Install Ubuntu on a USB drive

Ubuntu is a popular Linux operating system, often used for embedded development. It’s possible to install both Ubuntu and Windows OS on the same machine, with Ubuntu files stored on a USB drive, managed by the GRUB bootloader.

However, in the current setup, the GRUB system and Ubuntu’s EFI files are stored on the PC’s internal disk.

Even when the USB drive is not plugged in, the GRUB system runs every time the computer restarts, allowing you to select the operating system.

To avoid this, I want to install the GRUB bootloader on the USB drive itself. This way, the GRUB system will only run when the USB drive is plugged in.

Install Ubuntu on USD drive

• Install Ubuntu desk

When installing Ubuntu, make sure to select the USB drive as the target installation location for Ubuntu. Additionally, ensure that your BIOS settings are configured to boot the Ubuntu GRUB, rather than the Windows Boot Manager.

Setting the BIOS to boot from the Ubuntu GRUB. Now, we can select either Ubuntu or Windows when the PC restarts. But the Ubuntu’s EFI files are stored on the disk of Windows.

Delete Ubutnu EFI on disk

The follwing steps do on WIndows.

• Run Diskpart
  • win+R: diskpart
• Check disk
  • list disk
• Select the disk saved EFI files of ubuntu.
  • select disk 0
• Check partition
  • list partition
• Select the system partition saved EFI files. In the windows, it is often in partition 1
  • select partition 1
• Assign the partition to p
  • assign letter=p
• Keep the running Diskpart
• Open notepad as administrator
  • Open folder on notepad
  • Go to the disk p and delete the ubuntu folder in EFI
• Back to the Diskpart
  • romove letter=p

Because we deleted Ubuntu's EFI files, there is no Ubuntu GRUB in the BIOS. When we restart the PC, it should boot to the Windows Boot Manager and run Windows.

Run Linux on USB drive

There are Windows Boot Manager and USB drive in the BIOS setting.

Check the linux boot files

• Set the BIOS to boot the USB drive
  • We get the GRUB system. Because there is no Ubuntu EFI, it cannot run Ubuntu automatically
• We need to set the Ubuntu in GRUB by command
• grub> ls can show the disk list
  • There are the disks and parts.
  • (hd0), (hd0, gpt1), (hd0, gp2)
• grub> ls (hd0,gpt2)/boot. There are vmlinuz and initrd in the /boot.

Boot linux

Set the path of vmlinuz :

grub> set root=(hd0,gpt2)
grub> linux /boot/vmlinuz-4.15.0-20-generic root=/dev/sda2

Notice the name of vmlinuz. /dev/sda2 is the diskpart in the Linux Identifier. (hd0,gpt2) is the diskparts in the GRUB Identifier

Set the path of initrd :

grub> initrd /boot/initrd.img-4.15.0-20-generic

Boot the Linux :

grub> boot

Then, We run the Ubuntu by GRUB.

Set GRUB on USB drive

Update GRUB :

sudo update-grub

Set Ubuntu's EFI in USB drive:

sudo mount /dev/sdX1 /mnt  # mount the EFI diskpart in USB drive
sudo mount /dev/sdXY /mnt/boot  # mount the Ubuntu root
sudo grub-install --boot-directory=/mnt/boot --efi-directory=/mnt --removable
sudo update-grub

Restart the PC and check if the Ubuntu GRUB exists in the BIOS. Now, we can select to boot the Ubuntu GRUB from the USB drive. Furthermore, when the USB drive is not plugged in, it will boot to the Windows Boot Manager and run Windows.