Unable to start VM on the host

[maic]

There is a host that cannot start or create VMs, while other hosts can start VMs normally. Cloudstack version 4.18, operating system: Ubuntu 18. The startup log error is as follows:

2026-06-26 10:16:38,552 WARN [resource.wrapper.LibvirtStartCommandWrapper] (agentRequest-Handler-5:null) (logid:bf3225ab) LibvirtException
org.libvirt.LibvirtException: internal error: process exited while connecting to monitor: 2026-06-26T10:15:36.570956Z qemu-system-x86_64: -drive file=/var/lib/libvirt/images/6969372f-70dd-47b5-9f0e-446955766ca5,format=qcow2,if=none,id=drive-virtio-disk0,serial=6969372f70dd47b59f0e,cache=none: 'serial' is deprecated, please use the corresponding option of '-device' instead
2026-06-26T10:16:38.428482Z qemu-system-x86_64: -drive file=/mnt/73dddfd4-e5e7-37d0-8db3-c8517789bf75/203-2-56edea15-0bbf-3feb-8b4f-49210b8dd0f5.iso,format=raw,if=none,id=drive-ide0-1-0,readonly=on: Failed to lock byte 100
at org.libvirt.ErrorHandler.processError(Unknown Source)
at org.libvirt.ErrorHandler.processError(Unknown Source)
at org.libvirt.Connect.domainCreateXML(Unknown Source)
at com.cloud.hypervisor.kvm.resource.LibvirtComputingResource.startVM(LibvirtComputingResource.java:2084)
at com.cloud.hypervisor.kvm.resource.wrapper.LibvirtStartCommandWrapper.execute(LibvirtStartCommandWrapper.java:104)
at com.cloud.hypervisor.kvm.resource.wrapper.LibvirtStartCommandWrapper.execute(LibvirtStartCommandWrapper.java:49)
at com.cloud.hypervisor.kvm.resource.wrapper.LibvirtRequestWrapper.execute(LibvirtRequestWrapper.java:78)
at com.cloud.hypervisor.kvm.resource.LibvirtComputingResource.executeRequest(LibvirtComputingResource.java:2116)
at com.cloud.agent.Agent.processRequest(Agent.java:662)
at com.cloud.agent.Agent$AgentRequestHandler.doTask(Agent.java:1082)
at com.cloud.utils.nio.Task.call(Task.java:83)
at com.cloud.utils.nio.Task.call(Task.java:29)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
at java.base/java.lang.Thread.run(Thread.java:829)
2026-06-26 10:16:38,712 INFO [kvm.storage.LibvirtStorageAdaptor] (agentRequest-Handler-5:null) (logid:bf3225ab) Trying to fetch storage pool 09fcf8c9-7c40-46ca-b18e-fb5df4ab03d9 from libvirt
2026-06-26 10:16:38,745 WARN [kvm.resource.LibvirtConnection] (agentRequest-Handler-2:null) (logid:bf3225ab) Can not find a connection for Instance i-2-115-VM. Assuming the default connection.
2026-06-26 10:16:38,818 WARN [kvm.resource.LibvirtKvmAgentHook] (agentRequest-Handler-2:null) (logid:bf3225ab) Groovy script '/etc/cloudstack/agent/hooks/libvirt-vm-state-change.groovy' is not available. Transformations will not be applied.

[DaanHoogland]

@maic , more context will be needed to investigate this.

• do you have any configuration differences amongst hosts?

as you mention 4.18, can you try adding the host to a newer version?

[maic]

The host configuration is the same, and this host was also able to start VM suddenly.
Due to special reasons, it is currently not possible to upgrade to a higher version. This issue has been encountered before. Previously, deleting the host and then adding it back in could create a startup VM. However, this time, adding the host again to create a startup VM still does not work