How to get the list of dependent child images in D

Question

I'm trying to remove an image and I get:

# docker rmi f50f9524513f  
Failed to remove image (f50f9524513f): Error response from daemon: conflict: unable to delete f50f9524513f (cannot be forced) - image has dependent child images

This is the docker version:

# docker version
Client:
 Version:      1.10.3
 API version:  1.22
 Go version:   go1.5.3
 Git commit:   20f81dd
 Built:        Thu Mar 10 21:49:11 2016
 OS/Arch:      linux/amd64

Server:
 Version:      1.10.3
 API version:  1.22
 Go version:   go1.5.3
 Git commit:   20f81dd
 Built:        Thu Mar 10 21:49:11 2016
 OS/Arch:      linux/amd64

but there is no extra information:

# docker images --format="raw" | grep f50f9524513f -C3

repository: debian
tag: 8
image_id: f50f9524513f
created_at: 2016-03-01 18:51:14 +0000 UTC
virtual_size: 125.1 MB

repository: debian
tag: jessie
image_id: f50f9524513f
created_at: 2016-03-01 18:51:14 +0000 UTC
virtual_size: 125.1 MB

How can I get the dependent child images it claims to have?

there are no running nor stopped containers with that image id.

Answer 1

This is what I did in order to preserve my final "image" (layer, really - which is what threw me off, as I am just getting into docker builds).

I was getting the whole "... cannot be forced..." message. I realized I couldn't delete the images I didn't need because they are not really independent images created by 'docker commit'. My issue was, I had several images (or layers) between the base image and my final, and just trying to clean up is where I met the error/warning about the child and parent.

1. I exported the final image (or layer, if you will) out to a tarball.
2. I then deleted all the images I wanted to, including my final - I have it saved to a tarball so, while I wasn't sure if I would be able to use it, I was just experimenting.
3. I then ran docker image load -i FinalImage.tar.gz. The output was something like:

---

7d9b54235881: Loading layer [==================================================>]  167.1MB/167.1MB
c044b7095786: Loading layer [==================================================>]  20.89MB/20.89MB
fe94dbd0255e: Loading layer [==================================================>]  42.05MB/42.05MB
19abaa1dc0d4: Loading layer [==================================================>]  37.96MB/37.96MB
4865d7b6fdb2: Loading layer [==================================================>]  169.6MB/169.6MB
a0c115c7b87c: Loading layer [==================================================>]    132MB/132MB

Loaded image ID: sha256:82d4f8ef9ea1eab72d989455728762ed3c0fe35fd85acf9edc47b41dacfd6382

Now, when I list with 'docker image ls', I only have the original base image, and the final image I previously saved to a tarball.

[root@docker1 ~]# docker image ls
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
httpd               import              82d4f8ef9ea1        3 days ago          747MB
centos              httpd               36540f359ca3        5 weeks ago         193MB

---

My system is 'clean' now. I only have the images I want. I even deleted the base image without a problem.

[root@docker1 ~]# docker rmi 36540f359ca3
Untagged: centos:httpd
Untagged:     centos@sha256:c1010e2fe2b635822d99a096b1f4184becf5d1c98707cbccae00be663a9b9131
Deleted: sha256:36540f359ca3b021d4b6a37815e9177b6c2bb3817598979ea55aee7ecc5c2c1f

Answer 2

I've created a gist with shell script to print out descendant tree of a docker image, should anyone be interested in bash solution:

#!/bin/bash
parent_short_id=$1
parent_id=`docker inspect --format '{{.Id}}' $1`

get_kids() {
   local parent_id=$1
   docker inspect --format='ID {{.Id}} PAR {{.Parent}}' $(docker images -a -q) | grep "PAR ${parent_id}" | sed -E "s/ID ([^ ]*) PAR ([^ ]*)/\1/g"
}

print_kids() {
   local parent_id=$1
   local prefix=$2
   local tags=`docker inspect --format='{{.RepoTags}}' ${parent_id}`
   echo "${prefix}${parent_id} ${tags}"

   local children=`get_kids "${parent_id}"`

   for c in $children;
   do
       print_kids "$c" "$prefix  "
   done
}

print_kids "$parent_id" ""