The major outage that hit tens of thousands of websites using Amazon's AWS cloud computing service on Tuesday ends up having been the result of a simple typo — just one incorrectly-entered command.

On Tuesday morning, an Amazon team was investigating a problem that was slowing down [a] billing system.

At 9:37 am Pacific time, one of the team members executed a command that was meant to take a few of the [billing] servers offline.

"Unfortunately," Amazon said in its posting, one part of that command was entered incorrectly — i.e. it had a typo.

That mistake caused a larger number of servers to be taken offline than they'd wanted. Two of those servers ran some important systems for the whole East Coast region, such as the ones [responsible for] trillions of files [on] customers' websites.

To get it back, both systems required a full restart...It wasn't until...four hours and 17 minutes after the mistyped command was first entered that the entire system was back up and running.