How to Fix the ‘Couldn’t Modify Partition Map’ error on MacOS?

Sofie John
3 min readSep 28, 2021

Several users are complaining that they keep ending up getting the ‘Couldn’t modify partition map’ error on their system while triggering a re-format over partition by corruption. To repair this annoying issue, here are some potential fixes mentioned below.

Create a New Partition Map through Disk Utility

To create a new partition map via disk utility, follow these on-screen step by step instructions given below:

  1. Go to the primary dashboard of the macOS and launch the Finder application, then access your Utility folder.
  2. After going inside the Utility folder, twice click on the ‘Disk Utility’ option and wait for it to launch.
  3. Once opened the Disk Utility application, select the action icon of the application and keep in mind that the ‘Show all Devices’ option is turned on.
  4. Once you get the full devices list, you will be capable of choosing the suspicious device that’s causing the issue.
  5. Once it occurs, choose the device in question and right-click on it, then select the Erase button after adjusting the Format to MS-Dos (FAT).
  6. Then set the Scheme to Master Boot Record option.
  7. You have to wait until the partition map is chosen. You should get the same screen.

Create a New Partition Map from the Terminal Application

To create a new partition map from the terminal application, follow these on-screen step by step instructions given below:

  1. First, launch the Finder application via the action bar on the lower side of the macOS.
  2. After going into the Finder application, select the Go button and hit the ‘Utilities’ option via the context menu.
  3. You will get an entries list and twice click on the Terminal application.
  4. Later, input the following command to successfully detect the path of the drive that causing the error: diskutil list
  5. Once you get the devices list, insert the pursuing command after changing it accordingly to successfully clear the suspicious device in sort to reset the partition map: diskutil eraseDisk ExFAT *DeviceName* /dev/disk2
  6. Finally, redo the process that was earlier triggering the error and check whether the issue is solved or not.

Start a Repair Disk from Recovery Mode

To start a repair disk from Recovery Mode, follow these on-screen step by step instructions given below:

  1. Reboot the macOS conventionally and use the ‘Cmd + R’ while it boots up until you get the Apple logo.
  2. Once you view the logo, leave both buttons simultaneously.
  3. After going into the utility menu of macOS, select the Disk Utility option via the list of the available options.
  4. Then choose your affected drive that triggers the issue and select the ‘First Aid’ icon.
  5. At the verification pop-up, select the Run button to begin the process, then wait for the tool to complete checking the whole volume for errors.
  6. In case a problem is discovered, the tool will try to fix the issues over the volume itself.
  7. After completing the First Aid scan process, scroll down to the following procedure.

Restore the macOS Files to the Healthy State

To restore the macOS files to the healthy state, follow these on-screen step by step instructions given below:

  1. First and foremost, begin by ensuring that the flash disk or backup disk is linked to the Mac.
  2. Then select the Apple menu and choose the System Preferences option.
  3. After that, select the ‘Spotlight’ option via the list of the available options.
  4. You should select the ‘Migration Assistant’ option and select the ‘From a Mac, Time Machine backup, or startup disk’ option.
  5. Later, pursue further pop-ups to begin the process of restoring the healthy Mac state.
  6. Once finished, redo the earlier method causing the error and check the error.

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Sofie John

I am a content creator. I write blogs related to different news, updates, upcoming events, etc. I help my readers to keep updated with all recent happenings