libvirt will only change the permissions for files it needs to, and only on demand. Therefore, it looks like i-4D8108F1, i-3E240779, and i-3DDB07C2 were all started after you changed qemu.conf and restarted libvirt. A reboot of the guest is not enough because a new qemu/kvm process is not launched. It looks like i-3878063D and i-44150778 (ie the ones with root:root ownership of the disk and console.log) were either rebooted or launched before libvirt was fully reloaded. i-4628084F is a mystery to me-- it certainly isn't anything libvirt did (libvirt doesn't know about the 'eucalyptus' user unless you configured qemu.conf to use it).
Carlos,
libvirt will only change the permissions for files it needs to, and only on demand. Therefore, it looks like i-4D8108F1, i-3E240779, and i-3DDB07C2 were all started after you changed qemu.conf and restarted libvirt. A reboot of the guest is not enough because a new qemu/kvm process is not launched. It looks like i-3878063D and i-44150778 (ie the ones with root:root ownership of the disk and console.log) were either rebooted or launched before libvirt was fully reloaded. i-4628084F is a mystery to me-- it certainly isn't anything libvirt did (libvirt doesn't know about the 'eucalyptus' user unless you configured qemu.conf to use it).