How can I write a Live USB for Kubuntu 22.04.2 that will boot in CSM/mbr mode?

Zeiss Ikon

3/18/24, 8:19 PM

I have a Thinkpad T430 that's been dual-booting successfully between Windows 10 and Ubuntu MATE 16.04 since a few days after I received it (purchased used on eBay around 2017).

The past two days I've been trying to install Kubuntu 22.04.2 over the MATE 16.04, and while I've managed to get the installer to complete, I can't get a boot to the GRUB2 menu, apparently because my USB key (written with either Ubuntu 22.04.2 Startup Disk Creator or dd from my working desktop machine with Kubuntu 22.04.2 only). This appears to be because my hard disk is formatted for mbr (CSM), but the USB key finished only as gpt, so boots in gpt mode. The USB won't boot if I set the laptop's firmware to Legacy Only; it will if I set to Both, either Legacy First or UEFI First, but in that mode, it writes the Kubuntu install in gpt mode, which won't boot from the mbr hard disk.

I've been told I should have an option during boot to select UEFI or mbr boot mode, "depending on the tool used to write the USB key" -- but I've seen no such option with either Startup Disk Creator (running on a desktop machine with only mbr on both platter drive and SSD) or dd created Live USB. There are no format options in either tool, as far as I'm aware; I wouldn't expect that from a block-by-block copy (that is, I'll get whatever boot sector is inside the .iso).

I did not have this problem on my desktop machine, but the USB I used for that install has gotten damaged and is unreadable. That install was Kubuntu 22.04.1, and I freshly downloaded Kubuntu 22.04.2 for this install -- and the file I used for the desktop machine is (safely) stored in the ~/Downloads folder on the laptop -- where I don't have access to it at present. Where can I find an mbr copy of the Kubuntu 22.04.2 .iso file, or alternately, what tool can I use to write a dual-mode USB key from the standard download?

0 + 7

live-usb

kubuntu

22.04

ubfan1

3/18/24, 10:46 PM

The standard ISO will boot both modes (UEFI,legacy) when just burned to an install media (dd). Which mode depends upon your machine settings, and disk partitioning will not force Ubuntu into any particular mode (That's a Windows requirement). You can boot UEFI mode on an MSDOS disk by having a primary(?) FAT partition with the boot,esp flags. Silly for a fresh install, but if you have existing things to preserve, works fine. (Did this for years on a W520)

Zeiss Ikon

3/19/24, 12:01 AM

@ubfan1 Yet, when I have a firmware setting to boot legacy only, my USB stick won't boot in my laptop!? And if it'll boot in either mode (and doesn't give me any options in "boot order" other than "USB Ubuntu HDD") how can I tell whether it's booted in CMS or gpt? And if that doesn't matter, why won't it boot to GRUB without the USB key?

ubfan1

3/19/24, 12:21 AM

To do a legacy boot/install, in UEFI settings select legacy before UEFI. The USB (from dd ing the ISO) will then boot legacy and install legacy. (Assuming the W520 UEFI settings are like your T430.). Again, gpt and MSDOS may boot either UEFI or legacy, with the appropriate partitions (grub-bios raw for a GPT legacy, and esp,boot flagged FAT EFI partition for either). Look in /sys/firmware for an efi dir with an efivars subdir for being in UEFI mode.

Zeiss Ikon

3/19/24, 12:22 AM

@ubfan1 I started with exactly that. Both, and Legacy First. My USB is still booting in UEFI mode. I've just run Ubiquity again, got through all the partition selection steps, and then got "No EFI System Partition was found. This system will likely not be able to boot successfully, and the installation process may fail."

ubfan1

3/19/24, 12:26 AM

Maybe better in chat or forum/install for this. Sadly, I fried my W520, so cannot try things out anymore.I hear a legacy install will still create an EFI partition, so uncertain what that error means.

Zeiss Ikon

3/19/24, 12:29 AM

@ubfan1 Well, I'm letting it run this time. It hasn't had an ESP for the past six-seven years. If it won't boot after, I'm exactly where I was, and if it will, I'll just add one more to the "stuff doesn't work the way Canonical says it should" file.

Zeiss Ikon

3/19/24, 1:15 AM

Okay, @ubfan1 -- even though I couldn't tell whether Live USB was running in EFI or mbr mode, it did finally work. All I had to do was ignore instructions. **NO** ESP, Windows partition flagged as 'boot', ignore the warning above, and let it run -- and after it completed, it started right up, perfect GRUB menu (I need to run `update-grub` to be sure it has Windows as an option; I don't use it but it's nice to have as a backup).

Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: How can I write a Live USB for Kubuntu 22.04.2 that will boot in CSM/mbr mode?

Post an answer

Most people don’t grasp that asking a lot of questions unlocks learning and improves interpersonal bonding. In Alison’s studies, for example, though people could accurately recall how many questions had been asked in their conversations, they didn’t intuit the link between questions and liking. Across four studies, in which participants were engaged in conversations themselves or read transcripts of others’ conversations, people tended not to realize that question asking would influence—or had influenced—the level of amity between the conversationalists.