[[build-image]]
= Packaging OCI Images
The plugin can create an https://github.com/opencontainers/image-spec[OCI image] from a jar or war file using https://buildpacks.io[Cloud Native Buildpacks] (CNB).
Images can be built using the `bootBuildImage` task.

NOTE: For security reasons, images build and run as non-root users.
See the {buildpacks-reference}/reference/spec/platform-api/#users[CNB specification] for more details.

The task is automatically created when the `java` or `war` plugin is applied and is an instance of {boot-build-image-javadoc}[`BootBuildImage`].



[[build-image.docker-daemon]]
== Docker Daemon
The `bootBuildImage` task requires access to a Docker daemon.
By default, it will communicate with a Docker daemon over a local connection.
This works with https://docs.docker.com/install/[Docker Engine] on all supported platforms without configuration.

Environment variables can be set to configure the `bootBuildImage` task to use an alternative local or remote connection.
The following table shows the environment variables and their values:

|===
| Environment variable | Description

| DOCKER_HOST
| URL containing the host and port for the Docker daemon - for example `tcp://192.168.99.100:2376`

| DOCKER_TLS_VERIFY
| Enable secure HTTPS protocol when set to `1` (optional)

| DOCKER_CERT_PATH
| Path to certificate and key files for HTTPS (required if `DOCKER_TLS_VERIFY=1`, ignored otherwise)
|===

Docker daemon connection information can also be provided using `docker` properties in the plugin configuration.
The following table summarizes the available properties:

|===
| Property | Description

| `host`
| URL containing the host and port for the Docker daemon - for example `tcp://192.168.99.100:2376`

| `tlsVerify`
| Enable secure HTTPS protocol when set to `true` (optional)

| `certPath`
| Path to certificate and key files for HTTPS (required if `tlsVerify` is `true`, ignored otherwise)

| `bindHostToBuilder`
| When `true`, the value of the `host` property will be provided to the container that is created for the CNB builder (optional)
|===

For more details, see also <<build-image.examples.docker,examples>>.



[[build-image.docker-registry]]
== Docker Registry
If the Docker images specified by the `builder` or `runImage` properties are stored in a private Docker image registry that requires authentication, the authentication credentials can be provided using `docker.builderRegistry` properties.

If the generated Docker image is to be published to a Docker image registry, the authentication credentials can be provided using `docker.publishRegistry` properties.

Properties are provided for user authentication or identity token authentication.
Consult the documentation for the Docker registry being used to store images for further information on supported authentication methods.

The following table summarizes the available properties for `docker.builderRegistry` and `docker.publishRegistry`:

|===
| Property | Description

| `username`
| Username for the Docker image registry user. Required for user authentication.

| `password`
| Password for the Docker image registry user. Required for user authentication.

| `url`
| Address of the Docker image registry. Optional for user authentication.

| `email`
| E-mail address for the Docker image registry user. Optional for user authentication.

| `token`
| Identity token for the Docker image registry user. Required for token authentication.
|===

For more details, see also <<build-image.examples.docker,examples>>.



[[build-image.customization]]
== Image Customizations
The plugin invokes a {buildpacks-reference}/concepts/components/builder/[builder] to orchestrate the generation of an image.
The builder includes multiple {buildpacks-reference}/concepts/components/buildpack[buildpacks] that can inspect the application to influence the generated image.
By default, the plugin chooses a builder image.
The name of the generated image is deduced from project properties.

