Those who are planning on purchasing or using the Xbox One will be required to download and install the "Day One" update from Microsoft. However, if you wish to avoid an Xbox Live server slowdown when the entire world downloads the update, you can download the update right now and save it to a USB thumb drive for installation.
Microsoft has put up a guide, which you can access by hitting the VIA link below, that offers you step by step instructions on how to check what Xbox One operating system version you are running, how to save the update to your PC or USB drive, and how to use that USB drive to update your Xbox One.
The update is known as the Emergency Offline Update. "The Emergency Offline Update (EOU) can be used to perform a system update to a console that’s having trouble downloading the system update from Xbox Live," Microsoft explains.
Head over to the VIA link below to check it out.
Update: It appears Microsoft has pulled the update. Looks like this update wasn't supposed to be available yet.