Kubernetes sets up a lengthy DNS search path, so any names are looked up multiple times. Adding a dot at the end tells the DNS resolver the name is absolute, and should not be tried against the search path. This will reduce pointless DNS lookups.
volumeMounts need to refer to an existing volume name to be successfully mounted. cri-socket is the defined volume name.
cri-o was used as an example as it is relatively easy to setup a cluster using that container runtime as compared to others.
