Power outage during Big Sur 11.5.2 Update. Is my iMac OK?

Question

Level 1

144 points

Power outage during Big Sur 11.5.2 Update. Is my iMac OK?

A couple of nights ago, mu iMac was updating to Big Sur 11.5.2 when we had a power outage. I ran over to my beeping UPS and saw I still had some longish amount of time to complete the update. I don't remember how long but knew my UPS wouldn't last that long, so I forced the iMac's power off with the button in back.

The next morning I booted up and everything *seemed* normal with the OS listed as 11.5.2. I ran Disk Utility on the Fusion drive container and both volumes; everything checked out. I ran EtreCheck, and it found nothing unusual.

Only once at the end of the day did I find anything wrong — Safari wouldn't quit on shutdown. (I've since cleaned its cache and it quits normally now.)

I'm really skeptical that everything really is okay — otherwise, why would the update have needed so much more time to complete?

Can anyone suggest a way I can really verify the integrity of my system (and yes, System Integrity Protection is enabled)? I really don't want to have to reinstall Big Sur from scratch.

iMac Line (2012 and Later)

Posted on Aug 20, 2021 4:16 PM

Reply

Answer 1

Top-ranking reply

Psychovirus

Level 1

110 points

Aug 21, 2021 3:22 AM in response to Robby Berman

Hey there!

It's strange that you were not asked to install the macOS again even though it didn't finish successfully as you mentioned. Though it's hard to verify if the macOS is corrupted, I would suggest to observe your device in safe mode if you're experiencing any issue. It could be possible that everything is alright and you're just sceptical about it. If so is the case, you can wait and observe.

If you want to sleep peacefully without worrying about a corrupted macOS, reinstall macOS through recovery would be a wise choice.

https://support.apple.com/en-us/HT204904

Reply

Answer 2

PRP_53

Level 10

91,243 points

Aug 21, 2021 3:47 AM in response to Robby Berman

Good advise from previous posting regarding Reinstall from Recovery Mode. Just be certain to perform a Time Machine Backup before performing this actions - insurance incase things go sideways.

The Reinstall from Recovery will load the full installer and only over-write missing or corrupted elements of the System Files without touching Applications, Settings, Personal files etc.

Reply

Answer 3

Robby Berman Author

Level 1

144 points

Aug 21, 2021 2:32 PM in response to PRP_53

It took about an hour, but was uneventful, and now I can stop giving my iMac the sideye. I was highly suspicious after everything seemed okay with so much update time left at the time of the power outage. Great feature, too, being able ro update and check the OS install in place without wiping the hard drive.

Reply

Answer 4

Robby Berman Author

Level 1

144 points

Aug 21, 2021 9:36 AM in response to PRP_53

Ah, this makes sense. I'd assumed reinstalling the system would require erasing the drive and that whole reinstallation nightmare. I'll definitely do this for peace of mind. Thanks to you both.

Reply