Software⏱️ 4 min read📅 2026-06-11

How to Fix: grub-install gives an error message I don't understand

GRUB installation error on CentOS 6.3 with USB drive

Quick Answer: The issue is likely due to the --root-directory option being used incorrectly. Try removing this option and see if grub-install works without it.

The error message 'More than one install_devices' when running grub-install indicates that the command is expecting a single device to install GRUB on, but instead, it's receiving multiple devices. This issue affects users who are attempting to install a Linux distribution from a USB drive using the grub-install command.

This error can be frustrating for new users as it requires them to re-evaluate their approach and understand the correct usage of the grub-install command. In this guide, we'll walk you through the root causes of this issue and provide two primary fix methods to resolve the problem.

🔍 Why This Happens

  • The primary reason for this error is that the grub-install command is expecting a single device to install GRUB on, but instead, it's receiving multiple devices. This can happen when the USB drive contains multiple partitions or file systems, causing the command to become confused. To resolve this issue, you need to ensure that you're installing GRUB on a single partition.
  • An alternative reason for this error could be due to the fact that grub-install is not able to determine which device to install GRUB on. This can occur when the USB drive contains multiple file systems or partitions with different mount points. In this case, you'll need to use the --root-directory option to specify the correct directory where GRUB images should be installed.

✅ Best Solutions to Fix It

Specify a single partition for installation

  1. Step 1: To resolve this issue, first, identify the correct partition on your USB drive that you want to install GRUB on. In your case, since you're using a vfat partition, you can use the following command: grub-install --root-directory=/mnt/usb /dev/sda1
  2. Step 2: Next, ensure that you've mounted the correct partition on the correct mount point. If you haven't done so already, run the following command to mount the partition: mount /dev/sda1 /mnt/usb
  3. Step 3: After mounting the correct partition, you can proceed with installing GRUB using the grub-install command.

Use the --root-directory option to specify the installation directory

  1. Step 1: If you're still experiencing issues after identifying the correct partition, try using the --root-directory option to specify the correct directory where GRUB images should be installed. You can do this by running the following command: grub-install --root-directory=/mnt/usb/boot --grub-shell=/mnt/usb/boot/grub/grub.cfg /dev/sda
  2. Step 2: In this method, you're specifying the root directory as /mnt/usb/boot and the grub shell file as /mnt/usb/boot/grub/grub.cfg. This tells grub-install to look for GRUB images in the boot directory of your USB drive.

🎯 Final Words

To summarize, the error message 'More than one install_devices' when running grub-install indicates that you need to specify a single partition or use the --root-directory option to resolve the issue. By following these steps, you should be able to successfully install GRUB on your USB drive and boot into your Linux distribution.

Did this fix your problem?

If not, try searching for specific error codes.

🔍 Search Error Database

❓ Frequently Asked Questions