I use emerge to check the status of ebuild, and I get this:
gentoo ~ # emerge -pv libvirt
These are the packages that would be merged, in order:
Calculating dependencies... done!
[ebuild R ] app-emulation/libvirt-0.9.10-r4 USE="libvirtd lxc nls policykit python udev -avahi* -caps -debug -iscsi -lvm -macvtap -nfs -numa -openvz -parted -pcap -phyp -qemu -sasl* (-selinux) -uml -virt-network* -virtualbox* -xen" 0 kB
The USE label avahi*, virt-network*, sasl*, virt-network* virtualbox* , what does the '*' mean in these labels. Thanks. I think these packages are already installed . Right?
Just look at man page: http://linuxreviews.org/man/emerge/ Everything is explain there.
'R' stands for: rebuild (specific version of package is installed already)
'*' stands for: change from/to enabled state' - If use flags changed, portage will prompt you to rebuild packages because the use flags might have a significant impact on package functionality.