Trying to boot from macOS installer SSD, internet recovery starts instead

[miretogo]

Sequence of actions:

• I booted into the recovery mode and erased the Mac's (Mac Mini 2018) internal SSD.
• I created a bootable installer SSD with Install Disk Creator on another Mac (a MacBook).
• I attached the bootable installer SSD to the Mac Mini.
• I try booting from the bootable installer SSD by holding the option/alt key while booting.
• While I can select the bootable installer SSD in the boot menu a few seconds later, it stars internet recovery instead.

Why does internet recovery start despite the fact that I selected the bootable installer SSD?

 

[CoastalOR]

Your 2018 Mini has a T2 security chip that has a default of preventing booting from an external device unless the the Security Utility is used to set it to allow it.

Mac computers with the Apple T2 Security Chip - Apple Support

Learn which Mac computers have the Apple T2 Security Chip.

support.apple.com

About Startup Security Utility on a Mac with the Apple T2 Security Chip - Apple Support

Use Startup Security Utility to make sure that your Mac always starts up from your designated startup disk, and always from a legitimate, trusted operating system.

support.apple.com

Startup Security Utility on a Mac with an Apple T2 Security Chip

Startup Security Utility handles a large set of security policy settings for an Intel-based Mac with an Apple T2 Security Chip.

support.apple.com

 

[miretogo]

Thanks, that makes sense. However, when I press Command+R after booting to reach the Startup Security Utility (as suggested here: https://support.apple.com/en-us/HT208198), instead the Internet Recovery starts. What can I do now?

 

[CoastalOR]

Did you previously set the Security Utility to allow booting from a external device?

What was the purpose of erasing the internal SSD?

I have a 2018 Mini and I have not erased the internal SSD and have not experienced the problem you are having. I would use internet recovery to install macOS. Create an account then try booting to Recovery (cmd+r) and then launch the Security Utility.

 

[Fishrrman]

OP wrote:
"I booted into the recovery mode and erased the Mac's (Mac Mini 2018) internal SSD."

If you booted only to "the recovery partition", you DID NOT "erase" the entire drive.

To erase the ENTIRE drive, you need to boot to INTERNET RECOVERY:
Command-OPTION-R.

OK, I see you're getting tossed into internet recovery right now, so, here's what to do next:
- Open disk utility
- VERY IMPORTANT STEP: go to the "view" menu and choose "show all devices".
- NOW look to the list in disk utility
- The "topmost" line should indicate the PHYSICAL DRIVE inside -- THIS is what you need to click on and then erase
- Erase it to APFS with GUID partition format
- When the erase is done, close disk utility and open the internet OS installer.
- Now try installing.
- The Mini may reboot one or more times, and the screen may go dark and stay that way for a few minutes before continuing -- be patient
- When done, you should see the initial setup screen (choose your language)
- At this point, you can run setup assistant and restore from your backup, or start fresh...

 

[miretogo]

I erased the SSD because I want to sell the Mac Mini and wanted to make sure that all my data is deleted.

The problem with internet recovery is that it never finishes, it always gets stuck at some point.

Also, as a result of that, I can't reach Disk Utility or anything else.

 

[CoastalOR]

I'm not sure which OS you were using, but it must have been Mojave or later.

Here are the Instructions from Apple:
Are these instructions you were following?

What to do before you sell, give away, trade in, or recycle your Mac - Apple Support

Reset your Mac to factory settings to prepare it for a new owner.

support.apple.com

Are these the instructions you were using to erase?

Use Disk Utility to erase an Intel-based Mac - Apple Support

How to erase (format) the built-in startup disk of an Intel-based Mac.

support.apple.com

There is a way to revive the T2 firmware, but I'm not sure that is appropriate for your situation:

Revive or restore an Intel-based Mac using Apple Configurator 2

In rare circumstances, Apple computers may become unresponsive and the chip’s firmware must be revived.

support.apple.com

Going forward;
I would recommend you call Apple support for advice/assistance or make an appointment to take it in to a Apple store.

 

[miretogo]

Thanks, I will look at that. Is there any way to use Internet Recovery with Ethernet instead of WiFi? Even when I connect the Mac Mini directly to the router and disable WiFi, Internet Recovery still shows me only WiFi networks and gives me now option to select Ethernet.