siddharth roy

Install Linux On External Drive The Best Way

Have you ever attempted to install Linux on an external drive, only to discover that while it boots perfectly on your installation machine, it fails to start on other computers? If so, you’re not alone. This common frustration stems from a widespread issue in Linux distribution installers that affects portability and can even modify your primary Windows installation.

In this comprehensive guide, we’ll explore why this happens and provide a reliable solution for creating a truly portable Linux installation that works across different machines.

The Problem: When Portable Isn’t Really Portable

When installing Linux on an external drive, users often encounter two significant issues:

  1. Limited Portability: The installation boots successfully on the machine used for installation but fails to boot on other computers
  2. Unintended System Modifications: Even when installing everything on the external drive, the main Windows drive and its bootloader may be modified, causing the system to automatically boot into GRUB with multiple OS options

These problems arise from a bug present in most Linux distribution installers, creating installations that appear portable but aren’t truly machine-independent.

Understanding the Technical Requirements

To successfully boot from an external drive, three critical requirements must be met:

1. ESP Partition Structure

The drive must contain an ESP (EFI System Partition) formatted with the FAT32 filesystem.

2. Bootable Flag Configuration

The ESP partition must have the bootable flag enabled, marking it as a bootable partition.

3. Proper Bootloader Installation

The ESP partition must contain a correctly named and configured bootloader.

The Root Cause: Installer Bug Behavior

During a typical Linux installation, users can specify where the ESP partition should be created—usually on the target drive. However, due to the installer bug, the software searches for existing ESP partitions across all connected drives. When it discovers an existing ESP partition (such as on your Windows drive), it installs the bootloader there instead of the selected location.

This behavior satisfies the first two requirements for the external drive but fails to meet the third, creating an incomplete portable installation.

Why Some Machines Boot While Others Don’t

Even after disconnecting the Windows drive during installation, you may find that the external drive only boots on the installation machine. This occurs because:

The NVRAM entry allows the installation machine to recognize the custom-named bootloader, but other machines without this entry cannot boot from the drive.

The Solution: Virtual Machine Installation Method

To create a truly portable Linux installation without modifying your primary system, use a virtual machine approach:

Step 1: Virtual Machine Setup

  1. Load your preferred Linux installer in a virtual machine
  2. Configure the VM to pass through the external drive
  3. Proceed with the standard installation process

This method installs Linux on the external drive with the bootloader contained within it, without creating any boot entries on your primary system.

For a detailed walkthrough of this process, you can reference this helpful YouTube tutorial.

Post-Installation: Fixing the Bootloader

After completing the virtual machine installation, you’ll need to address the bootloader naming issue to ensure universal compatibility.

The Solution: Using the –removable Flag

The key is to reinstall GRUB with the --removable flag, which:

Step-by-Step Bootloader Fix

Follow these commands to properly configure your bootloader (adapted from the Debian GRUB EFI Reinstall guide):

1. Mount External Drive Partitions

mount /dev/sdb2 /mnt/
mount /dev/sdb1 /mnt/boot/efi

2. Bind Mount Virtual Filesystems

for i in /dev /dev/pts /proc /sys /sys/firmware/efi/efivars /run; do sudo mount -B $i /mnt$i; done

3. Enter Chroot Environment

chroot /mnt

4. Reinstall GRUB with Removable Flag

grub-install /dev/sdb --removable

5. Generate GRUB Configuration

update-grub

Benefits of This Approach

By following this method, you’ll achieve:

Conclusion

Creating a portable Linux installation requires understanding the technical requirements and working around common installer limitations. By using a virtual machine for installation and properly configuring the bootloader with the --removable flag, you can achieve a truly portable Linux system that boots reliably across different machines.

This approach not only solves the portability issue but also maintains the integrity of your primary operating system, providing the best of both worlds for users who need flexibility without system modifications.