I've been given an old company laptop with a Windows 7 / CentOS dual boot setup - using MBR. I want to wipe the whole thing and install Ubuntu under UEFI - but I want to create my own partition layout (essentially, a normal layout with a second, unused 'root' partition to install a future new Linux distro into without trashing the live one).
So is it sufficient to simply choose 'manual', delete everything that's there, and set up the partitions I want? Will that also set up UEFI booting for me? I assume I also have to tweak the BIOS to boot off of UEFI - it's currently set to legacy. I'm typing from Ubuntu booted from a UEFI flash drive, so the BIOS can certainly handle it...
If it's not possible to do this in one step, can I just let Ubuntu 'take the whole disk' and then reinstall it after Ubuntu has done whatever magic it needs to do to convert to UEFI?
Don't over complicate this! It's easier if you start with a clean slate. Just format (erase) the disk prior to system installation:
When booting from Ubuntu installation media, choose the "Try Ubuntu" option.
Once you are in a live session, open the Disks application.
Choose your disk on the left side column and then click the hamburger menu on the top right of the window and choose "Format Disk..."
You can do a "Quick" erase and for "Partitioning" choose GPT.
(GPT is the partition scheme needed for UEFI installations)
Once the disk is formatted as GPT, reboot the computer for the system installation or just use the installation link on the desktop in the live session.
As long as you are booting in UEFI mode from your motherboard BIOS and not "legacy" or "compatibility" modes, and your disk has a GPT partition scheme, the installation will proceed as a UEFI installation.