Installing Red Hat Enterprise Linux 6 guest virtual machines with the Minimal installation option does not install the acpid package. Red Hat Enterprise Linux 7 no longer requires this package, as it has been taken over by systemd. However, Red Hat Enterprise Linux 6 guest virtual machines running on a Red Hat Enterprise Linux 7 host still require it.
Without the acpid package, the Red Hat Enterprise Linux 6 guest virtual machine does not shut down when the virsh shutdown command is executed. The virsh shutdown command is designed to gracefully shut down guest virtual machines.
Using virsh shutdown is easier and safer for system administration. Without graceful shut down with the virsh shutdown command a system administrator must log into a guest virtual machine manually or send the Ctrl-Alt-Del key combination to each guest virtual machine.
The QEMU guest agent runs inside the guest and allows the host machine to issue commands to the guest operating system using libvirt, helping with functions such as freezing and thawing filesystems. The guest operating system then responds to those commands asynchronously. The QEMU guest agent package, qemu-guest-agent, is installed by default in Red Hat Enterprise Linux 7.
CentOS is a Linux distribution that attempts to provide a free, enterprise-class, community-supported computing platform which aims to be functionally compatible with its upstream source, Red Hat Enterprise Linux (RHEL). Therefore, the solution basically are same.
Actually, we just need to install acpi daemon and qemu guest agent in ourguest and set the services start on boot.
yum install acpid qemu-guest-agent -y
chkconfig acpid on
chkconfig qemu-ga on
service acpid start
service qemu-ga start
Then, you can reboot your virtual machine gracefully now.