Home > Questions

Disk Utility can't erase USB drive: Couldn't modify partition map

I want to reformat a USB flash drive that was previously used as a Linux boot device. When I plugged it into my Mac, I received a warning saying, "The disk you inserted was not readable by this computer." I then clicked "Initialize," which opened Disk Utility. Inside it, my disk was labeled as disk4s2. If I erase it, it fails with the error that says "Couldn't modify partition map." P.S. My thumb drive doesn't have a write-protect switch. Any idea about how I can fix it?

Best Answered by

iBoysoft author Jenny Zeng

Jenny Zeng

Answered on Monday, April 29, 2024

Instead of erasing the partition, try the physical disk.

Your external drive was a Linux boot drive, which means it has a partition map that's not readable on your Mac. Since your Mac can't modify the partition map, it can't erase the drive.

That's why you must erase the physical disk instead because it resets your drive with a compatible partition map. Follow the steps below to eliminate the "Couldn't modify partition map" error on Mac:

  1. Open Disk Utility.
  2. Click View > Show All Devices.
  3. Select the topmost level of your external drive and click Erase.
  4. Choose a name for your drive.
  5. Select a proper file system.
  6. Set the partition scheme to GUID Partition Map.
  7. Click Erase.

Did it work? If you still can't erase your USB stick on Mac, keep trying the methods in this guide:

How to Fix 'Couldn't modify partition map' on Mac (69874 & 69803)?

 

People Also Ask

Incorrectly-formatted external drive not mounting on Mac

Here are the steps to follow if your external drive can't be mounted after it's incorrectly formatted on Mac.

iBoysoft author Jenny ZengJenny Zeng

Command-X not working on Mac, why & any alternatives?

If the command-x can't cut files on Mac, read this thread to know how to fix it.

iBoysoft author Amanda WongAmanda Wong

HELP! My External drive used for Time Machine shows as uninitialized

This thread helps you to fix external hard drive uninitialized on Mac

iBoysoft author Amanda WongAmanda Wong

iMac boots to a circle with a line through it 🚫

Does your Mac boot to a circle with a line through it? Learn how to recover data from the unbootable Mac and reinstall macOS to resolve it.

iBoysoft author Jenny ZengJenny Zeng

How to fix external hard drive not mount?

It tells how to fix unmounted external hard drive.

iBoysoft author Eudora LiuEudora Liu

Can't select external drive to relocate Sound Library, help!

Read this thread to know possible causes and fixes for the Sound Library can't select the external hard drive to relocate content.

iBoysoft author Amanda WongAmanda Wong

Read More Questions

Read More Advice From iBoysoft's Computer Experts

Delete button not working on Mac

Delete Button Not Working on Mac/MacBook? 12 Feasible Fixes

This post covers all ways to fix the Delete button that's not working on your Mac or MacBook. Also, tell you why is the Delete key not working on Mac.

How to Tips

Permitir que los accesorios se conecten en macOS Ventura

[Corregido] macOS Ventura/Monterey no detecta el monitor externo

¿macOS Ventura no detecta el monitor externo? Aquí hay 9 formas de solucionarlo, también aplicable a macOS Monterey, Big Sur, Catalina.

Les disques durs externes se déconnectent sous macOS Sonoma

Le disque dur USB/externe se déconnecte-t-il régulièrement sous macOS Sonoma ?

Votre disque dur USB ou externe se déconnecte-t-il régulièrement après une mise à jour vers macOS Sonoma ? Voici 10 méthodes pour résoudre ce problème d'éjection automatique.