Documentation: multiple tags by simply using multiple --tag parameters

[jonstelly]

I had cobbled together a build process using buildx where I ran buildx build ... --push twice (with different tags) so I could build and publish for multiple tags.

docker buildx build . --platform=linux/arm64,linux/amd64 --tag my/image:0.1 --pull --push --no-cache
docker buildx build . --platform=linux/arm64,linux/amd64 --tag my/image:latest

It didn't immediately jump out at me that the --tag parameter could be specified multiple times until I happened to see stringArray as the type for the --tag parameter. This lets me build and push to multiple tags in one step:

docker buildx build . --platform=linux/arm64,linux/amd64 --tag my/image:0.1 --tag my/image:latest --pull --push --no-cache

I'll try and find a minute to add this to the README.md and submit a PR in the next couple days but wanted to capture this as an issue to explain it first.

[timorkal]

Please +1

[yywing]

Is it work? My test is not work.
#459

[ksurl]

does this work for different registries in the same command? e.g. tag and push to docker hub and github container registry

docker buildx build . --platform=linux/amd64 -t user/image -t ghcr.io/user/image --push

[immanuelfodor]

Yes, it does, I'm actively using it in my CI to publish to an internal registry and DockerHub simultaneously: https://github.com/immanuelfodor/kube-karp/blob/master/.drone.yml#L59

[crazy-max]

https://github.com/docker/buildx/blob/master/docs/reference/buildx_build.md#options

[dudicoco]

@crazy-max according to the docs --tag accepts a stringArray, however when attempting to pass multiple tags the following error occures:

$ docker buildx build -t latest,test
error: "docker buildx build" requires exactly 1 argument.

It seems that currently it is only possible to pass multiple -t arguments for each tag, even though the docs state otherwise.

Can you please explain this behaviour?

[crazy-max]

@dudicoco

$ docker buildx build -t latest,test

You need to specify the context and also stringArray stores values as multiple flags compared to a stringSlice which takes comma-separated values:

$ docker buildx build -t latest -t test .

[jonstelly]

That PR might help clarify the difference?

[dudicoco]

Thanks @crazy-max, the context was missed during copy paste.

So i've encountered another issue with passing tags to the bake command when working with a docker-compose.yaml file.
Since the compose file does not allow to specify multiple tags per service, how can we specify multiple tags without using a docker-bake.json/hcl file?
Passing the tags via flags is not a good option as each target might use a different docker repository, for example:

services:
  app1:
    image: ${DOCKER_REGISTRY:-default}/app1:${TAG:-latest}
    build: app1/
  app2:
    image: ${DOCKER_REGISTRY:-default}/app2:${TAG:-latest}
    build: app2/