Problem to start iMac after intall linux on dual boot with OSX 10.14 High Sierra.

[Herley]

Hello there.
Yesterday I installed Linux Ubunt dual with OSX (Mac) on my iMac 2009. when the install finished it froze the screen, I restart through iMac back button, but on restart it didnt boot either OSX or Linux, just stuck with a message:

APFSStart:1456: Mounting with apfs_efi_osx-748.77.8
efi_fusion_pairing:635: Container 59789fe8-145c-4af2-9cac-9d1ac677a2c8....................

Anyone have experienced something like that?
The problem is that Im stucked on this screen and cant access nothing through the keyboard. Basically I'm helpless...
Help!!!!!
Please...

Many thanks!

 

[Lufbrarunner]

How did you partition the drive when installing Ububtu? which boot manager is active is it the Apple one or Grub?

When I want to use a different OS on my mac I install it on an external disk and then boot into it by holding down the Option key at bootup, this method means I can avoid messing up the boot manager etc.

 

[Lufbrarunner]

After doing a little research it seems you may need to use an EFI bootloader.