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

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Level 1

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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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Answer 1

Best reply

Grant Bennet-Alder

Level 10

128,335 points

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.

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Answer 2

Geotrax

Level 3

567 points

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

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Answer 3

hania00 Author

Level 1

4 points

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

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Answer 4

hania00 Author

Level 1

4 points

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

I'l have a go tomorrow - thanks for all the helpful replies

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

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