Microsoft offers Offline System Update Diagnostic Tool for Xbox One
For those of you still unable to connect to Xbox LIVE to download the mandatory day-one update for Xbox One, Microsoft is now offering an official offline option.
Over the weekend, Microsoft posted the Offline System Update Diagnostic Tool, which the company warns "should only be used to troubleshoot a console that’s having trouble downloading the system update from Xbox Live."
"Please exhaust all other troubleshooting before attempting this process, as the diagnostic tool file is a very large file and this troubleshooting process will take considerable time to complete," Microsoft warns.
Before resorting to the offline diagnostic tool, let me suggest first checking out Microsoft's recommended page for troubleshooting your system. If you've exhausted those options, then get a USB flash drive with 2GB of space that's formatted as NTFS and follow the directions posted here.