I ran into a problem that was caused by a missing leading slash (/) in the value of the file attribute of a disks source element. Defining the domain worked without a problem. Editing the domain and trying to save it resulted in a very generic error message: error: XML document failed to validate against schema: Unable to validate doc against /usr/share/libvirt/schemas/domain.rng Extra element devices in interleave Element domain failed to validate content Failed. Try again? [y,n,i,f,?]: It took me some time to find out that the schema defines in absFilePath a leading slash as required for a fully qualified file path but the C code parsing does not require/validate it. <define name="diskSourceFile"> ... <interleave> <optional> <element name="source"> <optional> <attribute name="file"> <ref name="absFilePath"/> </attribute> </optional> ... </element> </optional> </interleave> </define> <define name="absFilePath"> <data type="string"> <param name="pattern">/[a-zA-Z0-9_\.\+\-\\&amp;&quot;&apos;&lt;&gt;/%,:]+</param> </data> </define> I tried to fix the behavior by implementing additional validation code in method virDomainDiskSourceParse checking for the leading slash on the absolute file path. This resulted in breaking the VMware tests (xml2vmxtest), e.g. 8) VMware XML-2-VMX cdrom-scsi-file -> cdrom-scsi-file When looking at the related test data I found: <disk type='file' device='cdrom'> <source file='[testing] isos/cdrom.iso'/> <target dev='sda' bus='scsi'/> </disk> Besides the fact that the file path string also contains the characters space, opening and closing square brackets which are not specified as valid characters the file path string does not have a leading slash but instead some kind of 'datastore' specific name. What is the way to approach this since I am not a VMware user? 1) Change the schema to include the missing characters and removing the requirement for the leading slash and include additional schema aligned validation in the parsing code (method virDomainDiskSourceParse) or 2) fix the VMware tests to use absolute paths only and include additional schema aligned validation in the parsing code (method virDomainDiskSourceParse). -- Mit freundlichen Grüßen/Kind regards Boris Fiuczynski IBM Deutschland Research & Development GmbH Vorsitzender des Aufsichtsrats: Martina Köderitz Geschäftsführung: Dirk Wittkopp Sitz der Gesellschaft: Böblingen Registergericht: Amtsgericht Stuttgart, HRB 243294