Help. Mac big sur update failed, only option to restart in target disk mode

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Help. Mac big sur update failed, only option to restart in target disk mode

Can someone please help me. I tried to install and update Mac big sur on my MacBook Air, however with the last 5 minutes of updating it said there was an error with the system update. I am now left with a black screen, asking me to select the system I want to use to start up my computer. The reset button is greyed out, and the only option available is to restart the computer in target disk mode.

I don’t have another Mac, and I don’t want to use it as a hard disk. I’m quite worried I will lose my data on my Mac, as I don’t have a time machine backup.

I’m not the best with technology, but I saw in another post that some people forced shut down and restarted and this worked? I’m just a bit scared incase I do lose everything from this.

I’m not sure if the update failed due to lack of ‘disk space’. When I clicked about this Mac, the storage space said 39GB. However I have read on another post that ‘disk space’ is not the same as storage space (I wish I knew this before).

Any help would be hugely appreciated, I really want to avoid wiping the Mac and losing everything ☹️

MacBook Air

Posted on Aug 6, 2022 7:15 AM

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Answer 1

Top-ranking reply

Matti Haveri

Level 6

16,571 points

Aug 6, 2022 9:14 AM in response to C-Ange-

If you really do not have a backup, AND do not want to lose data, I'd try target disk mode and copy user data with another Mac to a safe place before doing anything else.

Then try Internet recovery mode to install Big Sur on top of the old system (it should not touch the user data). But if the disk indeed is full, you might have to delete some large user files before the update succeeds (maybe via target disk mode or via the Terminal).

How to reinstall macOS - Apple Support

How to create a bootable installer for macOS - Apple Support

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Answer 2

Tesserax

Level 10

152,019 points

Aug 6, 2022 9:19 AM in response to C-Ange-

Unfortunately, now is not the time to not have a backup ... especially, if the data is critical to you. Sorry, but that is reality and why performing backups are essential.

Depending on where in the update process it failed (you mention within the last 5 minutes), will determine the success of recovery.

Regardless, you now have a number of options going forward.

I would suggest that you do power-down your notebook. This should not cause any further data loss. Then try booting up in Safe Mode. See if the update process resumes. If it does, then let it continue. If it does, not and you are greeted with a "black screen" again, then power-down your notebook again.

Ref: How to use safe mode on your Mac - Apple Support

... and if the latter is the case, I suggest that you make a Genius Bar appointment at your local Apple Store or Apple Authorized Service Provider to have them take a look and provide you with your options. Alternately, you can contact Apple Support directly by selecting the "Get Support" link in the upper right-hand side of this forum's web page.

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Help. Mac big sur update failed, only option to restart in target disk mode

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