[Installation] Grub problems during dual boot installation, not the usual sda USB boot issue

[tailhappy]

Hello, I'm the new (old) guy. Short background, probably 15 years ago I had Kubuntu dual-booting and was living the high life. Back then Windows couldn't split route Cisco's VPN, and I was loving it.

Now have a new PC (post UEFI), got lazy and never set it back up to dual-boot. Finally got fed up enough again with Win10 that I want my Kubuntu back. Expected it to be easier before, but roughly 16 hours of trying to figure this out, I'm about to throw in the hat.

Should be super easy, I just don't understand the MBR or grub and only have a few hours to mess with it each night before I need to be sure Windows boots again. Made a fresh backup of everything with DriveImageXML, I'm sure that's outdated and would also appreciate any advice on how best to backup/restore a whole drive just in case.

PC is a fairly new Win10, sda is an SSD with Win10 installed, sdb is just an additional data drive. Disabled Secure boot, in Windows I re-partitioned to have space for ext4 root, and in trying to figure this out, have another partition for EFI too. The installer doesn't give me the option to dual boot, so I tried manual, assigning root and the EFI partitions. I've experimented with leaving the grub dropdown to just sda, and also tried sda6 which is the EFI partition. At the end of the install, I always get the "executing 'grub-install /dev/sda' failed." error. Ultimately have to boot back into the live DVD to set my boot partition back to sda1 to get to Windows again.

Should have gotten to this earlier, but I wrote the Kubuntu 20.04.1 ISO to a DVD, which seems to show up as sdc, so this isn't the issue where the USB boot drive is sda. That's the only solutions I've been able to find on the internet so far.

I'm fine with command-line live boot edits, at this point I just wanted to ask for help as I really can't afford to brick my Windows boot right now.

Really hated to post this since I'm sure the info is out there and I'm used to finding it myself. But at this point I don't have any more time to spend on it, and I'd really love to have Kubuntu again!

Appreciate any advice!

[tailhappy]

On the outside chance I was just making things hard on myself by being old school and writing the ISO to a DVD instead of USB, I created a bootable USB and tried again. Still no dual boot option, and after clicking Manual, the hard drive was still sda, and the same grub error. On the upside, at least the USB sure boots faster!

I hate not to use the SSD, but I have a data drive available too, sdb. I'm starting to think I might just need to try installing it there next. That's where the installer always defaults to. But grub would still need to update the bootloader on the SSD (sda), wouldn't it?

[jlittle]

... being old school and writing the ISO to a DVD instead of USB

IMO, using a DVD is old old school, and writing an ISO to a USB is old school. Again, strictly IMO, new school is iso booting with a USB set up with one of the mutibootusb projects, or something more pretty like Ventoy. (Even better, no USB at all, just iso boot from somewhere on an SSD, much faster; a little tricky if you want to install to the same SSD, but it works).

I hate not to use the SSD

It surely can be done. Firstly, be sure to understand the difference between the legacy BIOS/MBR boot and a UEFI boot, in that if you boot the USB in legacy mode, it can't do a UEFI install. How you choose which way the USB boots depends on the computer; mine presents several cryptic options when booting from a USB.

IMO you only want one ESP, the same one for Windows and Kubuntu. That's how UEFI is supposed to work.

I would use gparted from "Try Kubuntu" to create the partition or partitions you want for Kubuntu. I suggest running gparted and posting the layout of the SSD here on the forum.