An error when powering on Unitrends Virtual Appliance: Failed to start the virtual machine. Cannot open the disk. Failed to lock the file (affects UEB/UB)


No access to HTML5 /ui or Failed to start the virtual machine (UEB/UB).



1) Can not access the HTML5 /ui/ Web Administrative Interface (but the SSH Command Line Interface does work), and it is not the date and time of the normal Database Maintenance (usually Wednesday at 11am your time zone).

2) An error when powering on Unitrends virtual appliance Failed to start the virtual machine. Cannot open the disk. Failed to lock the file.


To correct the issue in either scenario:

  1. Use the SSH Command Line Interface to power off the Unitrends virtual appliance. For VMware or Hyper-v, you can alternatively use the Hypervisor Console for the Guest VM, and press the  ALT + F2 keys to drop to a Command Prompt. Once logged in, power off the VM using the command:    poweroff
NOTE:  For Unitrends Backup Enterprise, follow the instructions in "Shutdown or restart a Recovery Series appliance" to ensure proper shutdown is performed.
  1. Using the Hypervisor, edit the Unitrends virtual appliance and detach/remove (do not delete) any foreign virtual disks (those that belong to other Guest VMs), and keep track of their path just in case.
  2. Using the Hypervisor, verify that the snapshot removal process begins. If it does not, perform your standard snapshot removal and disk consolidation. Contact the Hypervisor manufacturer if you have any issues with the Snapshots/Change Block Tracking.
  3. Restart the Storage Device used for storing Unitrends Backups. In Unitrends Backup Enterprise, this storage also holds the Unitrends Database. Once the Storage Device is back online, verify that the storage device is healthy and resolve any hardware issues or backend file system errors exists.
  4. Once all issues have been resolved, restart the Unitrends virtual appliance. Monitor the Hypervisor presented Console for the Unitrends for messages. Once you see the Unitrends Console Interface come up, wait for five (5) minutes before using the HTML5 Web Interface to see if the issue is resolved.



This is caused by one of these two issues:

  1. The Unitrends virtual appliance has a foreign disks that is disrupting the ability to boot up.
If a communication error occurs (due to power event, network disruption, crash, storage latency, etc.), the message from the Unitrends Appliance to the Hypervisor that the HotAdd is no longer needed may not receive or sent. Power events can also cause storage to go offline, which could lead to data corruption. The result is that the Guest VM's continues to operate on a Snapshot while the primary virtual disk remains attached to the Unitrends Backup virtual appliance. This "foreign disk" left on the Unitrends virtual appliance may prevent Unitrends from rebooting
  1. There was a problem with power or communications (network, high latency), which caused a disconnect between the Storage Device and the Unitrends virtual appliance.
If a serious communication disruption or power event occurs, the Storage Device used for the backups and Unitrends Backup database may become dissociated from the Unitrends appliance. If the database is down, you will not be able to access the Unitrends Backup's HTML5 /ui/ Web Administrative Interface.
  1. The Storage Device is corrupted due to a hardware issue or power disruption.

    If this is the case, the data might not be recoverable and a redeployment would be required. If you are using UVB or PHD, please contact your Unitrends Representative who can work with you to obtain a Unitrends Backup Enterprise licensing.

    If you are already Unitrends Backup Enterprise, and you believe the issue is at the OS level, you can try to perform a Disaster Recovery of a UB that is using Stateless Storage (the Unitrends Database exists with the Backup data)

    If this does not resolve the issue, then a redeployment will be required. Use KB 5574 titled DEPLOYMENT: How to deploy the Unitrends Backup Virtual Appliance (AHV/Citrix/Hyper-v/VMware) do obtain all the documents, files, and instructions needed for a proper deployment using best practices.




In some environments where Hypervisor or Storage performance is less than optimal, this issue may occur more often. If you are using UEB/UB, you can disabled the HotAdd option, and default back to sending data over the LAN. If you wish to have this implemented, please open a new Support Case and have a Unitrends Engineer apply the resolution in KB 4539 How to disable hot-add as a transport method for vprotect.

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