Cross compiling Go applications

April 8 - 2017
meta Go

I often write blog posts on different computers. Sometimes I write on my Macbook (which is where I run a local Hugo server to test things out), other times I SSH into my Raspberry Pi and write there until I am on my Macbook again. While writing my Why I learned Python blog post I asked some friends for feedback, however, I did not want to push an unfinished post to Github Pages, so I decided to serve my Hugo blog from my Raspberry Pi. I soon realized that I would have to install Hugo from source which could mean trouble…

Version mess

I bought a Raspberry Pi in late 2012, so I have one of the original Raspberry Pi Model B which are… well… pretty underpowered. This is usually not a problem as I tend to run services which do not need much resources. In it, I am running a headless setup of Debian 8, which as we all know probably has some outdated packages, but this tends not to be a problem, until now.

My blog is designed to work with Hugo 0.18+, however, it is not available in the Debian repositories (well, no version is available actually). This should be a non-issue, as all it takes is a go get to pull and compile the latest version. Little did I know that the latest Go version available for Debian 8 seems to be 1.3 which is not new enough for building Hugo. I could always compile a new Go version, but there’s a big gotcha, with Go 1.5 the compiler and runtime were rewritten in Go, meaning that Go 1.4+ is needed for building it. This means that in order to install Hugo 0.18 I would have to compile Go 1.4 first and then compile Go 1.8. All of that on a Raspberry Pi? No thank you.

Cross compilation to the rescue

I figured that there must be a simpler way of getting Hugo 0.18 on there, so I started doing some research to see whether it was possible (and how hard it would be) to compile a Hugo binary on another architecture (x86_64 in this case). I soon came across this blog post that explained how to go about cross compiling code. I decided to try this on my Macbook, as it was what I was using. The instructions seemed a bit too simple though, I was sure I was going to run into other issues. Cross compiling could not be this easy, could it? Well yes, it was. I was pleasantly surprised at how smooth it all went and how quick it was. All it took was running:

env GOOS=linux GOARCH=arm GOARM=6 go build -v

I then scp-ed my freshly built binary and BAM! It worked flawlessly!

Feeling dumb as bricks

It turns out it did not have to go through all this trouble to get Hugo on Brinstar (thats what my Pi is called), as the Hugo releases page has binaries for ARM (though I did not test if they worked or not). Not only that, the Go downloads page provides ARMv6l binaries which for sure work on my model, I could have just downloaded that!

Judge Judy is not pleased

The moral of the story is: always look for pre-built binaries. All jokes aside, I was surprised at how uncomplicated cross compiling a Go binary was, which depending on what type of software you’re building could be a very big plus.