I'm trying to install Ubuntu Server 18.04 on a PC with an old Intel motherboard. The installation finished ok, but at restart it says
no bootable device
I suppose that Ubuntu was installed in UEFI mode and the motherboard only boots in legacy mode.
What should I do?
There are three major breakpoints for processors. Non-pae/pae; 32-bit/64-bit; and BIOS/UEFI.
18.04 LTS will install in legacy mode. If you have the option in the BIOS to select UEFI then you will likely have a 64-bit processor and PAE.
If the OS installed in UEFI, then you can go into the BIOS and set the BIOS to boot from UEFI mode. Reboot. If booting still fails, you will have to set the UEFI boot target in BIOS. Hopefully, it will auto-detect it. If not, you will have to search for it using the utility in the BIOS. Without knowing more about the system, I can't really help you. The BIOS is very specific to the model of the computer.
If the computer is old enough to have either the first two issues, then the OS will not have even began the install.
My recommendation is to check the BIOS settings. If you are not going to use a hard drive more that 2.5 TB, then use legacy all the way around. On the boot-up, make sure that the boot-option you choose, matches your choice in the BIOS.
The standard Ubuntu 18.04 LTS Desktop and Server ISOs boot in both Legacy (BIOS) and UEFI, defaulting to Legacy (BIOS).
One other issue.... a dead battery will give you issues with booting.
Good luck!
