Recover backup copy of a ubuntu linux installation on a usb stick using dd

I installed Ubuntu 10.04 on a usb stick in persistent install mode. So I could boot the laptop or my desktop computer with the stick, at boot time. Once I needed the 8GB stick for another purposes so I thought about coyping it to my desktop doing from mac os x:

dd if=/dev/disks3s of=/Users/jack/Desktop/usb_copy

Now I am trying to do the opposite, after having used the stick, which was formatted to NTFS, just doing

dd if=/Users/jack/Desktop/usb_copy of=/dev/disks3s

but although I can see that almost of the files are there, I can not boot again. IT is also strange the the file permissions are kind of strange, something like _user

What can I do ?

Thanks

Solution 1:

It's possible that you didn't copy the boot loader. If you don't have a boot loader your media is not bootable. You have to run the command "grub-install /dev/disks3s" to install GRUB (standard Ubuntu boot loader) on your USB stick.

The reason why you see strange permissions is that that every install of every OSes uses different user IDs. A user ID is used by the OS to identify users. Humans identify users by user name, and it can be the same in different systems, but the user ID is usually completely different. So another system can't decide which user ID means which user.