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Fixing “EFI\BOOT\mmx64.efi not found” Error During Ubuntu 18.10 Installation on XPS 15

Ubuntu 5

The “EFI\BOOT\mmx64.efi not found” error is a common issue that users may encounter when trying to install Ubuntu 18.10 on a Dell XPS 15 laptop. This error is typically associated with the system’s UEFI firmware and the boot loader. In this article, we’ll explore several solutions to resolve this error.

Quick Answer

The "EFI\BOOT\mmx64.efi not found" error during Ubuntu 18.10 installation on XPS 15 can be resolved by renaming or copying the grubx64.efi file to mmx64.efi in the EFI boot directory. Enabling CSM/Legacy Boot or disabling Secure Boot in the BIOS settings may also fix the issue. Additionally, removing MokManager variables from the UEFI shell can help resolve the error.

Understanding the Error

The error message “Failed to open \EFI\BOOT\mmx64.efi – Not Found” typically appears when the system’s UEFI firmware can’t locate the mmx64.efi file. This file is a part of the MokManager utility, which is used for managing machine owner keys (MOKs) in a Secure Boot environment.

Solution 1: Renaming the File

One of the simplest solutions to this error is to rename the grubx64.efi file to mmx64.efi. This can be done in the /boot/efi or /efi/boot folder on the bootable USB drive. Here’s how to do it:

  1. Boot your system using a Live CD or USB.
  2. Open a terminal window.
  3. Mount the EFI partition of your bootable USB drive. For example, if your USB drive is /dev/sdb, you would use the command sudo mount /dev/sdb1 /mnt.
  4. Navigate to the EFI boot directory using the command cd /mnt/EFI/BOOT/.
  5. Rename the file using the command mv grubx64.efi mmx64.efi.

The mv command is used to move or rename files in Linux. In this case, we’re renaming grubx64.efi to mmx64.efi.

Solution 2: Copying the File

Another solution is to make a copy of the grubx64.efi file and name it mmx64.efi. This can be done using the cp command, which is used to copy files in Linux. Here’s how:

  1. Follow steps 1-4 from the previous solution to navigate to the EFI boot directory.
  2. Use the command cp grubx64.efi mmx64.efi to create a copy of the file.

Solution 3: Enabling CSM/Legacy Boot

In some cases, enabling the Compatibility Support Module (CSM) or Legacy Boot option in the BIOS settings can resolve this error. The steps to do this may vary depending on your specific BIOS, but typically involve the following:

  1. Restart your computer and enter the BIOS setup.
  2. Navigate to the “Boot” tab.
  3. Enable “CSM” or “Legacy Boot”.
  4. Save your changes and exit the BIOS setup.

Solution 4: Disabling Secure Boot

Secure Boot is a security standard that ensures that your computer boots using only software that is trusted by the PC manufacturer. However, it can sometimes interfere with the installation of Linux distributions like Ubuntu. Disabling Secure Boot can often resolve the “mmx64.efi not found” error. Here’s how:

  1. Restart your computer and enter the BIOS setup.
  2. Navigate to the “Security” tab.
  3. Disable “Secure Boot”.
  4. Save your changes and exit the BIOS setup.

Solution 5: Removing MokManager Variables

If Secure Boot is enabled and you encounter the “Failed to start MokManager” error, you can try removing the MokManager variables from the UEFI. This can be done by running the following commands from the UEFI shell:

dmpstore -d -all MokAuth
dmpstore -d -all MokNew

The dmpstore command is used to manage UEFI variables. The -d option is used to delete a variable, and -all is used to delete all instances of a variable. In this case, we’re deleting all instances of the MokAuth and MokNew variables.


The “EFI\BOOT\mmx64.efi not found” error can be a frustrating roadblock when installing Ubuntu 18.10 on a Dell XPS 15, but it’s usually possible to resolve with a bit of troubleshooting. Whether you’re renaming or copying files, adjusting BIOS settings, or managing UEFI variables, one of these solutions should help you get your Ubuntu installation up and running.

What is UEFI firmware?

UEFI (Unified Extensible Firmware Interface) firmware is a modern replacement for the traditional BIOS (Basic Input/Output System) firmware. It provides a standardized interface between the operating system and the computer’s hardware, including the boot process.

What is Secure Boot?

Secure Boot is a security feature in UEFI firmware that ensures the computer only boots using software that is trusted and digitally signed by the PC manufacturer. It helps protect against unauthorized or malicious software from running during the boot process.

How can I access the BIOS setup on my Dell XPS 15?

To access the BIOS setup on a Dell XPS 15, restart your computer and press the F2 key repeatedly until the BIOS setup utility screen appears. The specific key to access the BIOS may vary depending on your computer model, so refer to your user manual or Dell’s support website for more information.

Can I install Ubuntu 18.10 on a Dell XPS 15 without encountering this error?

While the "EFI\BOOT\mmx64.efi not found" error is commonly associated with installing Ubuntu 18.10 on a Dell XPS 15, it is not guaranteed to occur on every system. Some users may be able to install Ubuntu 18.10 without encountering this error.

Will renaming or copying the `grubx64.efi` file cause any issues?

Renaming or copying the grubx64.efi file to mmx64.efi should not cause any issues as long as the file is still located in the correct directory (/boot/efi or /efi/boot). The bootloader will still be able to locate and use the renamed or copied file properly.

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