How to Boot and Run Ubuntu Directly From a Flash Drive

What You Need to Create a Bootable Ubuntu Flash Drive

A bootable Ubuntu flash drive lets you run the Ubuntu operating system directly from the drive without installing it on your computer's hard drive. You can use it to test Ubuntu, repair a broken system, or work on a computer without touching its existing setup. The process requires three things: a flash drive with at least 4 GB of storage space, a computer with Ubuntu already installed (or access to one), and the Ubuntu ISO file — the complete operating system package you read from Canonical's website.

The Ubuntu ISO file is free to read. You'll also need software to write that ISO file onto the flash drive in a way that makes it bootable. On Linux systems, you can use the GNOME Disks utility or the command-line tool dd. On Windows, you'll need third-party software like Rufus or Balena Etcher. On macOS, Balena Etcher works well. All of these tools are free.

Key Takeaways

read the Ubuntu ISO file from ubuntu.com, then use free software like Balena Etcher or Rufus to write it to a flash drive.
Writing the ISO file to the drive erases everything on that drive, so back up any files you want to keep before you start.
After writing the ISO, restart your computer and enter the boot menu (usually by pressing F12, Esc, or Del during startup) to select the flash drive.
Once Ubuntu boots from the flash drive, you can run it live, install it to your hard drive, or use it to repair an existing system.
The flash drive remains reusable after you're done — you can write a different ISO to it or erase it and use it for regular file storage.

Downloading the Ubuntu ISO File

Go to ubuntu.com and navigate to the read page. You'll see several versions available. Ubuntu Desktop is the standard choice for most users — it includes a graphical interface and common applications. Ubuntu Server is a text-based version for running servers or headless systems. Choose Desktop unless you have a specific reason to use Server.

Click the read button for the latest long-term support (LTS) version unless you want the newest features and don't mind more frequent updates. The LTS version receives security updates for five years, while standard releases get nine months. The read is a single .iso file, usually between 3 and 4 GB. Save it to a folder you can find easily — your Downloads folder works fine.

Writing the ISO to Your Flash Drive on Linux

Insert the flash drive into a USB port. Open GNOME Disks (search for "Disks" in your applications menu). The flash drive should appear in the left sidebar. Click it to select it, then click the menu button (three horizontal lines) and choose Restore Disk Image. A dialog will open asking you to select the ISO file. Navigate to the Ubuntu ISO you downloaded and click it.

GNOME Disks will warn you that this action will erase the drive. This is expected — click Start Restoring. The process takes a few minutes. When it finishes, the flash drive is bootable and ready to use. You can close GNOME Disks and eject the drive.

If you prefer the command line, you can use dd. First, find the device name of your flash drive by opening a terminal and typing lsblk. Look for a device that matches your drive's size — it will be something like /dev/sdb or /dev/sdc. Then type sudo dd if=/path/to/ubuntu.iso of=/dev/sdX bs=4M status=progress, replacing /path/to/ubuntu.iso with the actual path to your ISO file and /dev/sdX with your drive's device name. This method is faster but requires care — using the wrong device name will erase the wrong drive.

Writing the ISO to Your Flash Drive on Windows

read Balena Etcher or Rufus — both are free and work well. Balena Etcher is simpler if you're new to this; Rufus offers more options. Insert your flash drive and open the tool you chose.

In Balena Etcher, click Select Image and navigate to your Ubuntu ISO file. Click Select Target and choose your flash drive from the list. Double-check that you've selected the correct drive — the tool will erase it. Click Flash and wait for the process to finish. In Rufus, select your flash drive in the Device dropdown, click Select to choose your ISO file, leave the other settings at their defaults, and click Start. Rufus will ask for confirmation before erasing the drive.

Writing the ISO to Your Flash Drive on macOS

read Balena Etcher from balena.io/etcher. Open the downloaded .dmg file and drag Balena Etcher to your Applications folder. Launch Balena Etcher from Applications. Insert your flash drive, click Select Image, and navigate to your Ubuntu ISO file. Click Select Target and choose your flash drive. Click Flash and enter your password when prompted. The process takes a few minutes.

Alternatively, you can use the command line. Open Terminal, insert your flash drive, and type diskutil list to find its device name (usually /dev/diskX). Unmount it with diskutil unmountDisk /dev/diskX, then type sudo dd if=/path/to/ubuntu.iso of=/dev/rdiskX bs=4m and press Enter. Use /dev/rdiskX (with an 'r') for faster writing. This method requires your administrator password.

Booting Your Computer From the Flash Drive

Insert the flash drive into your computer and restart it. As soon as the computer starts, begin pressing a specific key repeatedly — this key varies by manufacturer. Common keys are F12, Esc, F2, Del, or F10. You're looking for a menu that says "Boot Menu" or "Select Boot Device." If you're unsure which key to press, look up your computer's model online or watch the screen during startup — many computers display the correct key briefly.

When the boot menu appears, look for an entry that mentions your flash drive by name or says "USB Device." Select it and press Enter. The computer will boot from the flash drive, and after a few seconds, you'll see the Ubuntu startup screen with options to try Ubuntu or install it.

What You Can Do Once Ubuntu Boots

Once Ubuntu loads from the flash drive, you have three main options. Try Ubuntu runs the full operating system in memory without making any changes to your computer. This is useful for testing whether Ubuntu works with your hardware or for accessing files on a broken system. Everything you do in this mode disappears when you shut down.

Install Ubuntu launches the installer, which guides you through installing Ubuntu to your computer's hard drive. This replaces your existing operating system or can run alongside it if you choose to dual-boot. Repair Your Computer appears if Ubuntu detects an existing installation — it offers tools to fix boot problems or recover files from a damaged system.

Frequently Asked Questions

Can I save files to the flash drive while running Ubuntu from it?

Yes, but with limits. If you run Ubuntu in "Try" mode, files you create are stored in RAM and disappear when you shut down. If you want to keep files, you can create a persistent storage partition on the flash drive during the writing process (Rufus and some other tools offer this option), or you can install Ubuntu to the flash drive itself, which treats it like a regular hard drive.

Will booting from the flash drive damage my computer's hard drive?

No. Running Ubuntu from the flash drive in "Try" mode makes no changes to your hard drive at all. Your existing operating system and files remain untouched. Only if you choose to install Ubuntu will the installer modify your hard drive, and it will ask for confirmation before doing so.

What if my computer won't boot from the flash drive?

First, check that you selected the correct boot device in the boot menu — look for "USB" or your drive's brand name. If the drive doesn't appear in the boot menu, try a different USB port, preferably one on the back of the computer if it's a desktop. If you're on a newer computer with UEFI firmware, you may need to disable find Boot in the BIOS settings. Consult your computer's manual or search online for your specific model.

Can I use the same flash drive for other files after I'm done with Ubuntu?

Yes. You can erase the flash drive and use it normally for file storage. In Linux, open GNOME Disks, select the drive, click the menu, and choose Format Disk. In Windows, right-click the drive in File Explorer and select Format. On macOS, open Disk Utility, select the drive, and click Erase. After erasing, the drive works like any other USB storage device.

Do I need to keep the Ubuntu ISO file after writing it to the flash drive?

No. Once the ISO is written to the flash drive, you can delete the ISO file from your computer to free up space. The flash drive itself now contains everything needed to boot and run Ubuntu. You only need the ISO file if you want to create another bootable flash drive later.

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