Description of problem:
When I opened the virtual machine manager, it raised a error: Virtual machine manager connection failure. The error message details as below:

unable to connect to '/var/run/libvirt/libvirt-sock', libvirtd may need to be started: No such file or directory

Traceback (most recent call last):
  File "/usr/share/virt-manager/virtManager/connection.py", line 1055, in _try_open
    None], flags)
  File "/usr/lib/python2.7/site-packages/libvirt.py", line 107, in openAuth
    if ret is None:raise libvirtError('virConnectOpenAuth() failed')
libvirtError: unable to connect to '/var/run/libvirt/libvirt-sock', libvirtd may need to be started: No such file or directory

Version-Release number of selected component (if applicable):
virtual machine manager 0.87

How reproducible:
Opened again

Steps to Reproduce:
1.open the virt-manger.
2.
3.
  
Actual results:
Can't use the whole function of the software.

Expected results:

no error.
Additional info: