Barring unseen developments, tomorrow should see the official release of iOS 9. Macworld put together this short take on getting ready for the upgrade.

The article starts with the expected advice to back up your devices before you start on the upgrade. Sage, if not obvious, advice.

But the thing I found most interesting was this take on making sure you have a way back if things go south:

Here’s the deal: Apple “signs” versions of iOS. This tells the device that the version you wish to use is OK to use with that device. While that version is signed, you can install it on your iOS device—even if it’s a version of the operating system that’s earlier than the one you just installed.

However—and this is very important—Apple traditionally stops signing old versions of iOS just a day or two after releasing major updates (such as iOS 9). If you were to update to iOS 9 say, a week after it ships, you might find that you can’t go back to iOS 8.

Read the post to find out how to locate the old updaters on your hard drive and, failing that, find them online.