I just want to bring everyone's attention this important bug in Fedora 18. It looks like people are now starting to upgrade to F18 and are hitting this bug. https://bugzilla.redhat.com/show_bug.cgi?id=912499 In brief, when virt-manager runs, it starts some libguestfs instances in the background to inspect guests. Starting with Fedora 18 these use libvirt and because of a bad interaction between libguestfs & libvirt this causes the guest disks to get [SELinux] relabelled which suddenly prevents the guests from accessing their own disks. This will only affect you if SELinux is set to Enforcing. You may also see the same problem if you use read-only tools on running guests, such as virt-df, virt-inspector, virt-cat, etc., as root. There are two workarounds possible in the short term: (1) To continue using libguestfs to inspect disks, ensure the following environment variable is set everywhere: export LIBGUESTFS_ATTACH_METHOD=appliance (eg. by putting that line into /etc/profile.d/local.sh and logging out). Note that this disables sVirt protection in libguestfs, even if SELinux is enabled. (2) OR do: yum uninstall python-libguestfs This will disable the inspection features of virt-manager. I intend to fix the bug by modifying how it uses libvirt, and to push an updated libguestfs package to Fedora 18, but that will take a few weeks. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones virt-df lists disk usage of guests without needing to install any software inside the virtual machine. Supports Linux and Windows. http://people.redhat.com/~rjones/virt-df/