Hi Daniel, On 05/09/2018 03:55 PM, Daniel P. Berrangé wrote:

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Hi,

When I do live migration using virsh command line based on NFS shared storage between two systems having the same security mechanism and having the same kvm/qemu/libvirt version, I encounter the following error:

debug : qemuMonitorJSONIOProcessLine:193 : Line [{"timestamp": {"seconds": 1524893525, "microseconds": 522686}, "event": "BLOCK_IO_ERROR", "data": {"device": "drive-virtio-disk0", "nospace": false, "node-name": "#block120", "reason": "Permission denied", "operation": "write", "action": "report"}}] ... error: internal error: qemu unexpectedly closed the monitor: qemu-system-x86_64: load of migration failed: Input/output error ...

According to the "Permission denied" && "write" information, I find the below 2 ways can fix this error: - Change the mode of guest's .qcow2 file from 644 to 646 Absolutely no - any process or user that can access the mount can

On Wed, May 09, 2018 at 01:45:53PM +0800, Fei Li wrote: then compromise your disk images Right, this should not be a fix. :)

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- Keep qemu's uid the same one between src host and dst host (They are not same before I change them) You *must* have the same uid+gid between source and dest hosts

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After confirming that keeping qemu's uid identical between src host and dst host can fix such issue, my question is whether a fix in libvirt should be pursued or just document the requirement for same uid:gid across host systems in a migration cluster is ok? In Fedora and RHEL at least the system is setup so that these users get a fixed uid:gid upon installation to avoid this kind of problem. Thanks for the "fixed uid:gid" advice, this helps a lot.

Have a nice day, thanks again Fei

Regards, Daniel