An Easier Way to Create Tiny Golang Docker Images
Overview
Atlassian just posted a blog post about creating Static Go binaries with Docker on OSX which shows how to make a tiny little Docker image (~6MB total) with your Go program inside. When I read it, I thought “this is cool… but way too complicated”. I’ve been using Docker a lot lately and knew there had to be an easier way. Here is that way.
So we have our little Go program, this one is a simple web server using Gorilla mux for routing:
Now let’s get down to business.
Table of Contents
Related Reading: Docker inc isn't dead
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Vendor Dependencies
The first thing we want to do is vendor our dependencies. We’re going to use godep here:
go get github.com/gorilla/mux godep save -r
Build Static Binary
Now we build a static binary for our program. Yes, this looks scary, but just copy and paste it and you’re golden:
docker run --rm -it -v "$GOPATH":/gopath -v "$(pwd)":/app -e "GOPATH=/gopath" -w /app golang:1.4.2 sh -c 'CGO_ENABLED=0 go build -a --installsuffix cgo --ldflags="-s" -o hello'
You’ll end up with a binary called `hello`.
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Build Tiny Docker Image
Now we embed that `hello` binary in the smallest Docker image possible. The Dockerfile looks like this:
Now that we have the Dockerfile, just run:
docker build -t treeder/go-hello-http .
That will build an image named `treeder/go-hello-http` and it should only be about~4MB!!
Run/Test It
Now run it:
docker run --rm -it -p 8080:8080 treeder/go-hello-http
Surf to: http://localhost:8080/ . Boom.
That’s it. You now have a super simple, super tiny Docker image containing your Go program. If you want to share it with people, push it up to Docker hub and tell people to `docker run your/image`.
All the source code and everything can be found here:https://github.com/treeder/tiny-golang-docker
If you want to read more about developing your apps with Docker, check out my previous post.
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do you have the go 1.5 params for static linking?
I think I need a few more details, because that scary statement just errors for me and I really don’t even know where to start to fix it.
docker: Error response from daemon: invalid volume spec “:/gopath”: invalid volume specification: ‘:/gopath’.