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[Solved] grub cannot read usb drive's ext4 partition

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GNUser:
Hi Rich. I tried that after your tip and no luck.

As a last, desperate measure, I tried the  gdisk  and  mkfs  steps in Devuan. Lo and behold, the problem goes away.

My suspicion is that the  mkfs.ext4  step in TCL is silently failing to write some metadata to the usb stick. Without this metadata, grub cannot figure out the partition's filesystem and UUID.

I'd like to help pinpoint the problem. My preference is always to do everything in TCL.

jazzbiker:
Hi GNUser!
You may experiment with my grub4tc.sh, I never had problems with it. Still You will see a number of 'sleep 10' instructions in certain places.

GNUser:
I can confirm that this latest iteration of the USB stick (where I did  gdisk  and  mkfs  steps in Devuan) is booting just fine on my old BIOS laptop as well as on the new UEFI-only laptop.

I do have spare USB drives, of course, that I can use to troubleshoot this further.

patrikg:
Do you see the usb drive in grub ?
Or even grub need some driver to get to the usb drive ?
nativedisk ?

https://wiki.debian.org/BootUsbWithGrubRescue#Booting_a_flash_drive_with_an_image_file_written_to_it

GNUser:

--- Quote from: patrikg on February 07, 2024, 01:28:22 PM ---Do you see the usb drive in grub ?

--- End quote ---

Yes. When I run ls at the grub command prompt, I can see the laptop's internal SSD and its ext4 parition (hd0 and hd0,gpt1 respectively) as well as the USB drive and its ext4 partition (hd1 and hd1,gpt1 respectively).

grub can show me the contents of my internal SSD with ls (hd0,gpt1)/ but cannot show me the contents of the USB drive when I try ls (hd1,gpt1)/ because it errors out with "No known filesystem". Note that both (hd0,gpt1) and (hd1,gpt1) are ext4 partitions.

I am able to browse the USB just fine when I'm fully booted into TCL on my SSD (and various tools such as  gparted  and  blkid  can tell that the USB's first partition is ext4). grub seems to be the only program confused about the USB partition's filetype.



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