What is and isn't part of a pods ephemeral-storage?


I was curious what is and isn’t included in the pods ephemeral-storage? I know it’s described here. The issue though is it doesn’t necessarily specify the particulars.

For example if container images are stored in /var/lib/containerd/io.containerd.content.v1.content and the lowerdir, upperdir and workingdir of snapshotter are at /var/lib/containerd/io.containerd.snapshotter.v1.overlayfs. Then when those directories are mounted via overlayFS to something like run/containerd/io.containerd.runtime.v2.task/k8s.io/6fb87d2504f046f4cf5269e62ef7e4360baf0570b2acf8effcdd642/rootfs. If you do a du on that rootfs you will get a size that well appoximates the sum of the sub pieces. But overlayFS is supposed to layer things so that if all containers have a common base then it doesn’t duplicate space.

So my question is, when looking at ephemeral-storage. Is this full size found in run/containerd/io.containerd.runtime.v2.task/k8s.io/<hash> part of the ephemeral storage?

Looking at that directory

bash-5.1# pwd
bash-5.1# du -hs *
4.0K	address
296K	config.json
4.0K	init.pid
0	    log
0	    log.json
4.0K	options.json
1.8G	rootfs
4.0K	runtime
4.0K	shim-binary-path
0	    work

any tips or advice would be appreciated. Thank you.