Using Samsung T7 SSD as a bootable drive

Here is how you should go about installing the OS on an external drive:

1) Get yourself a USB3 thumb drive - it must be at least 16GB, probably better 32GB

2) Dowload the installer from the App Store. If it starts after downloading, quit the installer.

3) Follow the instructions here to make a bootable installer on the thumb drive:

How to create a bootable installer for macOS - Apple Support

4) Start your mac, and hold down Option key (in an intel mac) or keep pressing and holding the power button (Apple Silicon mac)

Choose to boot from the installer drive

5) Run Disk Utility from the installer, and erase the SSD - the whole drive, not just the volumes in it - as APFS with GUID

6) Quit Disk Utility and start the installation, choosing the SSD as your target drive.

7) (optional) when the installation is done, migrate the user accounts from the internal drive (do not migrate anything else; instead install fresh copies of your applications)

michawilson wrote:

It's a 2020 M1 mac mini running Monterey 12.6 and I'm trying to install the same OS onto the SSD.

Script is:

sudo /Applications/Install\ macOS\ Monterey.app/Contents/Resources/createinstallmedia --volume /Volumes/T5

So you were trying to make an installer disk on the same SSD in which you want to install the OS?

That is a bad move.

Get an inexpensive 32GB thumb drive, and create the installer on that.

Then boot your mac from the installer and use it to install Monterey on the T5.

Please open Disk Utility, go to View menu and make sure that Show All Devices is checked.

Then post a screenshot with the SSD drive selected.

michawilson wrote:

Hello Community,

I am having trouble formatting my SSD to use as a bootable drive. I've done everything right to erase, rename, select GUID Partition Map and format to APFS.

However, when I reboot the mac and attempt to run the installation of the OS, it says :

"This volume is not formatted as APFS"

So then I erase and retry all these steps again, open Terminal and run the script and it says:

"APFS disks may not be used as bootable install media" - and then it fails to erase.

Why is it so hard? What am I doing wrong?

What model and year Mac do you have? Your signature says Mac mini 12.1, is that correct? What year Mac? External booting is more straightforward for older Intel Macs, people trying that with newer silicon Macs have reported complications.

What MacOS are you trying to install on the external drive? 12.1? What MacOS are you running from on your current boot? 12.1? These things may all affect the success of what you are trying to do.

"open Terminal and run the script"

What script are you running?

Have you read this, it may be helpful:

Use an external SSD as your startup disk … - Apple Community

There are reports appearing on the ASC Forums regarding failed installation of Monterey on older Qualifying Apple Computers. In most cases this is related to having a NON Apple Original Internal Drive ?  

In your case the External Drive would fall into this Category

The EFI Boot ROM included in Monterey is verifying for Original Apple Drive and if not found , may Balk or fail to upgrade to Monterey. 

Reports indicate the EFI BOOT ROM is Required to Flash the Computer and is a  requirement for a Successful Monterey Installation.

Attempting to install Monterey to an External Drive, from observations on these Forums, is problematic at Best.

That does not mean impossible but . .

Aside - User profile is Mac mini, macOS 12.1

The current version is Monterey 12.6 as of this writing.

Change security settings on the startup disk of a Mac with Apple silicon

Have used the below script ( No Quotation Marks ) since Monterey 12.0.1 and every version there after successfully

" sudo /Applications/Install\ macOS\ Monterey.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled "

The Untitled at end of above script is the Name I gave it when I Pre-Formatted as APFS / GUID

If not working for your, Re-Format the Whole Drive as Fat / MBR and then re-format back to APFS / GUID.

This should destroy the Original Partition Map and lay down a New Partition Map

" 2014 iMac " Best it can run is Big Sur macOS 11

 How to get old versions of macOS 

michawilson wrote:

I'm trying to install Monterey onto an SSD to use with the same mac, which is a 2020 model with the M1 chip.

Why?

In theory, this is possible, but I have never seen so many people try to configure bootable external drives until Apple started shipping the M1 with those insanely fast internal SSDs. I can't get people with a 2017 iMac and a 33 MB/s mechanical hard drive to use an external SSD for booting. But people with a 2020 Mac and a 4500 MB/s will spend weeks on the effort to cut their hard drive speed by 95%. Why?

Maybe the OP can tell you why, in his case.

One possible reason: if you want to upgrade soon when Ventura arrives, but keep the option to boot into Monterey, just in case.

I do not have an M1 mac, but I am fully aware that an external SSD will be slower than the internal drive.

I still like to have a bootable clone in case something goes wrong. That is increasingly hard to do, but one way to achieve it involves first installing the OS, and then cloning the data portion. That way still works (for now).

Let me start by saying this as clearly and loudly as I can:

When you have any iMac from 2012 on, and the iMac only has an internal HD, it is a GREAT IDEA to install the OS on an external SSD and use it to boot your iMac.