安装grub2到U盘

Grub2 USB Flash Drive Install using the Ubuntu Live CD:

1. Boot from your Live Ubuntu Linux CD(不一定需要LiveCD，总之启动你的Linux系统)
2. Once booted, insert your USB Flash Drive
3. Open a terminal and type sudo su, or sudo -i
4. Type fdisk -l (and note which device is your USB)
5. Type mkdir /mnt/USB && mount /dev/sdx1 /mnt/USB (replacing xwith your actual usb device)
6. Type grub-install --force --no-floppy --root-directory=/mnt/USB /dev/sdx (replacing  x with your actual USB device)
7. 以下为建立grub.cfg，如果已有或者知道如何建立可以跳过
8. Type cd /mnt/USB/boot/grub
9. Type wget pendrivelinux.com/downloads/grub.cfg
10. Type df (and locate where cdrom is mounted I.E./dev/sr0)
11. Type dd if=/dev/sr0 of=/mnt/USB/ubuntu.iso (replacing sr0 with the device found in step 10)
12. Remove your Live CD and reboot your PC, setting your BIOS or Boot Menu to boot from the USB device.

If all goes well, you should now be booting into your Grub2 prepared USB Flash Drive, with a Grub2 Boot Menu option to Boot from the Ubuntu ISO you copied to your USB in step 10.

此文转载自：http://www.pendrivelinux.com/install-grub2-on-usb-from-ubuntu-linux/，中文部分是笔者加的。