Comment 5 for bug 1334749

Hi George, hm, could it be that for the cases where that works libvirt had been installed after booting into Xen dom0? I had a quick look at the code we have in Trusty right now and the library code handling the URI basically checks LIBVIRT_DEFAULT_URI environment variable, or uri_default config variable, or falls back to qemu (in that order) [src/libvirt.c:virConnectGetDefaultURI]. This is the same as in the upstream git repo (pulled just now).
For virsh it seems looking only for the environment variable for a default or otherwise call the library with NULL which then again does the resoving as described above.

For UBUNTU (Trusty at least) the uri_default in the config file is commented out (so without anything in the environment defaulting to qemu sounds expected). Do you have something set (either in the environment or in the config file) for other distros?