iMac: Error installing macOS Monterey on external SSD

jeffreythefrog wrote:

I thought the Mac needed Monterey to have been installed so that the EFI firmware could be updated for Monterey. is if the local drive has not previously been upgraded to Monterey at some point, (with the OEM drive) you cannot upgrade an external drive to Monterey. no?

You were correct. I was just adding one small detail that the internal SSD must have a valid Apple file system on it....the volume on the internal SSD can otherwise be empty at the time.

The internal SSD cannot be a blank drive with no partitions or file systems. Small detail, but can sometimes be the missing link for success or failure. I had installed a blank drive into a Mac which had no partition or file systems (or no valid Apple file systems) so the macOS installer refused to update the system firmware.

Sorry for the confusion. I was debating whether to add that information for your reference.

I also think the internal SSD must have a SMART status of "verified" (especially when installing Monterey).

duyu145 wrote:

So not every random SSD work and I need SSD from Apple to run Monterey externally?

Only the internal drive must be an Apple OEM drive and only when Monterey had never been previously installed on the computer. If Monterey was previously installed on this computer, then it should not matter whether the internal drive is an OEM drive or if it is even working (as long at the internal drive failure doesn't cause issues while booting from external media).

Apple doesn't make external drives.

The external drive can generally be any external drive that is compatible with Apple hardware which generally will be most name brands. The trick is to make sure to erase the whole physical external drive.....see my earlier reply with an Apple link with instructions.

Edit: Added bold italicized underlining to "installed" since it is possible to have Monterey running on a system without actually going through the install process. The install process is what updates the system firmware.

duyu145 wrote:

So not every random SSD work and I need SSD from Apple to run Monterey externally?

Whenever you try to install Monterey, it checks whether your Mac's firmware needs to be updated. If the installer thinks your firmware needs an update, it runs a firmware updater. That updater checks whether the internal SSD is an Apple OEM one. If it is not, the updater returns an error, and Monterey installation fails.

Once you have successfully installed Monterey anywhere, that implies that Monterey has done all of the firmware updating that it is going to do, so you can do any number of additional installations (internal or external) without it running the firmware updater that bombs out when it sees a non-Apple internal SSD.

So, if you are replacing the internal SSD … install Monterey somewhere first, then install your third-party internal SSD. Otherwise you'll have problems (re)installing Monterey anywhere (internal or external).

duyu145 wrote:

Yes, my internal HHD is running on Monterey. I also tried erasing both the internal and external with APFS and GUID partition Map Scheme. But it failed for the external SSD but was successful when installed on internal HHD.

You mean using Disk Utility to erase the external drive failed?

Did you erase the whole physical external SSD and not just the existing volume on it? See the following Apple article for details on erasing the physical external drive:

Erase and reformat a storage device in Disk Utility on Mac - Apple Support

If you did attempt to erase the whole physical drive, then what was the exact error message when it failed?

since we are discussing Monterey, is your local HDD already running Monterey? if not, that could be the issue. Monterey installs changed the boot software. if you try to install Monterey on the SSD without the local HDD being Monterey, it is likely to fail because that firmware update requires an apple OEM drive.

jeffreythefrog wrote:

if you try to install Monterey on the SSD without the local HDD being Monterey, it is likely to fail because that firmware update requires an apple OEM drive.

FYI, actually if Monterey has never been previously installed on a Mac, then the Monterey installer requires at least a properly formatted Apple OEM internal drive. The volume on the internal Apple OEM drive can be empty as long as it has a valid Apple file system on it (erased by Disk Utility).

I thought the Mac needed Monterey to have been installed so that the EFI firmware could be updated for Monterey. is if the local drive has not previously been upgraded to Monterey at some point, (with the OEM drive) you cannot upgrade an external drive to Monterey. no?

Did you format the external SSD using the GUID Partition Map scheme, and APFS?