Situation: SWMBO MacBook Pro has failed to start normally, but will start and operate in safe mode. The MBP will hang up as it starts in normal mode, saying that "the MacOS installation couldn't be completed."

The internet is awash with simple and helpful tips. Complicating the situation is that I was stupid when I turned off her Time Machine backup when I installed the Google WiFi devices and connected her MBP there. So, until yesterday, I didn't have a backup of an important Quicken file. I also reconnected the MBP to the Airport Time Machine and made a backup, but operating in SAFE mode I'm not sure what kind of backup I did make.

I'm very tempted to repartition the hard drive and reinstall the OS, and rebuild applications from scratch. Her iCloud account, images, and all that are backed up, of course. I made a static backup copy of her documents, her photos, her music, etc. to a Thunderbolt SSD, as well as the Time Machine backup. All in safe mode.

The machine has been working fine in safe mode. But, it won't start in normal mode.

What path would you chart?

This message has been edited. Last edited by: 4MUL8R,

Which MBP & OS version?

If it starts openly in safe mode, that means some startup or login item is corrupting the system when & gives you the error when it tries to load.

In the mean time try testing your login items:

1. Choose Apple menu > System Preferences, then click Users & Groups.

2. Click your account name below Current User, then click Login Items at the top of the window.
Make a list of the login items—you’ll need to remember them later.

3. Select all of the login items, then click the Remove button (-)

4. Choose Apple menu > Restart.

5. If this solves the problem, open Users & Groups preferences again, add the login items one at a time, and restart your Mac after adding each one.
When the problem occurs again, follow the steps above to remove only the last login item you added.

Good luck.

quote:

What path would you chart?

If above fails, find a place to stay for the night.LOL

Hopefully, you have a solution.

Can you select a Time Machine backup from
an earlier time that is not corrupted to restore?
Regards, Jack

quote:

Originally posted by 4MUL8R:
What path would you chart?

First see if you can clone the HDD to an external USB HDD, for safekeeping (true clone, not just a backup of data files, using Carbon Copy Cloner or Super Duper).

You can reinstall the OS *without* partitioning or wiping the disk. Either use a USB installer stick if you have one, or the regular install from the Recovery Partition (Command-R during boot). Just choose "Install macOS" (or OS X). This will refresh all of the system files without disturbing your data. You might have to tweak a thing or two, but otherwise it leaves your stuff alone and just reinstalls the system.
 
If that fails to give you a working machine, then wipe the disk and reinstall the OS from scratch. If you were able to clone the HDD (above), then you can migrate your apps, data, and settings during the install, or later with Migration Assistant. You might also be able to migrate from your questionable (unknown) Time Machine backup.
 
Worst case, you weren't able to clone the HDD first, so you have to rebuild the system from scratch.

It sounds like you might have had an OS upgrade interrupted (the "installation couldn't be competed" message). If you have recently tried to do this manually, try doing it again from safe mode (including downloading the update files).

It might help to review the OS upgrade process. It happens in two steps, first the new OS install package is downloaded, then, the next time the system is booted, this package is installed as part of the boot process.

The previous advice about backups, etc. is sound, but this might be a shortcut to a working system.

This happened to me recently on an older MBP. It was trying to install an update and hung up. I followed this advice and it worked fine for me. (You don’t have to download the combo update once you get back in. But if your problem is a hung installation, the first three steps from this site will get you back up again.)

https://jeroenmols.com/blog/2017/12/26/macosupdate/

You didn't specify the MBP's age, but I've seen this before on a machine where the HDD is failing. Is it old enough to have a spinning drive? If that is the culprit, wiping the HDD and doing a new install will fix it for a short while. If it is an older machine, I'd install a new SSD before I go through the process. If you are running High Sierra or newer, Trim is enabled for third party devices automatically, so no need to worry about using third party devices.

quote:

Originally posted by mrbill345:
Which MBP & OS version?

If it starts openly in safe mode, that means some startup or login item is corrupting the system when & gives you the error when it tries to load.

In the mean time try testing your login items:

1. Choose Apple menu > System Preferences, then click Users & Groups.

2. Click your account name below Current User, then click Login Items at the top of the window.
Make a list of the login items—you’ll need to remember them later.

3. Select all of the login items, then click the Remove button (-)

4. Choose Apple menu > Restart.

5. If this solves the problem, open Users & Groups preferences again, add the login items one at a time, and restart your Mac after adding each one.
When the problem occurs again, follow the steps above to remove only the last login item you added.

Good luck.

There were two items in the menu. One named iTunes helper, and the other named Garmin Connect. I deleted both, restarted in normal mode, and it worked. Hope the ship holds together for a few more years.

iTunes Helper is an Apple application.

What does iTunes Helper do?

quote:

Originally posted by mrbill345:
iTunes Helper is an Apple application.

What does iTunes Helper do?

Thanks for the link, that is a great website.