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I've got Ubuntu 10.04 installed on a computer and I am trying to do a fresh install of 12.04. I never had problems booting from a USB stick on it before and USB is setup as the first boot order in BIOS.

According to BIOS the USB stick is recognized at boot on the computer. And the USB stick works on another desktop computer I have tested it on.

Since I already have Ubuntu installed and I can access GRUB command line just after rebooting. Is there anyway I can manually get it to boot the USB stick from the GRUB command line or something similar?

I've tried both Startup Disk Creator and UNetbootin.

share|improve this question
Why not using regular method? – Anwar Shah Oct 14 '12 at 12:35
Because it doesn't work. Or by regular method, do you mean using a DVD? I would have tried that if I had a DVD player. – uvasal Oct 14 '12 at 13:18
Your title changed significantly. Are you now only interested in booting from iso file using grub2 (which you may have been referring to grub1) – Anwar Shah Oct 16 '12 at 5:25

You can boot the USB from grub prompt if you want. While you are on grub, press C to bring grub command prompt. Then type these commands. (I'm assuming your USB drive is /dev/sdb1).

linux /casper/vmlinuz file=/cdrom/preseed/ubuntu.seed boot=casper  quiet splash --
initrd /casper/initrd.lz

After typing the boot, hit Enter to boot from the USB. It should load the Live environment and you should install now.

You can also directly boot from the iso image without even extracting the files. Check this question below:

share|improve this answer
After the second line I get "error: no such disk". Also tried with /dev/sda1 and /dev/sdb. And I tried the link that you posted. I do not have Grub2 but it seemed to work, the install kicked in but then I got this error message "Could not find the ISO ubuntu.iso". But I am pretty sure it found it because one of the commands took a while to execute and I could only get it to work pointing to the ISO located on the USB stick. Not on the root of the file system (hd0,2 and hd0,1). Should I try to upgrade my Ubuntu 10.04 to Ubuntu 11.xx? – uvasal Oct 14 '12 at 15:03
You should put the usb and then reboot while it is still in the port. That is the only way for grub to recognize usb. for the second question, you need to use the actual iso name, not ubuntu.iso. For example, if your ubuntu iso is in /dev/sdb1 with name ubuntu-12.04-desktop-32bit.iso you should use that name. You may want to rename the iso file to a shorter name. – Anwar Shah Oct 14 '12 at 15:06
Yes I did rename the ISO to ubuntu.iso (like you suggested). And I am not sure what you mean by "put the usb and then reboot while it is still in the port". – uvasal Oct 14 '12 at 15:10
First insert the usb and then restart the pc without removing it from usb. – Anwar Shah Oct 14 '12 at 15:11
I never removed it. – uvasal Oct 14 '12 at 15:15

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