory on each server. To do this we will use rsync, ssh key authentication, and a cron job.

Let’s call the 2 servers ‘SOURCESERVER’ and ‘DESTSERVER’ for

SOURCESERVER = Source server (the server we’re connecting from to upload the data)

DESTSERVER = Destination server (the server we’re connecting to receive the data)

Part 1 - Setting up SSH key authentication

First, we need to make sure the DESTSERVER has the ability to use key authentication enabled. Find your sshd configuration file (usually ‘/etc/ssh/sshd_config’) and enable the following options if they are not already set.