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How To Fix “Failed to unmount /oldroot/dev” Warning During Shutdown or Restart in Ubuntu 20.04

Ubuntu 13

In this article, we will delve into how to resolve the warning message “Failed to unmount /oldroot/dev” that some users have encountered during shutdown or restart after upgrading to Ubuntu 20.04. This warning message is often accompanied by other similar messages relating to the unmounting of /oldroot, such as “/oldroot/dev/pts”, “/oldroot/dev”, and “/oldroot/sys”.

Understanding the Issue

Before we dive into the solutions, it’s important to understand what the issue is. The warning messages indicate that the system is unable to unmount these directories because they are busy. This could be due to a number of reasons, such as unused kernels or certain BIOS settings.

Solution 1: Removing Unused Kernels

One of the potential causes of this issue could be unused kernels. You can remove these kernels using the following command:

sudo apt-get autoremove --purge

This command removes all unused packages and configuration files. The --purge option is used to remove configuration files for packages that are no longer installed on your system.

Solution 2: Checking BIOS Settings

If you’ve recently switched motherboards, the issue could be due to certain BIOS settings. Here’s how to change these settings:

  1. Set “BIOS>Settings>Boot>Boot Mode Select [LEGACY+UEFI]” to “UEFI”
  2. Set “BIOS>Settings>Advanced>Windows OS Configuration>BIOS UEFI/CSM Mode” to “UEFI”

Please note that the exact steps may vary depending on your motherboard model.

Solution 3: Reinstalling the System

If the above solutions do not work, you may need to reinstall the system. While this is a more drastic step, it has been known to resolve the issue for some users.

sudo apt-get install --reinstall ubuntu-desktop

This command reinstalls the Ubuntu desktop system. The --reinstall option is used to reinstall packages that are already installed and at the newest version.

Conclusion

In this article, we’ve explored three potential solutions to the “Failed to unmount /oldroot/dev” warning message in Ubuntu 20.04. These solutions include removing unused kernels, checking BIOS settings, and reinstalling the system. It’s important to note that the exact cause of the issue may vary, and you may need to try different solutions to resolve it.

Remember to always back up your important data before making significant changes to your system. If you’re unsure about any of the steps, consult the official Ubuntu documentation or seek help from the Ubuntu community.

What does the warning message “Failed to unmount /oldroot/dev” mean?

The warning message indicates that the system is unable to unmount the /oldroot/dev directory because it is busy. This could be due to various reasons, such as unused kernels or certain BIOS settings.

How can I remove unused kernels in Ubuntu 20.04?

To remove unused kernels, you can use the command sudo apt-get autoremove --purge. This command will remove all unused packages and their configuration files. The --purge option ensures that the configuration files for packages that are no longer installed on your system are also removed.

What should I do if the above solutions do not work?

If the previous solutions do not resolve the issue, you may need to reinstall the Ubuntu desktop system. You can do this by running the command sudo apt-get install --reinstall ubuntu-desktop. This command will reinstall the Ubuntu desktop system, and the --reinstall option ensures that packages already installed and at the newest version are reinstalled.

Is it necessary to back up my data before attempting these solutions?

Yes, it is always recommended to back up your important data before making significant changes to your system. While the solutions provided should not cause data loss, it is better to be safe and have a backup in case of any unforeseen issues.

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