How to install a package in cirros image ?
I do not find any installer available in cirros image that comes along with devstack installation.
Answer
As @Harikrishnan commented, cirros does not include a package manager. Cirros is mostly useful to verify that clouds are working correctly, that VMs are started correctly and things like networks, security groups and key pairs are functioning as expected.
If you want a linux VM with a package manager, you should look at a different distribution. The Ubuntu cloud image is a good place to start - https://cloud-images.ubuntu.com/