Creating debs and rpms with Go

I’ve been working on GoReleaser for more than a year now, and one of the things that was bothering me the most was fpm.

Not that fpm is bad or anything like that, is just that it can be unstable: it uses the system tar (GNU tar is different from BSD tar) and its written in ruby, which requires the user to deal with ruby versions, gems and all that.

I wanted something simpler, predictable and that could be used as a lib and as a binary. Couldn’t find anything like that, so I went ahead and tried to implement it myself in Go, using the minimum external dependencies.

Thus, nfpm was born.

NFPM stands for Not FPM. It’s not a very good name, and I know I suck at naming things.

Anyway, its usage as a lib is kind of simple and it is easy to extend:

package main

import (
	"io/ioutil"
	"log"

	"github.com/goreleaser/nfpm"
	_ "github.com/goreleaser/nfpm/deb"
)

func main() {
	pkg, err := nfpm.Get("deb")
	if err != nil {
		log.Fatalln(err)
	}
	if err := pkg.Package(nfpm.Info{
		Name:        "my-pkg",
		Arch:        "amd64",
		Platform:    "linux",
		Version:     "1.2.3",
		Section:     "",
		Priority:    "",
		Replaces:    nil,
		Provides:    nil,
		Depends:     nil,
		Recommends:  nil,
		Suggests:    nil,
		Conflicts:   nil,
		Maintainer:  "",
		Description: "",
		Vendor:      "",
		Homepage:    "",
		License:     "",
		Bindir:      "",
		Files:       map[string]string{
			// "./local/path": "/path/inside/pkg",
		},
		ConfigFiles: map[string]string{
			// same thing as files, but they are treated different by deb/rpm themselves
		},
	}, ioutil.Discard); err != nil {
		log.Fatalln(err)
	}
}

As you can see, there are quite a few options, not all of them are required, though.

NFPM can also be installed as a binary, which you can use to generate packages for your software, or, you can use it through GoReleaser, which will automate the entire release process for you.

Design decisions

The idea of the Register function and blank imports is based on the database/sql package. I’m not sure this was the best idea, and I may change this in the future, but it does allow to simply add more packagers and as well to import only the ones you want.

Unfortunately, I was unable to generate rpm packages without rpmbuild, so there is this one dependency if you want rpm packages.

On the bright side, generating debs was almost too easy: a couple of tar.gz and text files inside an ar file and that was it, working like a charm. All done natively with Go code.

Future ahead

Maybe eventually we could add more formats - I’m not sure. Generating deb and rpm packages cover most of the cases I believe, and Snapcraft packages are already supported by GoReleaser in a different pipe.

We will need a full suite of acceptance tests at some point - PRs welcome!

On the GoReleaser side of things, fpm removal is about to happen, and it will automagically default to nfpm.