iOS 9 beta 1 back up corrupt?

You're not the only one having this issue, so the good news is that your backup probably isn't corrupt. Quite a few people using the same phone are getting the same issue trying to restore from a backup made in Beta 1 after updating to Beta 2.

Yes, reinstalling Beta 1, restoring the backup, and then updating OTA to Beta 2 has been shown to be a workaround - the problem is that you can't download Beta 1 from Apple anymore - you'd have to get the .ipsw from elsewhere and restore your iPhone to it using iTunes.

Even if you can get the the Beta 1 .ipsw, installing it is tricky because you've already got a later version of iOS installed.

You might prefer to use one of many 3rd party iOS Backup manager tools that are available. Some are free and some are paid, but they're effective in situations like these.

Thanks Max.

Having never experienced this issue in the past... Is there any particular third party iOS backuo manager you would recomend?

Assuming you have a Mac:

1. Open iTunes and go to “Preferences”
2. Choose the “Devices” tab to see a list of current iOS Backups on the computer
3. Select the backup you want to make a copy of and right-click it, choosing “Show in Finder”
4. The backup chosen from iTunes will automatically be selected in a new Finder window – note the name will be some alphanumeric jumble like “eef541c486577cbef71123c” and not anything particularly intuitive
5. Duplicate the folder, or just copy the folder to a new location (this is a backup of the backup just in case)
6. Open an iTunes backup manager app (iBackupBot is free and works for this purpose).
7. Navigate to your iPhone's backup (the original one, not the copy).
8. Nivigate into the following folder: HomeDomain/Library/Preferences/
9. Delete com.apple.coreduetd.batterysaver.state.plist
10. Quit the app, return to iTunes and try again to restore to the backup you just modified.

This should work but, if it doesn't, you can still use a backup manager to extract parts of the backup and restore them to your iPhone directly.

I should add that the HomeKit folder doesn't contain any of your user data, it's just the folder that iTunes has been interpreting as corrupt.

Thanks again for your comprehensive answer Max!

I didnt realise you couldnt promote 3rd party apps here (first time using forum today).

Where is the iphone back up stored? I'm using a Mac.

^^^ Added instructions to the step by step guide above ^^^

Any luck with the backup surgery?

I've found the back up, used 2 different (free) third party applications to search it, but I can't find a 'System' folder or 'Homekit'.

What am i doing wrong? Clearly I'm blind 🙂

Cancel that - I've found both a 'HomeKit domain' and also a 'Home Domain' - Should I delete both, or just the HomeKit one?

Just the HomeKit one.

Done, but it only lets me delete the contents of the homekit folder, and not the homekit folder itself.

Restoring as we speak... Fingers crossed it gets to the end with no error.

Well done. Just to check, you were editing the original one right? (iTunes won't be aware of the duplicated backup or any changes made to it)

I edited the step-by-step guide above in case someone else finds this useful. Is it easy to follow?

The (edited) guide is very easy to follow, pretty much an idiots guide! Yes, I did have the same thought and double checked I was editing the original and not the duplicate I'd copied and saved 🙂

Didnt work, same error as before 😟