On this page
“The USB will not boot” can describe several different failures. Start with the exact symptom. Change one thing at a time, then try again. Random firmware changes make the original cause harder to find and can stop Windows from starting.
Symptom: the USB is absent from the boot menu
First check that you opened the one-time boot menu, not only Windows or the firmware setup screen. Restart with the USB inserted and use the model’s documented boot-menu key. F12 is common, but Escape, F2, and F10 are also used; none is universal.
Then:
- Connect the USB directly to another port on the computer.
- Avoid a hub or dock during this test.
- Shut down fully, insert the USB, then power on and open the boot menu again.
- Confirm that the USB writer finished successfully rather than merely copying the ISO.
- Recreate the USB from the official completed ISO if its write status is unknown.
- Try another known-good USB drive when available.
If firmware never lists either USB, find the manufacturer’s official instructions for USB boot on that exact model. Do not copy another brand’s menu path.
Symptom: the computer starts Windows normally
This usually means the internal Windows drive stayed first in the normal boot order or no temporary USB choice was made. It does not prove that Ubuntu erased or changed anything.
Restart, open the one-time boot menu, and deliberately choose the USB entry. On a modern system, prefer the entry labeled UEFI for that USB. Do not permanently rearrange every boot device just to make one test.
If the USB was selected but Windows still starts immediately, recreate the media and verify that the ISO was written, not copied.
Symptom: Rufus reports failure
Record the exact message. Check that:
- The ISO download completed and optionally passes its SHA256 comparison.
- No file-browser or antivirus action is holding the USB open.
- The USB is connected directly and remains stable.
- Rufus came from its official site.
- The selected target has enough capacity for the current image.
Try another port, then another USB. Repeated errors on different USBs can point back to the ISO, permissions, port, or host computer rather than all the flash drives being bad.
Symptom: the USB appears but Ubuntu does not start
On modern hardware, select the UEFI entry rather than a Legacy or CSM entry. Canonical’s current Rufus guide documents GPT plus UEFI (non CSM) as a fallback when a modern machine fails to boot media made with the default Rufus result. Recreate the USB with that combination only after the normal write has failed.
If the screen displays a specific validation, signature, or security message, photograph or write down the exact text. Check the Ubuntu 26.04 release notes and manufacturer firmware documentation. Do not reinterpret a storage-controller message as a boot-media failure.
Symptom: a black screen appears immediately
Wait a short time once; initialization can take longer on some hardware. If the display remains blank:
- Confirm the same USB reaches the Ubuntu menu on another compatible PC when possible.
- Recreate and verify the media.
- Disconnect unnecessary displays and docks.
- Try the installer menu’s safe-graphics choice only if the current Ubuntu menu visibly offers it.
- Record whether a cursor, logo, or error appears and which graphics hardware the computer uses.
A black screen can have several causes, including graphics initialization. It is not enough evidence to disable Secure Boot or erase anything.
Symptom: only a Legacy or CSM entry appears
The USB may have been written with settings that do not match the system’s UEFI configuration. Recreate it using the documented GPT and UEFI fallback. Also verify that the firmware itself is operating in UEFI mode before changing compatibility settings.
Do not switch an existing Windows installation between UEFI and Legacy casually. Its boot configuration may depend on the current mode.
Symptom: Windows asks to format the USB
Cancel. After an image writer succeeds, Windows may not understand every Ubuntu partition. Formatting would remove the installation media you just created. This prompt alone is not a failure.
What about Secure Boot?
Ubuntu supports Secure Boot in ordinary supported installations. Do not disable it as a universal first step. Secure Boot becomes relevant when the screen gives a specific signature or security-policy error, when the hardware has unusual key configuration, or when official documentation for the exact release and model identifies it as the blocker.
If a temporary Secure Boot change is genuinely required by primary documentation, first record the original value and understand its effect on Windows encryption and hardware-backed Ubuntu encryption. Firmware changes can cause BitLocker to request its recovery key.
Recovery checklist
Return to a known state: keep the original ISO on the computer, recreate one USB with one documented writer, wait for its success status, eject it, and use the one-time UEFI boot entry. If that fails on two USB devices, collect the model and exact message before changing firmware.
Practice
Knowledge check
If Windows opens after power-on, name the first two checks: confirm that you opened the one-time boot menu, then deliberately choose the USB’s UEFI entry. Disabling Secure Boot is not the default answer.
What to learn next
Once the Ubuntu flow appears, continue to How to Boot Ubuntu from a USB Drive. If the media still fails after two controlled attempts, use the installation troubleshooting symptom guide to collect useful details for support.