Client: Docker Engine - Community
 Version:           19.03.4
 API version:       1.40
 Go version:        go1.12.10
 Git commit:        9013bf5
 Built:             Thu Oct 17 23:44:48 2019
 OS/Arch:           darwin/amd64
 Experimental:      true

Server: Docker Engine - Community
 Engine:
  Version:          19.03.4
  API version:      1.40 (minimum version 1.12)
  Go version:       go1.12.10
  Git commit:       9013bf5
  Built:            Thu Oct 17 23:50:38 2019
  OS/Arch:          linux/amd64
  Experimental:     true
 containerd:
  Version:          v1.2.10
  GitCommit:        b34a5c8af56e510852c35414db4c1f4fa6172339
 runc:
  Version:          1.0.0-rc8+dev
  GitCommit:        3e425f80a8c931f88e6d94a8c831b9d5aa481657
 docker-init:
  Version:          0.18.0
  GitCommit:        fec3683

save and load image with tags correctly

you can try "docker save demo/demo:1.0 -o demo.tgz" .then "docker load -i demo.tgz"
Use the image tag to save the image and get the tag when loading.

I think this works if the tag was used at the time of saving, I can get the tag back. I am talking about the case whereby the tag was not used to save the image, but SHA was. In this case it will be great to have a way to tag the image while loading. That is what this feature request is about.

#dibs

@sandipchitale Can you please re-assign this task to me ?
I would like to work on it.

Hi @sandipchitale @AkihiroSuda. For clarity. Do you want a workflow like this?

1. I build a container with a tag:

docker build -t myapp:v1 .

2. Then I get images like this:

REPOSITORY          TAG                 IMAGE ID            CREATED              SIZE
myapp               v1                  76cfa8011d00        About a minute ago   803MB

3. I save the image with IMAGE ID

docker save 76cfa8011d00 -o myapp.v1.tgz

4. Load the image:

docker load -i myapp.v1.tgz

Current behavior after executed commands:

REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
<none>              <none>              76cfa8011d00        2 minutes ago       803MB

Expected behavior after commands executed:

REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
myapp             v1              76cfa8011d00        2 minutes ago       803MB

The name:tag should be specified explicitly like docker load -t myapp:v1 -i myapp.v1.tgz

I think if we will use -t flag with *.tgz file which contains two or more images (because save command can save more then one image to archive) we will get an error because we can't set one tag for different images.
Hmmm. But here we don't check error
@AkihiroSuda How should we do when one *.tgz file contains many images?

Maybe we should give up supporting this proposal then, and instead we should support docker load --format "{{json .}}" -i myapp.v1.tgz | some-external-script so that external shell script can handle untagged images

Maybe we should give up supporting this proposal then, and instead we should support docker load --format "{{json .}}" -i myapp.v1.tgz | some-external-script so that external shell script can handle untagged images

I think it's a good idea. But we can add -t flag only for one image in *.tgz and return an error or a warning when *.tgz contain more images.

@AkihiroSuda I found a better way. In the current workflow we have an image:

REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
customtag           v1                  bf756fb1ae65        4 months ago        13.3kB

If we save this image via a tag:

docker save customtag:v1 -o customtag.v1.tgz

And after we load this image from customtag.v1.tgz file. We got the image with the tag:

REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
customtag           v1                  bf756fb1ae65        4 months ago        13.3kB

I think need to save tags also when we save image via id(docker save bf756fb1ae65...) and restore tags when we make load command. And after this work user can run an external script for change default tags:

docker image list --format "table {{.ID}}\t{{.Repository}}\t{{.Tag}}\t{{.Size}}" | external-script

Multiple tags can refer to an ID though, so I'm not sure we should include all tags that reference that ID

Hmmm. I think we should include all the tags for one ID.
For example, I have an image with different tags and common IMAGE_ID. I saved my image via id:

docker save IMAGE_ID -o app.tgz

And when I load image from app.tgz I want to have same tags as before. Like:

REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
custom              v1                  bf756fb1ae65        4 months ago        13.3kB
hello-world         latest              bf756fb1ae65        4 months ago        13.3kB