On old docker 1.8.x I’ve had:
root@node1:~# docker images | grep wiki docker.io/mprasil/dokuwiki latest d1dfbf6307fe 7 weeks ago 284.8 MB root@node1:~# docker inspect c4464ef30f1b | grep d1dfbf6307fe "Image": "d1dfbf6307fe54979ea7c167f8e369a6b6ae14ed25b9274523ed7859a355691a", "LowerDir": "/var/lib/docker/overlay/d1dfbf6307fe54979ea7c167f8e369a6b6ae14ed25b9274523ed7859a355691a/root",
whereas on docker 1.11.2 I see:
root@node1:~# docker images | grep wiki
mprasil/dokuwiki latest e71d9ced9728 7 weeks ago 284.8 MB
root@node1:~# docker inspect 986c2db0f344 | grep e71d9ced9728 "Image": "sha256:e71d9ced9728186af23e6929b0c5aee840f03cd083b7c25548425fc7dea26de6", root@node1:~# docker inspect 986c2db0f344 | grep Lower "LowerDir": "/var/lib/docker/overlay/10107ef441594695b93b42d34f24999a61af1a53eed3453487276c9dc1080a26/root",
As you can see on the old docker LowerDir was basically equal to Image id, whereas on the 1.11.2 it is not, and I can’t figure out what “10107ef” the id is. Can someone please clarify?
Official Docker docs seem outdated:
These four filesystem objects are all artifacts of OverlayFS. The “lower-id” file contains the ID of the top layer of the image the container is based on. This is used by OverlayFS as the “lowerdir”.
Side Note: somehow the same image (mprasil/dokuwiki:latest, pulled at the same time) has different IDs on docker 1.8.x and 1.11.2, but that doesn’t seem to affect me.