Colors of Noise

Libvirt provides a lot of help to debug problems:

• it creates per virtual machine logfiles in /var/log/libvirt/ (when running as root) and ~/.libvirt/qemu/logs/ (when running as user). These contain the verbatim calls to QEMU/KVM so you can copy/paste them into the shell - you usually want to drop the -monitor pty argument then so you can access the QEMU/KVM monitor interactively (Ctrl-Alt-F2).

• running it verbosely in foreground mode is as easy as simply running libvirtd -v.

• if you do export LIBVIRT_DEBUG=1 before doing the above you'll get the very useful debugging output. I usally drop the -v then.

• also use the above export statement when debugging problems in virt-manager, virt-viewer or virsh but note that in the case of QEMU/KVM you'll end up calling into libvirtd with these tools so watching the daemon's debug output is more important.

• when debugging testcase failures in the source code export VIR_TEST_DEBUG=1 is your friend. Debugging a XML testcase failure then looks like:

  abs_srcdir=/your/path/to/libvirt.cvs/tests/ VIR_TEST_DEBUG=1 ./qemuxml2xmltest