Unable to launch cirros instance
I am trying to launch a cirros instance and it's giving me the below error
Error: Failed to perform requested operation on instance "green", the instance has an error status: Please try again later [Error: No valid host was found. There are not enough hosts available.].
It means that none of the compute nodes in your cloud is able to run the Cirros VM, e.g. they do n't have enough capacity, or not the appropriate CPU, or many other reasons. Find more information in the Nova scheduler log file on the controller node, and the Nova compute logs on compute nodes.
Also check /var/log/libvirt/libxl/libxl-driver.log, this can help if nova-compute.log is not clear enough. This way I found out that xen VMs need a special kernel, or that my hypervisor was out of memory.