debug docker-squash

.gitignore

*.tar
docker/
dtest/
s/

README.md

Problem with docker squash not showing ancestors.

• Version reports

  docker --version
  Docker version 17.03.0-ce, build 3a232c8

  python --version
  Python 2.7.12

  lsb_release -d
  Description:    Ubuntu 16.04.1 LTS

  docker-squash @05cd17fe639183e2986fa89b3ddb62bcf903cf2b (1.0.4)

• I have a problem where docker squash produced images do not show correctly their ancestors with vizualition tools like nate/dockviz with docker >= 1.12.
  

• Indeed, they show up in the tree as having no ancestor despite the rootfs.layers properties.

• I was at first trying to determine if the produced image was still usable or if the loaded content from docker squash was leading to a corrupted image.

• Considering:

  • cat Dockerfile

    FROM alpine
    RUN touch fooa
    RUN touch foob

  • cat Dockerfile2

    FROM test1
    RUN touch 1a
    RUN touch 1b

• Then make a pdb inside docker-squash to have room to save the produced tarball for inspection and extract it somewhere for inspection

  venv/bin/docker-squash -v -t test3 -f test1 $(docker inspect test2 -f '{{.Id}}')
  (pdb) tar_file
  '/somewhere/x.tar'
  ^Z
  mkdir s
  tar xzvf -C s /somewhere/x.tar

• Prettyfying the jsons for inspection

  cat s/<SHA>.json         | python -m json.tool > s/<SHA>.json.pretty
  cat s/manifest.json      | python -m json.tool > s/manifest.json.pretty
  cat docker/<SHA>.json    | python -m json.tool > docker/<SHA>.json.pretty
  cat docker/manifest.json | python -m json.tool > docker/manifest.json.pretty
  

• Making 2 images of those dockerfiles

  docker build -t test1 . -f Dockerfile
  docker build -t test2 . -f Dockerfile2
  docker save test2 -o test2.tar

• Looking in the produced toplevel json file s/<SHA*>.json and diffing from what docker-squash/<SHA*>/json, we see at first that in docker squash json file:

  • container is lost
  • container_config is lost
  • Image has the form <UUID> and not sha256:<SHA>
  • history varies, but seems still valid and correlated as, ofc, we just rewrote a part with the tool.

2be38e2819619468fe1df5c8dfca4c929c0d557d1d93c9b785a7d4925ec66c68 sha256:23b9c7b43573dd164619ad59e9d51eda4095926729f59d5f22803bcbe9ab24c2 aafba8947124a6f67e5b588d5ff2b66e30b07f2cb1eff0974bbda004e14d65dd sha256:4eb0216f37e735ca2987fd0c31d8430ae746e736d3f5bab4b27bb41e3b08688c c632685499500acf92eee6754487c5b16fbef1dd44f6b34045a12479b933dbdc sha256:845cc8d94e6866379eb820bf9ef8281224bf55aa9fc8bb29ca71ff3ebb369d23 c638bf95e4e5d9d5a0f9e4a51594bedf0127b3b8c0fd053c6b0319161be53f37 sha256:7ab02dd6a21675fdabceb784f8fc35413c253a05f109eb5cb7529ba81b15d5df 29c416acbb1f9ee980b30c8c75b6abcf3b3ac791b4fad5d8df01754632dbdc09 sha256:d5e0577b12ae03578dd1e74241a03b7c5aeabe5bcc0973f161ab59d3eadef7f9 2d7b68975110379ced34847281b2fef1832dad03590644944a3634337f9783ca xxx sha256:3fd3aff183969e87645e19d0b3c4c684532fe9fd18b083594114775c3e91f45f

Dockerfile

FROM alpine
RUN touch fooa
RUN touch foob

Dockerfile2

FROM test1
RUN touch 1a
RUN touch 1b

Dockerfile3

FROM test3
RUN touch fooa