My goal was compiling Caddy for my old Raspberry Pi 1 Model B. Caddy only provides an ARMv7 binary which isn’t compatible to the original Pis ARMv6. My Raspi is running on Hypriot, the Docker distribution for the Pi, therefore I wanted Caddy to run in a container as well. I chose my own Alpine Linux base image as its foundation.

As Caddy is written in Go, compiling it from source should be very easy:

1. go get github.com/mholt/caddy/caddy
2. cd into your website’s directory
3. Run caddy (assuming $GOPATH/bin is in your $PATH)

While trying to get Go running in my Alpine container I encountered a small problem.
Go officialy provides an ARMv6 binary package, which is able to natively run on the Pi. But when trying to run this package in my Alpine container, a rather nondescriptive error blocked me:

/bin/sh: go: not found

I admit I needed longer than expected to solve this problem. After straceing, debugging and a lot of Internet research without result, using a simple file gave me the deciding hint:

/go # file $(which go)
/usr/local/go/bin/go: ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux-armhf.so.3, not stripped

Go is looking for /lib/ld-linux-armhf.so.3 which isn’t available on a minimal Alpine Linux installation. Running apk add libc6-compat finally solved this problem.

Now compiling Caddy was easy:

1. Set the GOPATH. For me, that dir is simply /go: export GOPATH=/go
2. Run the previously mentioned go get github.com/mholt/caddy/caddy. This took ~15 minutes on my Raspberry Pi 1 Model B.

If you want to add additional plugins to caddy, you need to add their sources to the caddy/caddymain/run.go file and run go install github.com/mholt/caddy/caddy afterwards. Adding the realip plugin would look like that:

[...]
// plug in the HTTP server type
_ "github.com/mholt/caddy/caddyhttp"

"github.com/mholt/caddy/caddytls"
// This is where other plugins get plugged in (imported)
_ "github.com/captncraig/caddy-realip"

[...]

I’ve created a couple of Dockerfiles and scripts in my dockerfiles-arm repo which should ease this process for others. Furthermore I’ve created a couple of containers for the impatient (Go, Caddy), although I’d recommend the Dockerfiles.

For more info about configuration of Caddy, see the documentation and the Github source. I’ll try to distribute an automatically compiled binary of Caddy for ARMv6, but I can’t promise anything.