paketo-buildpacks/bellsoft-liberica : using from the local dir

[ildar]

I'm (very) new to buildpacks and having a problem with using a custom buildpack from a local directory.

default buildpack

1st, I can use the default buildpack for building and running a Java application (sample app downloaded from https://start.spring.io/) One little log for it: bp1.log

buildpack from a local directory

Unfortunately I can't get (the same?) bellsoft-liberica work for the same scenario from a local folder. I try it like this (after running scripts/build.sh):

pack -v build demo-app --path . --buildpack ../buildpacks/bellsoft-liberica -e BP_JVM_VERSION=17

and get this error:

[detector] target distro name/version labels not found, reading /etc/os-release file
[detector] ======== Error: paketo-buildpacks/bellsoft-liberica@{{.version}} ========
[detector] fork/exec /cnb/buildpacks/paketo-buildpacks_bellsoft-liberica/{{.version}}/bin/detect: no such file or directory
[detector] ======== Results ========
[detector] err:  paketo-buildpacks/bellsoft-liberica@{{.version}}
[detector] Timer: Detector ran for 5.097592ms and ended at 2025-01-27T13:18:54Z
[detector] ERROR: No buildpack groups passed detection.
[detector] ERROR: failed to detect: buildpack(s) failed with err
ERROR: failed to build: executing lifecycle: failed with status code: 21

The full log bp2.log

playing with detect and build

1. Since it cannot find the detect script, I put the binaries produced by scripts/build.sh into the buildpacks/bellsoft-liberica/bin. Detect fails again.
2. If I replace detect by a stub (with exit 0) then pack build finishes without gradle build
3. stubbing build doesn't help either.

I suspect there is a little thing I simply overlook. Please drop me a hint. Thanks in advance.

[dmikusa]

The trick with Paketo buildpacks is that we write them in Go, so they need compiled before you can run them as a buildpack. We have a tool for doing that, libpak-tools. You can use libpak-tools package compile if you want to build the buildpack into a local directory & point to that directory with pack build -b.

You can also run libpak-tools package bundle which does the same thing but then produces an image in your Docker daemon with the buildpack. You can then pack build -b and set the image like docker.io/paketo-buildpacks/bellsoft-liberica and it'll pull the local image.

Either works.

As an aside, you can do this without libpak-tools, but the tool automates the process so we recommend everyone use the tool.

One last note...

pack -v build demo-app --path . --buildpack ../buildpacks/bellsoft-liberica -e BP_JVM_VERSION=17

When you use the -b or --buildpack argument, you MUST specify the entire set of buildpacks to use. By setting --buildpack ../buildpacks/bellsoft-liberica you're telling pack to use one and only one buildpack, which isn't going to work.

The easiest way to figure out the full set of buildpacks is to pack build without -b and see what detects. Then you can pack build -b .. -b .. -b .. and add all of the buildpacks from the detect output, overriding the ones you want to customize.

Hope that helps!