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Version: 1.10.0

Custom a custom Builder image

The default builder image used by Epinio (paketobuildpacks/builder:full) may not work for every application. This could happen if a non-supported programming language is used, or when the application needs to be staged in a very specific way. This page explains how a custom builder image can be built that includes one or more buildpacks. We don't explain how to create a custom buildpack in this guide (upstream docs or with packit).


If you are familiar with the pack cli you know that it's possible to add a buildpack to a project using project.toml:

id = "sample"
version = "0.1"


id = "paketo-community/python"
version = "0.4.2"

Pack can then build the image for the application by running pack build test/pip -B paketobuildpacks/builder:full.

However, since Epinio is not using pack but the lifecycle directly (link 1, link 2), using project.toml is not possible:

Solution: Using a Custom Builder

We can create a custom builder that supports Python and tell Epinio to use that for staging.

git clone

patch -p1 <<EOF
diff --git a/builder.toml b/builder.toml
index f3a35fd..b228671 100644
--- a/builder.toml
+++ b/builder.toml
@@ -32,6 +32,10 @@ description = "Ubuntu bionic base image with buildpacks for Java, .NET Core, Nod
uri = "docker://"
version = "0.5.0"

+ uri = "docker://"
+ version = "0.4.2"
uri = "docker://"
version = "4.2.2"
@@ -97,6 +101,12 @@ description = "Ubuntu bionic base image with buildpacks for Java, .NET Core, Nod
id = "paketo-buildpacks/java"
version = "5.9.1"

+ [[]]
+ id = "paketo-community/python"
+ version = "0.4.2"


pack builder create myorg/epicustombuilder --config builder.toml

Make the image epicustombuilder:local available to your cluster by pushing it to a container registry. You can then push your application to Epinio and use your image with the --builder-image flag:

epinio push -n myapp -p app_directory --builder-image myorg/epicustombuilder:latest

More examples

You can find a more complete example on how to build and deploy a custom builder here: