Can I boot an external SSD which is running a CCC clone then nuke and pave my Mac mini’s internal SDD?
Is it the same machine? Then yes.
However, be sure to verify that you
can boot from the clone (T2 chipped
machines need to be set BEFORE
you do this)
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I went into my Mac Mini boot recovery assistant (command-R). Actually did this several times - finally was able to erase the Mac Mini. Now will not let me install from bootable usb. I follow the instructions as noted in this dialog box. Each time this comes up after restarting with command-R, like “Groundhog’s Day”.
UPDATE - Now I have the ability to reinstall Mojave form the recovery partition. I guess I’ll have to do that, then install Catalina.
Any thoughts?
That will work too, or as @anon41602260 suggested, create
a separate installer (then you have it for future use.
You probably need to change your startup security settings. When you boot into recovery mode you’ll see the standard dialog box. Ignore that. Pull down the Utilities menu and you should see Startup Security. Select that and you’ll be able to select an option that will allow you to boot from your external drive.
Is it a 2018 (or later) Mini?
You have to change the security settings
Exactly. Sorry I’m dorking this url
But search for “Startup Security Utility”
Every time I did that I would get the same message as in the dialog box above. That is what have me perplexed. I am now reinstalling Mojave form the recovery partition. Just would not let me install Catalina from the usb thumb drive.
I could never get to that dialog box as shown in the link you just sent. Can’t really say how many times I rebooted the mini.
What happened to the CCC clone that we started with?
Change T2 settings to allow external boot, reboot, hold
down Option key, select clone; reinstall
To open Startup Security Utility:
- Turn on your Mac, then press and hold Command (⌘)-R immediately after you see the Apple logo. Your Mac starts up from macOS Recovery.
- When you see the macOS Utilities window, choose Utilities > Startup Security Utility from the menu bar.
- When you’re asked to authenticate, click Enter macOS Password, then choose an administrator account and enter its password.
What do you see when you first enter Recovery Mode?
Thanks for helping me with this. Yes, it really is frustrating. I was able to get to the startup security utility a couple of times, but it always eventually got me back to the dialog box suggesting the I restart with command-R. After I get Mojave up and running, I’ll try to get into the startup security utility and see what happens then. Will post then. Again, thank you all.
Oh! After you change your Startup Security settings and quit the utility, just Quit recovery mode and you’ll get to pick your startup disc.
Sorry @csf111, back over to you.
Here’s what happened: I was able to successfully install Mojave from the recovery partition. I rebooted with Command-R. Opened the Startup Security Settings and was finally able to authenticate and turn off the security setting allowing me to boot from an external drive. (was never able to do that before). Then when I went to open the thumb drive with the Catalina install, a dialog box came up saying that I couldn’t use the thumb drive as a startup disk because “the bless tool was unable to set the current boot disk”. I thought “oh, shiitake… here I go again”. But, I was able to reboot using the thumb drive to successfully install Catalina.
Thanks to @anon41602260 for the info on making the bootable Catalina installer and to @csf111 and @jec0047 for sticking with me through the process. I really appreciate it.
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Geez what an ordeal…
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Seriously 
HOWEVER, that’s what makes this forum great.
We all hung in there and @neonate continued
to do the work to make it happen.
I particularly like how on any given topic there
is feedback that effectively closes the item.
A rarity with current social media but reflective
of the early days. Great community
.
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