Hi,

I had a 1TB external HDD and I partitioned it with partition wizard. The first partition is of size 900 GB with all my data in it. I formatted the remaining 60-70GB and installed ubuntu on it. When I connected the external HDD to my laptop, the external HDD was recognized as /dev/sdb. The first partition was /dev/sdb1 and the second partition was /dev/sdb2. I formatted /dev/sdb2 as ext4 file system and installed ubuntu. During the boot loader installation, I selected /dev/sdb to install the grub boot loader. Everything worked fine up to this point.

However, when I reboot my laptop by connecting the external HDD, the control stuck at the grub rescue> prompt.

I did look at several forums, but it is more confusing when I look at the results.

Can some one help me? I have the super grub disk and boot repair disk, but haven't used them as I do not want to mess-up anything on the laptop as it is my work laptop.

On some page, I read that linux has to be installed on the first partition of the external hard drive and to have the data in the second partition. Can some one confirm?

Thanks,
Balaji.

Too little info.
Does the system boot ok without the external plugged in ?.
From a Linux system, even a liveCD, go here, run the script with the external plugged in and post the RESULTS.txt. That way we can see the boot environment.

did you also create a grub config file?
with e.g. you also have to take care into which partition that config file goes.
i think by default it goes into the /boot of the distro currently running.


i think you have to install grub to /dev/sda and then tell it to boot from /dev/sdb2.
Or, you have to tell your BIOS to boot from the external hard drive first.

Thanks for the responses.

@syg00: The laptop boots fine into windows with out the external HDD plugged in.

@ondoho: Sorry, I did not run the sudo update-grub after the installation. I don't remember doing this after every installation. I guess Grub installed fine with out any errors reported.

I don't want to install anything into /dev/sda as it is my work laptop.BIOS is set to boot from external hard drive.

Thanks,
Balaji.

Using the BIOS for an external with a modern linux...

I boot openSUSE 13.2 from my internal HDD, but installed Kubuntu in a logical partition of an external USB HDD. The bootloader for Kubuntu is installed in the logical partition of the external HDD.

When I use a keystroke to direct the BIOS to boot from the internal HDD, it finds the SUSE copy of GRUB2 and boots. When I choose to boot from a USB device, the BIOS finds the Kubuntu copy of GRUB2 with both Kubuntu and SUSE on the boot list.

In case your BIOS can't boot from a USB device, you can use the Plop boot CD.

https://www.plop.at/en/bootmanager/download.html

This might be the problem. Can you set the bios to boot from the internal drive and hit a key while powering up to select to boot from external drive?

As already mentioned, to find your bootloader...

This is a useful script to obtain information on what boots and where it is.

http://sourceforge.net/projects/bootinfoscript/

If you already have the boot repair software, run that and make sure you select the option to "Create BootInfo summary" and do not try to do any repairs. Post a link to the output here. It would have been useful if you had indicated which windows you have and whether it uses UEFI or not. This info will be in the boot repair output.