Welcome to the troubleshooting wiki page. We hope you'll find your problem here. Ideally, solution as well.

Determining version information, dealing with "unknown procedure"

The daemon cannot be started

Failed to connect to the hypervisor

Domain cannot be installed

The domain cannot be started when specifying different processor

Domain starting fails with Error "monitor socket did not show up"

Error "internal error cannot find character device" when trying to connect a domain's console

After import a guest from an existing disk image using virt-install, the guest starting stalls with "No boot device"

Creating VMWare ESXi domain failed with error "this function is not supported by the connection driver: virDomainCreateXML"

Virtual network 'default' has not been started

PXE boot (or dhcp) on guest failed

Guest can reach host, but can't reach outside network

Guest can reach outside network, but can't reach host (macvtap)

Could not add rule to fixup DHCP response checksums on network 'default'

Unable to add bridge br0 port vnet0: No such device

Guest won't start - warning: could not open /dev/net/tun ('generic ethernet' interface)

Common XML errors

Migration fails with "Unable to resolve address" error

Migration fails because disk image cannot be found

Migration fails under high load

No guest machines are present

Libvirt daemon is not listening on tcp ports although configured to

Libvirt identifies host processor as a different model from the hardware documentation

I created an external snapshot, but libvirt won't let me delete or revert to it