ShapeBlue Advisory on Libvirt 8+ Compatibility Issues with CloudStack



As of the 4.15 release, CloudStack has supported various EL8 operating systems / hypervisors, namely RHEL 8, CentOS 8, Rocky Linux 8 (and in theory – as of CloudStack 4.16 – all other EL8 variants including e.g. Alma Linux 8) – for both management servers and hypervisors. Similarly, support for Ubuntu 20.04 was added as of CloudStack 4.15, and OpenSUSE as of 4.16. All these Linux systems worked fine as hypervisors, until libvirt was upgraded to version 8+.

Effects on CloudStack

Historically, CloudStack used to set 22-character VNC passwords for KVM Virtual Machines, and libvirt was silently trimming it to 8 characters – and everyone was happy. But, with the latest libvirt changes (introduced in libvirt version 8, as explained here ) – libvirt will now throw an error and refuse to start or migrate a VM if its XML contains a VNC password longer than 8 characters. This would effectively be a deal-breaker for cloud operators and the only solution was to downgrade libvirt to an older (<8) version.

This affects CloudStack versions,,,,

Potentially affected Linux systems (some confirmed, some expected to be affected in near future or with Libvirt packages from external / enterprise repositories):

– All EL8 variants (RHEL 8, Rocky Linux 8, Alma Linux 8, CentOS 8)

– Ubuntu 20.04

– OpenSUSE 15.3 (and other SUSE variants expected)


ShapeBlue has released patches for both 4.15 and 4.16 LTS branches that fix these issues. These fixes are already available in the upstream Apache CloudStack project and have made into the release. The list of fixes that were made in these patches can be found here:

These 4.15 and 4.16 patches are available in ShapeBlue repositories, please refer to for usage. To apply these patches, use the ShapeBlue CloudStack repositories to upgrade packages on the management server and KVM hosts.

Further information

For ShapeBlue support customers, please contact the support team for further information. For other CloudStack users, please use the community mailing lists