Quick update: I've tried using GRUB, and hit another snag. When I try to boot from the disk, it says something about the "ntfscomp" module not being loaded. After reading some man pages, I've tried re-installing GRUB with the "--modules=ntfs --modules=ntfscomp" arguments. (IDK if the former argument was really necessary, but I figured it couldn't hurt). Now, I have a proper boot menu, and am waiting to see if the drive finally boots. Oh, boy!

Darn it! I've tried booting into the flash drive twice, and both times gave me a kernel panic!

The only message currently on the screen that seems even remotely helpful is:
"Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(1,0)". Perhaps there's some parameter that GRUB needs to pass to the kernel to tell it to expect something other than FAT32?

I just noticed I neglected to post the link I referred to my earlier post so here it is.

https://help.ubuntu.com/community/Grub2/Installing

I'm not sure what you mean by 'tried using Grub'. What exactly did you do? The link below explains using Grub2 to directly boot a Linux iso file Grub by simply copying the iso file to a partition on your drive (hard drive, flash drive doesn't matter). Using this method, it doesn't matter if the iso is on a partition with a Linux filesystem, vfat, ntfs, etc.

https://help.ubuntu.com/community/Grub2/ISOBoot

The link below shows some example menuentries for Grub2.

https://help.ubuntu.com/community/Grub2/CustomMenus

I'm not really clear what you are trying to do and what you have available to use. If you want a persistent Ubuntu on a flash drive, unetbootin has always worked for me although I haven't tried it on 18.04. Do you have a Linux system available to use to create this? If you have an Ubuntu or derivative, other software that works well is mkusb which should be in the Ubuntu repositories. You can use dd to write the iso to a flash drive. There will be no persistence but that can be created from another Linux system. The only problem with this method is that you will need to add the word persistent to the linux line in grub.cfg on boot as well as manually mount the persistent casper-rw partition.

Do you have the iso on an ntfs partition? If so, you might want to add insmod ntfs to the menuentry. Do you have the iso on the partition or the extracted iso copied to it? Post your menuentry.tc

try passing the kernel parameter

When I said "tried using Grub", what I meant was I installed grub like so: sudo grub-install --boot-directory=/mnt/boot /dev/sdb --modules=ntfs --modules=ntfscomp. Since those modules are pre-loaded, there shouldn't be any real need to add them to the configuration file. PS: as it turns out, there's already a grub.cfg file, which is pre-configured already. So, I guess I don't need to set up a menu manually after all.

As for your suggestion of copying the ISO, I'll look into that.

As for unetbootin, that basically extracts the ISO to a FAT32 drive. That's pretty similar to what I'm trying to do, except for the FAT32 part. IDK about mkusb, as I've never heard of it. I guess I'll be looking into that, as well.

Also, I don't seem to have a menuedit.tc file. Is that used by legacy GRUB? I'm using GRUB2, so: guess I'll post my grub.cfg file, instead. See my attachment. On that note, I had to change the extension to .txt to upload it. The original name was (of course) grub.cfg.

I'm afraid that didn't have any effectat all.

Attached Files

grub.cfg.txt (953 Bytes, 10 views)

either ntfs driver isn't built into the kernel or initrd.img, or the root=ramfs parameter needs to be set in grub. Maybe boot the iso directly off the ntfs using grub. https://www.howtogeek.com/196933/how...ur-hard-drive/
https://www.linuxjournal.com/content/grub-boot-iso

Sorry about that, typo on my part. I meant the menuentries from grub.cfg which you have posted. The grub.cfg file you posted is the standard file with the entries one would expect to see on an Ubuntu "Live" CD/DVD or flash drive.

The command above should work IF you have an boot directory at /mnt/boot, IF it is writable which it would not be if you used pendrivelinux to create the bootable usb and if you mounted the partition on sdb(?) prior to running the command.

My experience with booting an iso file directly or extracted is that it makes no difference what the filesystem on the partition is as iso9660 will be used. I've booted an iso file directly from vfat and ntfs partitions without problems.

Might be simpler to start over and manually create a small partition with a Linux filesystem for a boot partition (1-200MB) then create another partition on which you can copy your iso file(s), install Grub2 and create your own grub.cfg file using the template you have posted and the examples for directly booting an iso at the link I posted earlier. Also, you should be able to boot the extracted iso if your bootloader is properly installed. You can do that from either Grub2 or Grub Legacy.