2020 Macbook Air: Carbon Copy Cloner vs the T2 chip

18 Apr 2020 11:53 | macOS

I love Carbon Copy Cloner, it is an awesome piece of software. I frequently rave
about it to anyone who'll listen, it's so useful.

It does however seem to have been somewhat limited by the introduction of
Apple's new T2 security chip. I recently purchased one of the new 2020 Macbook
Airs - a great computer and my first mac with the T2 chip.

My usual process when I get a new mac is to transfer everything over from my old
one using an external SSD and Carbon Copy Cloner. After plugging the drive in to
the new computer I discovered it wouldn't boot from it as the T2 chip has
external device boot disabled by default. Not a major problem, it was simple
enough to enable it.

So I booted into my clone drive, opened CCC and created a restore task. I
clicked go and then the unexpected happened - CCC said it couldn't proceed
because the source drive was FileVault encrypted but the destination wasn't. I
hadn't seen this before, but the recommended workaround was to simply turn off
FileVault on the clone drive. Not ideal but not the end of the world, so I did
that and everything seemed to work.

After an hour or so the sync was finished and I booted the mac normally, and all
my stuff was there. It took around a day or two to sync all my data back down
from iCloud, as is normally the case. When that was finally done I thought
everything was good.. until I tried to set up ApplePay.

"Apple Pay has been disabled because the security settings of this Mac were

Interesting. Also vague, and not super helpful. I rebooted into recovery and
checked the startup security utility - everything looked good, it was set to the
maximum security level and boot from external devices was disabled. Rebooted but
again, same error.

I checked the log stream from the terminal and saw it was failing to initialise
the ApplePay system with an error message that included the phrase "Kext check
failed". Interesting. I had a couple of 3rd party kexts loaded so I removed
them, rebooted, but again got the same error. At this point I started wondering
if this might be an artefact of having restored from a CCC clone, so I hopped
onto a friendly irc channel to ask some mac nerds.

I was immediately told that you should never restore a clone onto a T2 mac.
Instead you have to always use the Migration Assistant or you'll run into issues
with the T2 chip just like I did. I was advised to start again with internet
recovery so I made sure my clone drive was up to date, rebooted, erased the
startup disk, rebooted again and launched internet recovery.

At this point it was late in the evening and I figured this was going to be a
time-consuming pain but not the end of the world. Unfortunately things didn't
quite go to plan. The initial download of the OS from internet recovery seemed
to work, the machine rebooted and said 12mins remaining but then after a moment
or two it suddenly bounced back into the GUI and said:

macOS could not be installed on your computer

An internal error has occurred. : (-69624)

Quit the installer to restart your computer and try again.

This was very disheartening for a brand new machine. Hoping it was some kind of
transient network issue I rebooted and ran through the process again. Same
error. I tried removing my startup security password and ran it again, same

I glanced at my clone drive, remembering it had a recovery partition, and
thought maybe I could reinstall using that. First I'd have to enable booting
from external devices, so I tried to open the startup security utility, only to
find that it refused to do anything because it couldn't authentiate me against
an admin account on the system disk (which was now blank) and I'd removed my
password. It seems that it might be worth setting a startup security password
just to have a fallback authentication method for this scenario.

At this point I did some googling, found a few people who'd run into the same
issue, one of whom ending up returning his machine for a logic board replacement
as a result. At this point I was feeling depressed, a 2-day old machine turned
into a brick because Apple apparently couldn't make a reliable recovery service.

Finally as a last resort I went through a methodical sequence of steps:

1) Powered off
2) Reset the PRAM and NVRAM
3) Booted back into internet recovery and erased the system disk
4) Powered off, reset PRAM and NVRAM again
5) Booted back into internet recovery and restarted the installer

I don't know if any of these steps made a difference or whether there was a
transient issue that resolved itself but thankfully this 3rd time the installer
worked and the machine was back into a usable state.

After installation I plugged my clone drive in and used the Migration Assistant
to restore my data. I was actually impressed at how well this worked - I'd
always assumed a full-system clone with CCC would be a better experience but the
Migration Assistant did really well and completed very quickly.

I did run into a few minor issues with it:

1) After it completed my first login attempt resulted in a perpetual spinner,
but a simple reboot resolved it

2) Some of my system settings were restored to defaults but that's not really a
major problem

Other than those two minor glitches the system is exactly as it would have been
if I'd restored from the clone, except that Apple Pay now works and it also
didn't re-download all my photos from iCloud.

So a bumpy road but ultimately successful.

I have since reached out to CCC support to ask them if they'd consider adding a
warning to the application when attempting to restore a clone to a T2 mac.
Hopefully if they do this it will prevent others from going through the same
trouble. I can easily imagine many people restoring clones, noticing Apple Pay
doesn't work and not connecting the dots - likely leading to many hours on the
phone to Apple Support.

Much thanks to Branes and Cpuroast of ##apple for their help in resolving this!