This process was used to recover and reinstall macOS on a Late 2015 iMac stuck in a boot loop with no working GUI and no functioning internet recovery. Took a couple of hours, and included several failed attempts before success.
Overview:
Symptoms: Black screen, question mark folder, no macOS GUI.
Diagnosis: Corrupted system, internet recovery failed, no bootable system.
Initially I went to apple forums online to see on any potential areas that can help me. I read in many area's try internet recovery on mac. Soi thats exaclty what i did. cmd + r on a mac keyboard and alt r on a windows keyboard gets you to internet recovery on a mac.
I imediately went to disk utility and earased the disks and partioned them correctly.
Went to install macOS and it failed tried a bunch of times that day kept on getting the error "AN error occured while preparing the installation. Try running this application agaain"-- as many times as i retried this installation it conituend failing-- after that i read on a forum sometiomes these errors occur beacuse of the date --so in internet recovery i went tot terminal looked at the date by tyuping "date" and it was correct next step what reviewing the installation logs found a log something like " could not find startup disk" so i went back to reading and tryoing to find a solution --and that was create a bootable USB installer using the full createinstallmedia.
Key Notes & Common Issues
- Always Use Official Apple Installers Use the official Apple support site to download macOS disk images:
Apple macOS download links--- https://support.apple.com/en-in/102662 and https://support.apple.com/en-in/101578
Do not rely on Internet Archive versions. They often cause mounting or verification issues
- Partitioning & Volume Mount Errors One major recurring issue was the error: "Mount path is not valid" during createinstallmedia.
To check if your USB is mounted correctly:
ls /Volumes If your USB appears there, it’s mounted — but make sure:
It is formatted as Mac OS Extended (Journaled). - Very important!
The GUID Partition Map scheme is used.
- Use the Full createinstallmedia Command -- Terminal The shortened version often fails or gives permission/path errors.
Use this full format command (example for El Capitan):
sudo /Applications/Install\ OS\ X\ El\ Capitan.app/Contents/Resources/createinstallmedia
--volume /Volumes/MyVolume
--applicationpath /Applications/Install\ OS\ X\ El\ Capitan.app
--nointeraction --verbose
OR --verbose is highly recommended — it makes the installer "talk back" and show you real-time errors or progress.
- Installer Gets Stuck or Reboots to Wrong OS First Attempt Failed due to installing a version lower than the factory OS (Mavericks).
Always verify the original OS your Mac shipped with — using a version below this can block installation.
Afterward, macOS Sierra only worked from USB:
Without USB = no OS
With USB = Sierra booted live
Could not install until the disk was fully prepared and accepted the image.
Eventually, a bootable USB was created for Monterey from Sierra using the official Apple links — this was used to successfully upgrade the system.
- Installer Freeze ("Less than a minute remaining") Known Monterey bug.
Solution: Power off and power on once.
Installation will often resume or restart successfully on the next boot. -- 3 failed attemts later throughout the night --Monterey was installed!
- Disk Errors in Logs When reviewing logs during failed boots or installs, disk-related errors like:
"Could not mount disk"
"No valid target"
Typically caused by:
Incorrect partition scheme
Damaged or improperly formatted volumes
Fixed via Disk Utility or full disk erase/repartitioning.
Future Recommendations: Always keep a bootable macOS USB ready