On Wed, May 09, 2018 at 01:45:53PM +0800, Fei Li wrote: > 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 then compromise your disk images

> - 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 > 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.

Regards, Daniel