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unable to do clean install of mojave on macpro mid 2012 - can't access boot manager

I have a mac pro mid 2012 - has been running Mojave successfully, but I want to do a clean install and find I cannot access the Start-up manager - I have no boot options.


I have the Mojave Installer on a flash drive - but am wary of formatting the ssd and then being unable to access it to boot from - I have tried over the last few days resetting PRAM, NVRAM, SSC etc etc as suggested online., but have got nowhere.


When I hold down Opt/Alt on startup - it either boots normally or not at all.


I have a bluetooth wireless keyboard.


The SSD is APFS formatted - some suggestions say that I need to format it to Mac extended journaled on erase...


Am at my wits end here - so any new suggestions would be great.


I have seen some comments that you cant access Boot Manager in Mojave...


I have used Disk Manager to check all my connected drives - all reported as ok.


I have a little knowledge of computers and am happy to have a try , (having been a programmer many years ago) - but am now out of my depth.


If I format the SSD will I still be able to access the connected flash drive and just run the installer that way?


Posted on Nov 12, 2021 1:52 AM

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Posted on Nov 12, 2021 4:45 AM

with a working graphics card present, insert the Bootable SSD and use:


system preferences > Startup Disk ...


... to set the SSD as the startup disk.

Shut down.

Restart, and you come up running from the SSD.


For those upgrading to a "no Boot screens" graphics card, a slight variation of this process also works if you need to swap graphics cards while the Mac is shut down. The boot drive is remembered in the Parameter RAM/NVRAM, as long as your PRAM backup battery is working, even after you remove AC power.

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Question marked as Top-ranking reply

Nov 12, 2021 4:45 AM in response to hania00

with a working graphics card present, insert the Bootable SSD and use:


system preferences > Startup Disk ...


... to set the SSD as the startup disk.

Shut down.

Restart, and you come up running from the SSD.


For those upgrading to a "no Boot screens" graphics card, a slight variation of this process also works if you need to swap graphics cards while the Mac is shut down. The boot drive is remembered in the Parameter RAM/NVRAM, as long as your PRAM backup battery is working, even after you remove AC power.

Nov 12, 2021 11:33 AM in response to hania00

Hi hania00,


The RX 580 is a PC graphics card that doesn't have a Mac capable ROM on it. That means that features such as the boot-picker and FileVault are unavailable. Grant presents a good idea, you can use the system preferences startup disk selection pane to set your install media as the default boot device.


Hope it helps!

-Geotrax

Nov 16, 2021 4:15 AM in response to hania00

Right - have managed it eventually.

A few issues along the way:

Initially I was unable to erase the APFS SSD holding the Mac os using Disk utility- kept saying 'failed".

This is apparently a known issue when doing a clean install of Mojave, on an APFS formatted SSD; I got over this by entering recovery mode and erasing it. (& formatting as APFS again)

However, when I then tried to instal Mojave from the Flash drive I got : Could not install a preboot volume for APFS Install.


After a bit of research, I went through the whole process again - having to reformat in Macos Extended journaled via recovery mode.

This time all went well, with restore from Time Machine working ok.

Thanks for all the help





unable to do clean install of mojave on macpro mid 2012 - can't access boot manager

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