Apple users with jailbroken iPhones, iPods or iPads are unable to update their devices to iOS 8 via ‘Over-The-Air’ (OTA) update, as direct updates from the Apple would be disabled with evasi0n and Pangu jailbreaks.
Those who are trying to force the OTA update on jail-broken devices will invariably encounter the ‘Checking for Update’ loop screen as the idevice will no longer respond to their command.
This is done to ensure that jailbreakers cannot inadvertently install the new updates that could be compromising their existing jailbreak tweaks & apps.
In the other words, it means jailbreakers are left with a sole option of updating their idevice manually only via iTunes, if they are willing to lose their jailbreak tweaks and apps.
Device Compatibility for iOS 8
iOS 8 will be available as a free upgrade to the following i-devices:
iPhone 4s, iPhone 5, iPhone 5c and iPhone 5s
iPad 2, iPad 3, iPad 4 and iPad Air
1st gen iPad mini, Retina iPad mini
5th generation iPod touch
Pre-requisites before Update
Check your device compatibility by verifying if your idevice is listed above.
Download the new version of iTunes for Windows or Mac from here.
Back up your important data on your iPhone, iPod or iPad Touch via iTunes or iCloud:
To Back up via iCloud: Go to Settings > iCloud > Storage and Backup and turn on iCloud Backup button. Once the iCloud Backup is enabled, you will see prompt saying “Back up Now”. Click the Backup button and wait until the process completes as the backup time depends on the content stored on your device.
To Back up via iTunes: Connect the iPad or iPhone to PC or Mac via a USB cable and launch iTunes app. Choose the option “This Computer” under the Backups section of the iTunes. Click the ‘Backup Now’ button and wait until the process completes.