Question 295694 in Docker Question posted in
The official documentation can be found here.

How to find which docker images that uses a specific overlay directory

Struggling with the lacking documentation at $DAY_JOB, I have figured out that I need to use one of our docker images that contain a specific *.so file. Let’s call it "libimportant.so".

A search with find reveals that the file exists in a local docker layer in my dev environment:

$ sudo find / -name libimportant.so 2>/dev/null
/var/lib/docker/overlay2/fedc8afc375f5bf02c74542b5d3a2621fcfd522875dff06bbb63fff6d1251234/diff/usr/lib64/libimportant.so

I have over 200 docker images locally (according to docker image ls | wc -l).

Question: How do I figure out which docker image (or docker images) that are using this docker layer?

NOTE: The environment currently has no containers running. This is a question about images, not containers.

I tried creating a container for each image, export the files, and search for the file in question. But this solution seems to take forever to run. It never run to completion.

$ docker image ls -qa | while read -r _hash; do _container="$(docker create "$_hash")"; docker container export "$_container" | tar t | grep -q 'libimportant.so' && echo "$_hash"; docker container rm "$_container" >/dev/null; done
^C
$

I also tried to list the GraphDriver data for each image, and grep for the overlay hash. But that didn’t find any matches.

$ docker image ls -qa | while read -r imageid; do docker image inspect --format '{{json .GraphDriver.Data}}' "$imageid" | grep -q 'fedc8afc375f5bf02c74542b5d3a2621fcfd522875dff06bbb63fff6d1251234' && echo "$imageid"; done
$

docker version

$ docker version
Client: Docker Engine - Community
 Version:           19.03.13
 API version:       1.40
 Go version:        go1.13.15
 Git commit:        4484c46d9d
 Built:             Wed Sep 16 17:02:52 2020
 OS/Arch:           linux/amd64
 Experimental:      false

POST EDIT

The reason I could not find the image was because my /etc/docker/daemon.json had reconfigured "data-root" from /var/lib/docker to another directory.

Therefore the layers in /var/lib/docker/overlay2 was not used by any image listed with docker image ls.

After correcting this, searching the GraphDriver.Data for each image actually worked.

Tags:

2

Answers


  1. Chosen as BEST ANSWER
    0

    As mentioned in my post edit, when I first tried to figure this out dockerd was using the wrong data-root.

    Here is my solution using GraphDriver that worked for me, pretty printed:

    layer_id="your_hash"

docker image ls -qa 
  | while read -r imageid; do
      docker image inspect --format '{{json .GraphDriver.Data}}' "$imageid" 
        | grep -q "$layer_id" && echo "$imageid"
    done

  2. 0

    You could do something like:

    layer_id="your_hash"

for img in $(docker image ls -aq); do
    if [[ $(docker image history --no-trunc | grep $layer_id) ]]; then
        echo "Layer found in $img"
    fi
done
    Login or Signup to reply.
Please signup or login to give your own answer.

Back To Top
Search