grub is gone from my usb bootable device

[saume]

thanks for the help.

[yancek]

The first thing you need to do is try to understand what happened so it doesn't happen again.

Do you still have the Ubuntu iso file on your computer? If you do, you could create a mount point for it, loop mount and then copy the contents of the boot directory to your usb. If you don't know how to do this, post back.

You can install Grub to the usb with the following from the Ubuntu install. This assumes your usb is seen as sdb so you will need to run fdisk first to make sure that is correct. If not change it as appropriate. You will also need to create the test directory in the /media partition first. You will need to get the kernel and initrd files copied there also as the ones in the root of the system are just links, at least on Ubuntu 10.10.

sudo grub-install --root-directory=/media/test /dev/sdb