Recently I installed Ubuntu on an USB drive, using my Mac Book Air.

Since then the following occurs from boot up:

  1. If the USB is inserted, the OS on the USB is loaded.
  2. If the USB is not inserted, and if the previous boot was as described in "1", the boot terminates in the grub shell waiting for a grub command. At this point, if I enter the command "exit", the shell is exited and my OS X is loaded.
  3. If the USB is not inserted, and the previous boot was as described in "2" , OS - X is automatically loaded.

I am using OS X Catalina 10.15.2. The USB has Ubuntu 18.04 TLS. I have an old Mac book air 2012.

I guess the UEFI is loading grub, and the grub cfg doesn't have the OS X entry explicitly. I didn't intend to make this change and don't know how to fix it.

I would like to have a boot menu appear. I would like the default OS to be OS X, and I would like to be given a timeout period to select boot from USB. I don't want to have to press the "option" key at boot.

Is this possible and if so how can I do this ?

  • 1
    What you want is exactly what the rEFInd Startup Manager can be configured to do. – David Anderson Jan 8 at 6:27

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