One of the quirks of booting from the DVD, is that this disc can boot either in EFI mode or in MBR mode.
Which of these actually happens may depend on the computer's firmware and/or the options it shows you and which you choose.
On the machine I normally use, the firmware is set to boot from a disc and shows me entries for both modes from which to choose. This really is a case of "your mileage may vary" and the variations of firmware settings and behaviours is beyond my (or anyone's?) ability to cover,
In short, you may need to be observant to be sure of what goes on when you boot the installer.
For booting from a thumb drive made from the disc ISO file - alas, by avoiding this I've not seen how/why/when it does which of the two modes.
Why did I have a step to remake the partition tables in GParted?
The short answer here is that I've never quite trusted whether the installer is running in EFI mode or MBR mode. But also on top of that, whether when it is told to use the whole drive for the install, will it reset the partition table type - i.e to GPT for the EFI install.
To be sure, the failing here is that the installer doesn't tell us exactly what it is doing.
Having done a lot of installs, I can sympathise about them having the right balance between selectable options and not being confusing.
I have found with the Ubuntu and Xubuntu installers, as long as they are running in EFI mode, and the target drive already has a GPT partition table, then the outcome is reliable.
What changes would I like to see made to the installer?
visual confirmation of which mode it intends to install with - EFI versus MBR
an ability to have it do the removable option for the GRUB install so I don't need to do that manually afterwards.
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Post Scripts
Some points added since the initial posting.
Booting the Installer disc in EFI or MBR mode
One of the quirks of booting from the DVD, is that this disc can boot either in EFI mode or in MBR mode.
Which of these actually happens may depend on the computer's firmware and/or the options it shows you and which you choose.
On the machine I normally use, the firmware is set to boot from a disc and shows me entries for both modes from which to choose. This really is a case of "your mileage may vary" and the variations of firmware settings and behaviours is beyond my (or anyone's?) ability to cover,
In short, you may need to be observant to be sure of what goes on when you boot the installer.
For booting from a thumb drive made from the disc ISO file - alas, by avoiding this I've not seen how/why/when it does which of the two modes.
Why did I have a step to remake the partition tables in GParted?
The short answer here is that I've never quite trusted whether the installer is running in EFI mode or MBR mode. But also on top of that, whether when it is told to use the whole drive for the install, will it reset the partition table type - i.e to GPT for the EFI install.
To be sure, the failing here is that the installer doesn't tell us exactly what it is doing.
Having done a lot of installs, I can sympathise about them having the right balance between selectable options and not being confusing.
I have found with the Ubuntu and Xubuntu installers, as long as they are running in EFI mode, and the target drive already has a GPT partition table, then the outcome is reliable.
What changes would I like to see made to the installer?