Kubernetes features quite a few types of volumes, including emptyDir:
An
emptyDirvolume is first created when a Pod is assigned to a Node, and exists as long as that Pod is running on that node. As the name says, it is initially empty. Containers in the pod can all read and write the same files in theemptyDirvolume, though that volume can be mounted at the same or different paths in each container. When a Pod is removed from a node for any reason, the data in theemptyDiris deleted forever....
By default, emptyDir volumes are stored on whatever medium is backing the node.
Is the emtpyDir actually mounted on the node, and accessible to a container outside the pod, or to the node FS itself?
Yes it is also accessible on the node. It is bind mounted into the container (sort of). The source directories are under /var/lib/kubelet/pods/PODUID/volumes/kubernetes.io~empty-dir/VOLUMENAME
You can find the location on the host like this:
sudo ls -l /var/lib/kubelet/pods/`kubectl get pod -n mynamespace mypod -o 'jsonpath={.metadata.uid}'`/volumes/kubernetes.io~empty-dir