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Appliance Installer Error: "An unknown error has occured"

KB ID: 4789
Product: Veeam Backup & Replication | 13
Published: 2025-11-10
Last Modified: 2025-11-10
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Challenge

When installing a Veeam Infrastructure Appliance on a physical or virtual machine using a bootable USB device created from the JeOS ISO file, the following error occurs:

An unknown error has occurred
Screenshot of the error that occurs within the JeOS installer.

Cause

This problem happens during installation, following the disk partitioning step, and is caused by an improperly created bootable USB drive.
Known Causes

The following methods for creating a bootable USB drive from the JeOS ISO have been known to cause problems:

  • Using Rufus with "Write in ISO Image mode."
  • Creating a bootable USB with Ventoy.
  • Other third-party bootable USB creation tools that don't write the image directly to the USB drive.

Note: Any method for making a bootable USB drive from the JeOS ISO other than the recommended Rufus "Write in DD Image mode," has not been tested or supported.

Solution

The recommended procedure for creating a bootable USB is documented in the User Guide.

It is recommended to use Rufus, and when prompted, select the non-default option to Write in DD Image mode:

Dialog box titled "ISOHybrid image detected" explains the difference between ISO Image mode and DD Image mode for writing an image. The option "Write in DD Image mode" is selected, with "OK" and "Cancel" buttons at the bottom.

Alternatively, instead of booting from a USB drive:

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