So if you have a jailbroken device with Pangu or an older jailbreak simply you cannot use device software update.
We will have to update manually through iTunes:
- iOS 8 is supported for the following devices: (iPhone 4s, 5, 5c, 5s/iPad 2, Air, Mini with Retine, Mini)
- Make sure you have the latest iTunes installed.
- Connect your device to the computer via USB and wait for iTunes to launch.
- Back up your device, so if anything went wrong you will be able to restore your data back.
- Click on the device photo, Check for updates
- If the iOS 8 is available it will download it automatically.
- If not then go to IOS 8 Download and download the right version of iOS 8 according to your device model.
- After the firmware file has been downloaded, Hold down on the Option key (Mac) or the Shift key (Windows), and click on “Check for Update”. This will open the file manager. Now select the firmware file and click on the Open button to restore your device.
- iTunes will update your device to iOS 8.
- Enjoy