Solution for macOS installation stuck at "Less than a minute remaining..." (Ventura, Monterey, Big Sur...)

Hi everyone,

I've recently faced the problem related to a macOS installation stuck at "less than a minute remaining" with a 27-in 2017 iMac, and it took me 2 days to finally sort it out. Today I'd like to share some troubleshooting guidelines to help people having the same issue -- as thoroughly reported in:

Big Sur installation stuck at "Less than … - Apple Community

I know there are tons of other articles and YouTube videos about this, but none of them was decisive in bringing me to the solution. Many of them present some nonsensical, potentially harmful steps to take.

First, some context.

Suddenly, after a fresh boot my macOS Ventura started to become very slow and hanging without any apparent reason. It was even impossible to reboot it from the Apple menu. So I manually powered it down. After booting up again, it wouldn't go past the login window for any user: After the password, the loading bar would get stuck at half way, and after about 15 min the system would crash and reboot by itself. After many attempts to log in, I decided to reinstall the system.

Installation attempt: Ventura via Recovery Mode.

I rebooted into local Recovery Mode (Cmd + R during boot) to reinstall macOS. But after a whole night, the installation just wouldn't finish. I then rebooted the machine, but whenever I tried the Recovery Mode, the screen would get stuck at the Apple logo.

I followed:

How to reinstall macOS - Apple Support

Installation attempt: Internet Recovery Mode with Sierra.

As the normal Recovery wouldn't load, I then tried the Internet Recovery (Opt + Cmd + R.) To my surprise, macOS Sierra was listed as installation choice (probably the one that shipped with iMac.) Anyway, I tried it. But after quite a while, the installation failed and started showing a "question mark folder" during boot:

Installation attempt: Ventura via external bootable USB driver.

Afterwards, I created a bootable USB driver with the Ventura installer, as per Apple's instructions on the Support KB:

Create a bootable installer for macOS - Apple Support

I decided to perform a clean install. I erased my HDD (a 2 TB Fusion Drive) and formatted it as APFS (the recommended format.) However, this attempt wouldn't be any different from the first one: Installation stuck at some point, manual reboot, then stuck again... And all that after 4h of installation time.

Installation attempt: Big Sur via external USB driver.

This time, I tried to go back a few macOS versions and give Big Sur a try. However, I could't even try to install it, as it wouldn't connect to my Magic Mouse 2. As I don't have any other pointing device, I had to give it up.

Installation attempt: Monterey via external USB driver.

Same setup as above, but with Monterey. This time, I could proceed with the installation. I erased the HDD and checked it with Disk Utility's First Aid.

However, after a while, differently from the other attempts, the installation resulted in some errors that enabled me to dig deeper into the cause of the matter. I was starting to think that my HDD was defective.

"Storage system verify or repair failed (error 69716)" and no disk showing in the list of Startup Disks... See below:

Fixing a split Fusion Drive

After some research, I found out that in some cases, a Fusion Drive (hybrid HDD + SSD) can get split up and stop functioning as it should. So I rebooted the computer, booted from the external USB Monterey installation, and opened Disk Utility. Indeed, it showed two local storage devices: A 2 TB HDD and a 128 GB SSD.

Apparently, the contents of the said SSD can be erased without any trouble, as they're supposed to be recreated again by the OS, automatically. See:

How to fix a split Fusion Drive - Apple Support

So, as per the article above, I opened the Terminal and typed:

diskutil resetFusion

After a while, the two volumes were erased and the disk structure was recreated as APFS.

Installation attempt: Monterey via external USB driver (2nd time).

Again, I launched Monterey installation. It quickly reached the same point: "less than a minute remaining." Just like the other attempts, I left it there for a while. About 1h30 later, it finally finished the installation and the system booted up successfully!

Conclusion and key takeaways.

Do not turn off or reboot the computer, even if the installation seems stuck. Leave it there for 2 or 3h to make sure it is definitely faulty.

Also, check your target disk with First Aid in Disk Utility. It's not perfect, but can detect major faults.

Finally, make sure that your Fusion Drive is not split. If so, merge it again.

Consider a fresh, clean install instead of just reinstalling. It's much more time consuming, but can avoid some pesky issues. And always backup your data and system with TimeMachine.

* * *

I hope this article may help the thousands of people having the same problem, and that Apple might take a more serious look at this issue.