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Docker 1.11.2 GraphDriver (overlay) LowerDir logic change

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(Max Lobur) #1

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Official Docker docs seem outdated: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.

FYI I asked the same at http://stackoverflow.com/questions/37818504/docker-1-11-2-graphdriver-overlay-lowerdir-logic-change


(Max Lobur) #2

UPD: Docs are now up to date, however there’s still no info about the origins of IDs at /var/lib/docker/overlay/