Running docker build from inside of dagger

[icy mural]

I have the following golang function which tries to build a docker image from inside of dagger, but I get this error:

func build_docker_image(ctx context.Context, client *dagger.Client) {
    // get reference to source code directory
    source := client.Host().Directory(".", dagger.HostDirectoryOpts{
        Exclude: []string{"ci", "build"},
    })

    app := client.Container().
        From("docker:25-dind").
        WithMountedDirectory("/src", source).
        WithWorkdir("/src")

    build, build_err := app.WithExec([]string{"docker", "build", "-t", "hexchess-server", "."}).Stdout(ctx)
    if build_err != nil {
        panic(build_err)
    }
    fmt.Println(build)

        // Tag and publish the build
}

[tame hearth]

This only runs the docker client inside a container. Are you trying to connect to an external docker engine? Do you specifically need to use a docker engine?

The simplest way to build an image from dockerfile is to call the builtin Directory.dockerBuild() function. It's fully compatible and doesn't require the docker cli or engine.

[icy mural]

Aaah, that would 100% solve my problem sorry haha

[tame hearth]

func build_docker_image(ctx context.Context, client *dagger.Client) {
    // get reference to source code directory
    source := client.Host().Directory(".", dagger.HostDirectoryOpts{
        Exclude: []string{"ci", "build"},
    })
    ctr := source.DockerBuild()
    ref, err := ctr.Publish(ctx, "myregistry/myimage:mytag")
}

[tame hearth]

Happy to help! That's why we're here 🙂

[icy mural]

Sorry, just to follow up here - I'm trying to find the equivalent of this command in dagger. Is that the https://github.com/dagger/dagger-go-sdk/blob/v0.10.1/dagger.gen.go#L1425 withRegistryAuth method?

My keytype is _json_key

[tame hearth]

Yes it's the withRegistryAuth method 👍

I think as a special case, Dagger will detect and use your local docker config

withRegistryAuth to be safe though

[icy mural]

Ok I got everything working and publishing. Last question here sorry - how do I tag the newly built docker container? What's the equivalent of docker tag ?
Everything I'm publishing to GCR is tagged w/ latest which I'd like to customize

[tame hearth]

You can pass the tag at publish . there is no local tag unlike docker engine.

[icy mural]

Is it meant to be passed in the name like ${url}:${tag} or is it part of the PublishOpts? It's not super clear where it's supposed to go sorry