Recently I installed Ubuntu on an USB drive, using my Mac Book Air.
Since then the following occurs from boot up:
- If the USB is inserted, the OS on the USB is loaded.
- 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.
- 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 ?