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Backup of VM on ESX server gives "Fault string: A specified parameter was not correct"

This article is only for Amanda Enterprise (AE) Issue Symptoms

    The following is found in the FAILURE DETAILS section of the Amanda backup report:

    • Fault string: A specified parameter was not correct.
    • deviceKey
    • Fault detail: InvalidArgumentFault
    • get-changeId failed: Couldn't determine changeId of this device key
    • CBT failed. Please reset CBT and then force a full backup

    Issue Description

    This is related to an image-level backup of a virtual machine on an ESX server and usually occurs when Change Block Tracking (CBT) is not being enabled for the VM being backed up. CBT is required by VMware's  vStorage APIs which are called by Amanda to perform the backup.  CBT is supported by virtual machine hardware version 7 or later and should be enabled by Amanda when the entry is added with a green check mark on the Backup|what page.


    First, make sure the VM is hardware version 7 or later as earlier versions do not support Change Block Tracking (CBT).

    If the VM is already at hardware version 7, you can verify if the VM is CBT enabled when powered off by checking for ctkEnabled entries in the Configuration Parameters section when editing VM settings. There should be one such parameter for the VM in general and for each of its virtual disk(s) as mentioned in the link above.  The value of each should be set to true. You can also use this perl script available at the VMware communities web site to verify if CBT is enabled and to enable or disable as desired.

    If CBT does not verify to be enabled for this VM, please enable and retry the backup.

    If the VM looks to already be enabled, try re-enabling to straighten out any wrinkle by following the CBT reset in this guide: VMware ESX Backup fails with fault detail "FileFaultFault"

    If backups are still failing, please use this guide Collecting Server Logs for Zmanda Support and contact support for additional assistance with this issue.