generic ISO-to-bootable-USB creator?

Nils Kassube kassube at gmx.net
Fri Sep 11 07:38:18 UTC 2015


Karl Auer wrote:
> Is it possible, and if so how, to create a bootable USB drive in Linux
> from a random (bootable) ISO?

I don't think it is possible for any random bootable ISO image. Usually 
a bootable ISO image which should reside on a CD/DVD would expect to 
read from a CD/DVD drive but a USB stick is something different, i.e. it 
is more like a harddisk. I think the image must have been created in a 
way which is meant to be run from either CD/DVD or USB stick.

> To my shame (or possibly my credit?) I
> have never in my life created a bootable disk for any operating
> system other than Linux! In this case however, the ISO concerned is
> actually a Linux ISO (generated by EaseUS), but I still can't make a
> bootable disk from it.
> 
> I tried just using dd to blat the image straight onto the drive;
> didn't work. There was a file system on the drive, and I could mount
> it OK, it was readable/writable etc and it contained the expected
> files, even though there were no partitions on the drive. But it
> would not boot.

I'm not familiar with EaseUS, but from skimming through their homepage, 
it seems to be a Windows application to manage partitions. Therefore I 
would expect it to write the contents of a partition to the ISO image. 
Then there is a file system and you can mount it but as it is the 
contents of a partition, you won't find other partitions in it. And of 
course it doesn't necessarily mean that it is bootable. Especially it is 
unlikely that they would create an ISO which is bootable independent 
from the wanted OS or that they would detect the OS and create the 
necessary boot code for that particular OS.

So if you want to make your USB stick bootable from the image of a 
partition which was bootable, you should first make the device contain 
an MBR. Then write a partition from your ISO and finally use GRUB to 
make it bootable.


Nils




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