iphonetetheringwifi
My iPhone 4S, which i got in October, just crashed out of the blue and wouldn't restart.
After reading other people's blogs I managed to restart by holding the main button and on/off button together.
When it rebooted, the wifi and personal hotspots were greyed out and therefore could not connect to the internet. After switching the phone on and off, the wifi reconnected but the Personal Hotspot is still greyed out.
Where has my Personal Hotspot gone and how do I reconnect it?
I was also scratching my head just to share my one iPhone internet to tether via my iMac. It was so silly what solved the problem.
Uncheck the internet sharing checkbox in sharing system preferences.
After unchecking the internet fields were enabled.
Per @SeeMeCode's answer, you can re-install iTunes to solve the problem.
Solved.
I found the solution here. It's caused by a damaged kernel extension /System/Library/Extensions/AppleUSBEthernetHost.kext.
When I check /var/log/system.log, sure enough there is:
Sep 17 08:00:58 wagner.local com.apple.kextd[45]: Kext id com.apple.driver.AppleUSBHostMergeProperties not found; removing personalities from kernel.
Sep 17 08:00:58 wagner.local com.apple.kextd[45]: ERROR: invalid signature for com.apple.macos.driver.AppleUSBEthernetHost, will not load
This extension is installed with iTunes, so the cause was update to iTunes 12.3, not iOS 9. I tried to download iTunes and reinstall it, but it just installed the same damaged version of the kernel extension. So instead, I replaced it from a Time Machine backup as both the currently installed and the backed up version had the same version number 7.0.
After a restart, USB tethering works again.
To distinguish between the two, here's what the working one looks like:
$ ls -lR /System/Library/Extensions/AppleUSBEthernetHost.kext
total 0
drwxr-xr-x 6 root wheel 204 Jan 10 2015 Contents
/System/Library/Extensions/AppleUSBEthernetHost.kext/Contents:
total 16
-rw-r--r-- 1 root wheel 3202 Jan 10 2015 Info.plist
drwxr-xr-x 3 root wheel 102 Jan 10 2015 MacOS
drwxr-xr-x 3 root wheel 102 Jan 10 2015 _CodeSignature
-rw-r--r-- 1 root wheel 474 Jan 10 2015 version.plist
/System/Library/Extensions/AppleUSBEthernetHost.kext/Contents/MacOS:
total 128
-rwxr-xr-x 1 root wheel 63024 Jan 10 2015 AppleUSBEthernetHost
/System/Library/Extensions/AppleUSBEthernetHost.kext/Contents/_CodeSignature:
total 8
-rw-r--r-- 1 root wheel 3668 Jan 10 2015 CodeResources
And the damaged one:
$ ls -lR AppleUSBEthernetHost.kext
total 0
drwxr-xr-x 5 ischeini staff 170 Aug 5 00:30 Contents
Contents:
total 16
-rw-r--r--@ 1 ischeini staff 3202 Aug 5 00:30 Info.plist
drwxr-xr-x 3 ischeini staff 102 Aug 5 00:30 MacOS
-rw-r--r--@ 1 ischeini staff 473 Aug 5 00:30 version.plist
Contents/MacOS:
total 144
-rwxr-xr-x@ 1 ischeini staff 71792 Aug 5 00:30 AppleUSBEthernetHost
Best Answer
Since there wasn't physical trauma, you should try to restore its factory settings through iTunes.
You can try to restore your backup afterwards (iTunes will ask you if you want to or use the phone as a new iPhone), and see if it's still working. That should bring back your Personal Hotspot.
If not, re-restore it and set it up as a new iPhone. You'll lost your messages and some settings. But you should be able to keep your contacts (if sync through iCloud, Gmail, or other), and your mails.
If it's still not working, bring it back to an Apple Store, they'll most likely give you a new one.
Since the Personal Hotspot feature is controlled by your carrier, so you might also want to check with them if it's still activated on your account.