Known issues

This article contains advisories and minor issues in the XenServer 8 release and any workarounds that you can apply.


  • When attempting to use the serial console to connect to a XenServer host, the serial console might refuse to accept keyboard input. If you wait until after the console refreshes twice, the console then accepts keyboard input. (CA-311613)

  • When read caching is enabled, it is slower to read from the parent snapshot than from the leaf. (CP-32853)

  • When attempting to log in to the dom0 console with an incorrect password, you receive the following error message: When trying to update a password, this return status indicates that the value provided as the current password is not correct. This error message is expected even though it relates to a password change, not a login. Try to log in with the correct password. (CA-356441)

  • If a XenServer host is powered off unexpectedly and restarted, when it attempts to recover VMs that had an attached vTPM, the vTPM can sometimes be missing from the VM. (CA-379928)


  • When NVIDIA T4 added in pass-through mode to a VM on some specific server hardware, that VM might not power on. (CA-360450)


  • If you attempt to live migrate a VM with dynamic memory control enabled to a target host where resources such as memory are very constrained, the migration can sometimes fail. (CA-380607)

Windows guests

  • For domain-joined Windows 10 VMs (1903 and later) with FireEye Agent installed, repeated successful RDP connections can cause the VM to freeze with 100% CPU usage in ntoskrnl.exe. Perform a hard reboot on the VM to recover from this state. (CA-323760)

  • When you create a UEFI VM, the Windows installation requires a key press to start. If you do not press a key during the required period, the VM console switches to the UEFI shell.

    To work around this issue, you can restart the installation process in one of the following ways:

    • In the UEFI console, type the following commands.

    • Reboot the VM

    When the installation process restarts, watch the VM console for the installation prompt. When the prompt appears, press any key. (CA-333694)

  • When attempting to update a Windows 10 VM from 1909 to 20H2 or later, the update might fail with a blue screen showing the error: INACCESSIBLE BOOT DEVICE. (XSI-1075)

    To make it less likely that this failure occurs, you can take the following steps before attempting to update:

    1. Update the XenServer VM Tools for Windows on your VM to the latest version.
    2. Snapshot the VM.
    3. In the VM registry, delete the following values from the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\XENFILT\Parameters key: ActiveDeviceID, ActiveInstanceID, and ActiveLocationInformation
  • When creating a Windows VM from a template that is set to not automatically update its drivers, the created VM is incorrectly set to update its drivers. To work around this issue, run the following command: xe pool-param-set policy-no-vendor-device=true uuid=<pool-uuid>. This command ensures that future VMs created from the template are correctly set to not automatically update drivers. VMs that were previously generated from the template are not changed. (CA-371529)

  • vTPM operations performed by the user or by Windows in the background might fail in the following situations:

    • If the toolstack or the XenServer host crash before the operation is synchronized to the disk. Errors when writing to disk are ignored.

    In the case of this type of failure the vTPM returns an error to the operating system. Windows logs these errors to the System Event log.

  • If you have Bitlocker enabled on a Windows VM and attempt to suspend or resume that VM, the VM can sometimes crash. (CA-368791)

    In addition, Bitlocker is not supported with VMs that have an attached vTPM.

Linux guests

  • You cannot use the Dynamic Memory Control (DMC) feature on Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Rocky Linux 8, Rocky Linux 9, or CentOS Stream 9 VMs as these operating systems do not support memory ballooning with the Xen hypervisor. (CA-378797)

  • On some Linux VMs, especially busy systems with outstanding disk I/O, attempts to suspend or live migrate the VM might fail. To work around this issue, try increasing the value of /sys/power/pm_freeze_timeout, for example, to 300000. If this work around is not successful, you can upgrade the Linux kernel of the VM to the latest version. (CP-41455)

  • If you install Debian 10 (Buster) by using PXE network boot, do not add console=tty0 to the boot parameters. This parameter can cause issues with the installation process. Use only console=hvc0 in the boot parameters. (CA-329015)

  • Due to a known issue with some SUSE Linux operating systems, if you attempt to trigger a crash dump on a SUSE Linux VM with 32 or more vCPUs, the operation fails and the VM does not restart automatically. This issue affects the following operating systems: SUSE Linux Enterprise Server 15 SP1, 15 SP2, 15 SP3, 15 SP4. (CA-375759)


  • When upgrading to or installing XenServer 8 from an ISO located on an IIS server, the install or upgrade can fail and leave your hosts unable to restart. The remote console shows the GRUB error: “File ‘/boot/grub/i3860pc/normal.mod’ not found. Entering rescue mode”. This issue is caused by the IIS configuration causing package files to be missing. To work around this issue, ensure that double escaping is allowed on IIS before extracting the installation ISO on it. (XSI-1063)


  • Non-ASCII characters, for example, characters with accents, cannot be used in the host console. (CA-40845)

  • In a Windows VM with XenServer VM Tools for Windows installed, copy and paste of double-byte characters can fail if using the default desktop console in XenCenter. The pasted characters appear as question marks (?).

    To work around this issue, you can use the remote desktop console instead. (CA-281807)


  • If you create a new installation of XenServer on a host with a local XFS SR on an NVMe device, your local storage does not attach on boot. The action fails with the error: “Raised Server_error(SR_BACKEND_FAILURE, [ FileNotFoundError; [Errno 2] No such file or directory: ‘/sys/block/nvme0n/queue/scheduler’ ])”.

    If you see this problem, contact us at feedback@xenserver.com. We are actively working on a fix that will be delivered in a future update. Ensure that you configure your pool to receive the latest updates.

  • If you use GFS2 SRs and have two hosts in your clustered pool, your cluster can lose quorum and fence during an upgrade. To avoid this situation, either add a host to or remove a host from your cluster. Ensure that you have either one or three hosts in your pool during the upgrade process. (CA-313222)

  • If you are using a GFS2 SR and your cluster network is on a non-management VLAN, you cannot add or remove hosts to your clustered pool. (XSI-1604)

  • After removing an HBA LUN from a SAN, you might see log messages and I/O failures when querying Logical Volume information. To work around this issue, reboot the XenServer host. (XSI-984)

  • You cannot set or change the name of the tmpfs SR used by the PVS-Accelerator. When the type is tmpfs, the command xe sr-create disregards the value set for name-label and instead uses a fixed value. If you attempt to run the command xe sr-param-set to change the name of the tmpfs SR, you receive the error SCRIPT_MISSING.

  • You cannot run more than 200 PVS-Accelerator-enabled VMs on a XenServer host. (CP-39386)


  • A limitation in recent SSH clients means that SSH does not work for usernames that contain any of the following characters: {}[]|&. Ensure that your usernames and Active Directory server names do not contain any of these characters.


For information about known and fixed issues in XenCenter, see XenCenter What’s New.

Known issues