Linux: Installing Ubuntu on External SSD from ISO Image (Rufus)
How to install Ubuntu on an external SSD using an ISO image and Rufus, without modifying the host system.
I use Windows because SolidWorks and PSCAD are available exclusively for this system. These are fundamental tools for me.
Linux can be integrated into a Windows environment to varying degrees – from a tool layer to full system independence.
It can operate as:
- a tool layer (MSYS2)
- a subsystem (WSL)
- a virtual machine
- a system booted natively from a dedicated partition or a separate device (SSD, HDD, or even a USB flash drive).
The last option means a fully autonomous operating system. It runs without interfering with the host. One can experiment without risking damage to the main system.
In this article, I use Ubuntu as an example, but the described procedure applies to any Linux installation image in ISO format.
Installing Ubuntu on an External SSD (ISO + Rufus)
Below is a description of the installation process without modifying the host system.
1. Downloading the ISO Image
Download the Ubuntu Desktop image:
https://ubuntu.com/download/desktop
The recommended version is LTS (Long Term Support).
LTS refers to a release with long-term security updates and maintenance (typically 5 years).
Select binaries matching your processor architecture (e.g., x86_64 for a typical PC).
2. Running Rufus
Rufus is a portable Windows utility (no installation required) for creating bootable USB media from ISO images.
Project website:
3. Creating the Installation USB Drive
In Rufus:
- select the downloaded ISO file,
- partition scheme: GPT (for UEFI),
- file system: FAT32,
- write mode: ISO (default).
Create the bootable installation USB drive.
4. Launching the Installer
Restart the computer and enter:
- BIOS / UEFI,
- Boot Menu.
Select the USB drive as the boot device.
Start the Ubuntu installer.
5. Installing on the External SSD
The most important stage.
During installation:
- select the external SSD as the target disk,
- install the bootloader on the same external SSD,
- do not modify the system disk.
Result:
- External SSD connected → Linux boots
- External SSD disconnected → the main system boots
No interference with the host environment.
When using manual partitioning, ensure that system partitions and the bootloader are installed exclusively on the external SSD.
Partition vs SSD vs USB Flash Drive
The external medium can be:
Partition (shared bootloader, dual boot)
- does not require connecting an external device,
- modifies the main disk.
External SSD
- full independence,
- performance close to an internal drive,
- no interference with the host system.
USB flash drive
- limited flash memory endurance (write cycle count),
- low I/O performance,
- possible throttling under sustained load.
For development and embedded work, an external SSD is the most flexible solution.
Additional Note
As part of a Windows maintenance workflow (backup, system images), one can analogously prepare a Windows installation medium to restore the system from scratch.
This allows periodic “clean” system resets without data loss – provided that a proper backup has been made.
Summary
It is straightforward to install a Linux system (e.g., Ubuntu) on an external SSD from an ISO image using Rufus.
This allows safe experimentation with Linux at, for example, the driver or kernel level.
Connect the SSD → Linux boots.
Disconnect the SSD → the main system boots.
The host system can also be periodically restored from an image to return it to a clean state.
Clean and nice.