If you want to use CentOS 7.1 for your hypervisors with Apache CloudStack and Ceph’s RBD as Primary Storage you need to rebuild libvirt.

CloudStack requires libvirt to be built with RBD storage pool support. It uses libvirt to manage RBD volumes. By default libvirt under CentOS is not built with this support. (On Ubuntu it is btw).

Rebuilding from source

First we need to install a couple of packages:

$ yum install -y rpm-build gcc make ceph-devel

Now we need to download the sRPM:

$ wget http://vault.centos.org/centos/7.1.1503/os/Source/SPackages/libvirt-1.2.8-16.el7.src.rpm

Create a rpmbuild directory:

$ mkdir /root/rpmbuild

Now edit /root/.rpmmacros so that it contains:

%_topdir    /root/rpmbuild

Install the sRPM:

$ rpm -i libvirt-1.2.8-16.el7.src.rpm

Open the /root/rpmbuild/SPECS/libvirt.spec file and look for:

%else
    %define with_storage_rbd      0
%endif

Change this to:

%else
    %define with_storage_rbd      1
%endif

Now build the RPM:

$ cd /root/rpmbuild
$ rpmbuild -ba SPECS/libvirt.spec

After a couple of minutes you should have RPMs with RBD storage pool support enabled!