GitHub user damien-kamerman created a discussion: Not able to attach iso - "is
not a valid QCOW2"
Hi,
I'm not able to attach an iso to a KVM instance. The error is 'The downloaded
file is not a valid QCOW2.'. It's definitely an iso and not a template so not
sure why it's checking for QCOW2. I'm using version 4.20.1.0.
What could I be doing wrong? Has anyone seen this?
Here's the error from /var/log/cloudstack/agent/agent.log:
2025-08-26 10:55:02,985 ERROR [kvm.storage.KVMStorageProcessor]
(AgentRequest-Handler-4:[]) (logid:) The downloaded file
[/mnt/61e67fa7-f26a-34d1-bc20-553a1b6ff798/deaa3e8b-2fcf-443e-80a4-dca3309bfafa.iso]
is not a valid QCOW2. java.lang.SecurityException:
[/mnt/61e67fa7-f26a-34d1-bc20-553a1b6ff798/deaa3e8b-2fcf-443e-80a4-dca3309bfafa.iso]
is not a valid QCOW2 because its first 4 bytes are not the QCOW magic string.
at
org.apache.cloudstack.storage.formatinspector.Qcow2Inspector.validateQcowMagicString(Qcow2Inspector.java:172)
at
org.apache.cloudstack.storage.formatinspector.Qcow2Inspector.validateQcow2HeaderFields(Qcow2Inspector.java:153)
at
org.apache.cloudstack.storage.formatinspector.Qcow2Inspector.validateQcow2File(Qcow2Inspector.java:81)
at
com.cloud.hypervisor.kvm.storage.KVMStorageProcessor.handleDownloadTemplateToPrimaryStorage(KVMStorageProcessor.java:2485)
at
com.cloud.storage.resource.StorageSubsystemCommandHandlerBase.handleStorageCommands(StorageSubsystemCommandHandlerBase.java:81)
at
com.cloud.hypervisor.kvm.resource.wrapper.LibvirtStorageSubSystemCommandWrapper.execute(LibvirtStorageSubSystemCommandWrapper.java:36)
at
com.cloud.hypervisor.kvm.resource.wrapper.LibvirtStorageSubSystemCommandWrapper.execute(LibvirtStorageSubSystemCommandWrapper.java:30)
at
com.cloud.hypervisor.kvm.resource.wrapper.LibvirtRequestWrapper.execute(LibvirtRequestWrapper.java:78)
at
com.cloud.hypervisor.kvm.resource.LibvirtComputingResource.executeRequest(LibvirtComputingResource.java:1958)
at com.cloud.agent.Agent.processRequest(Agent.java:779)
at com.cloud.agent.Agent$AgentRequestHandler.doTask(Agent.java:1194)
at com.cloud.utils.nio.Task.call(Task.java:83)
at com.cloud.utils.nio.Task.call(Task.java:29)
Thanks,
Damien
GitHub link: https://github.com/apache/cloudstack/discussions/11515
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