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* update docs: fix broken links, align with README * update google/ko references that can be updated
65 lines
2.1 KiB
Markdown
65 lines
2.1 KiB
Markdown
# Migrating from Dockerfile
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If your `Dockerfile` looks like either of the examples in the [official tutorial for writing a Dockerfile to containerize a Go application](https://docs.docker.com/language/golang/build-images/), you can easily migrate to use `ko` instead.
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Let's review the best practice multi-stage Dockerfile in that tutorial first:
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```plaintext
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# syntax=docker/dockerfile:1
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##
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## Build
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##
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FROM golang:1.16-buster AS build
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WORKDIR /app
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COPY go.mod ./
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COPY go.sum ./
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RUN go mod download
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COPY *.go ./
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RUN go build -o /docker-gs-ping
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##
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## Deploy
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##
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FROM gcr.io/distroless/base-debian10
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WORKDIR /
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COPY --from=build /docker-gs-ping /docker-gs-ping
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EXPOSE 8080
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USER nonroot:nonroot
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ENTRYPOINT ["/docker-gs-ping"]
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```
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This `Dockerfile`:
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1. pulls the `golang:1.16` image
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1. `COPY`s your local source into the container environment (`COPY`ing `go.mod` and `go.sum` first and running `go mod download`, to cache dependencies in the container environment)
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1. `RUN`s `go build` on your source, inside the container, to produce an executable
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1. `COPY`s the executable built in the previous step into a new image, on top of a minimal [distroless](https://github.com/GoogleContainerTools/distroless) base image.
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The result is a Go application built on a minimal base image, with an optimally cached build sequence.
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After running `docker build` on this `Dockerfile`, don't forget to push that image to the registry so you can deploy it.
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---
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## Migrating to `ko`
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If your Go source is laid out as described in the tutorial, and you've [installed](../../install) and [set up your environment](../../get-started), you can simply run `ko build ./` to build and push the container image to your registry.
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You're done. You can delete your `Dockerfile` and uninstall `docker`.
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`ko` takes advantage of your local [Go build cache](../../features/build-cache) without needing to be told to, and it sets the `ENTRYPOINT` and uses a nonroot distroless base image by default.
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To build a multi-arch image, simply add `--platform=all`.
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Compare this to the [equivalent Docker instructions](https://docs.docker.com/desktop/multi-arch/).
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