I am trying to install an Ubuntu server on a Mid 2007 Mac Mini and erase OS X off of it. I formatted the USB properly on OS X Lion using the dd command, but when I went to the boot menu the only options were the main partition and the recovery partition. I have Ubuntu 18.04 server on the USB and Ubuntu 18.04 on a disc. The computer rejects any discs I put in though.
Well, your DVD drive does not appear to be working properly. So, I do not think you can use this drive to install Ubuntu. Also, your model Mac does not appear to allow EFI booting of the Ubuntu installation software from USB flash drives. Of course, there are applications such as Etcher and UNetbootin which might be able to create a bootable Ubuntu installer. I will assume you have investigated using these utilities and have already ruled them out.
The first question, which need to be answered, is how should Ubuntu Server boot. Below are the two possibilities with the high probability of success.
- Install Ubuntu Server to BIOS/GPT boot from the internal drive. Basically, Ubuntu Server would boot the same way Windows would boot.
- Install Ubuntu Server to EFI boot from the internal drive. Basically, Ubuntu would boot the same way OS X boots.
The next question is how to run the installer. Below are the two possibilities with the high probability of success.
- Boot the the installer in a virtual machine. The installer runs in the virtual machine, but the Ubuntu is installed to the physical internal drive.
- Run the installer from the internal drive. You will still need a virtual machine to copy installer files to the internal drive.
An example has already been posted here at Ask Ubuntu. See the question Installing Ubuntu without DVD or Flash Drive. Here, the objective was to BIOS/GPT boot 64 bit Ubuntu Desktop from the internal drive. VirtualBox was used to install the Ubuntu Desktop Live ISO files to the internal drive. Next, the Ubuntu Desktop Live was booted from the internal drive and used to install Ubuntu Desktop to the internal drive.
The above methods assume the use of a single machine. I should point out that the Mac can be put in target disk mode. You the could connect another Mac and run the installer there instead of using a virtual machine.