Task properties can be used to configure how the builder should operate on the project.
The following table summarizes the available properties and their default values:

|===
| Property | Command-line option | Description | Default value

| `builder`
| `--builder`
| Name of the Builder image to use.
| `paketobuildpacks/builder:base` or `paketobuildpacks/builder:tiny` when {nbt-gradle-plugin}[GraalVM Native Image plugin] is applied.

| `runImage`
| `--runImage`
| Name of the run image to use.
| No default value, indicating the run image specified in Builder metadata should be used.

| `imageName`
| `--imageName`
| {spring-boot-api}/buildpack/platform/docker/type/ImageReference.html#of-java.lang.String-[Image name] for the generated image.
| `docker.io/library/${project.name}:${project.version}`

| `pullPolicy`
| `--pullPolicy`
| {spring-boot-api}/buildpack/platform/build/PullPolicy.html[Policy] used to determine when to pull the builder and run images from the registry.
Acceptable values are `ALWAYS`, `NEVER`, and `IF_NOT_PRESENT`.
| `ALWAYS`

| `environment`
|
| Environment variables that should be passed to the builder.
| Empty or `['BP_NATIVE_IMAGE': 'true']` when {nbt-gradle-plugin}[GraalVM Native Image plugin] is applied.

| `buildpacks`
|
a|Buildpacks that the builder should use when building the image.
Only the specified buildpacks will be used, overriding the default buildpacks included in the builder.
Buildpack references must be in one of the following forms:

* Buildpack in the builder - `[urn:cnb:builder:]<buildpack ID>[@<version>]`
* Buildpack in a directory on the file system - `[file://]<path>`
* Buildpack in a gzipped tar (.tgz) file on the file system - `[file://]<path>/<file name>`
* Buildpack in an OCI image - `[docker://]<host>/<repo>[:<tag>][@<digest>]`
| None, indicating the builder should use the buildpacks included in it.

| `bindings`
|
a|https://docs.docker.com/storage/bind-mounts/[Volume bind mounts] that should be mounted to the builder container when building the image.
The bindings will be passed unparsed and unvalidated to Docker when creating the builder container.
Bindings must be in one of the following forms:

* `<host source path>:<container destination path>[:<options>]`
* `<host volume name>:<container destination path>[:<options>]`

Where `<options>` can contain:

* `ro` to mount the volume as read-only in the container
* `rw` to mount the volume as readable and writable in the container
* `volume-opt=key=value` to specify key-value pairs consisting of an option name and its value
|

| `network`
| `--network`
| The https://docs.docker.com/network/#network-drivers[network driver] the builder container will be configured to use.
The value supplied will be passed unvalidated to Docker when creating the builder container.
|

| `cleanCache`
| `--cleanCache`
| Whether to clean the cache before building.
| `false`

| `verboseLogging`
|
| Enables verbose logging of builder operations.
| `false`

| `publish`
| `--publishImage`
| Whether to publish the generated image to a Docker registry.
| `false`

| `tags`
|
| A list of one or more additional tags to apply to the generated image.
The values provided to the `tags` option should be full image references in the form of `[image name]:[tag]` or `[repository]/[image name]:[tag]`.
|

| `buildCache`
|
| A cache containing layers created by buildpacks and used by the image building process.
| A named volume in the Docker daemon, with a name derived from the image name.

| `launchCache`
|
| A cache containing layers created by buildpacks and used by the image launching process.
| A named volume in the Docker daemon, with a name derived from the image name.

| `createdDate`
| `--createdDate`
| A date that will be used to set the `Created` field in the generated image's metadata.
The value must be a string in the ISO 8601 instant format, or `now` to use the current date and time.
| A fixed date that enables https://buildpacks.io/docs/features/reproducibility/[build reproducibility].

| `applicationDirectory`
| `--applicationDirectory`
| The path to a directory that application contents will be uploaded to in the builder image.
Application contents will also be in this location in the generated image.
| `/workspace`

|===

NOTE: The plugin detects the target Java compatibility of the project using the JavaPlugin's `targetCompatibility` property.
When using the default Paketo builder and buildpacks, the plugin instructs the buildpacks to install the same Java version.
You can override this behaviour as shown in the <<build-image.examples.builder-configuration,builder configuration>> examples.



[[build-image.examples]]
== Examples



[[build-image.examples.custom-image-builder]]
=== Custom Image Builder and Run Image
If you need to customize the builder used to create the image or the run image used to launch the built image, configure the task as shown in the following example:

[source,groovy,indent=0,subs="verbatim,attributes",role="primary"]
.Groovy
----
include::../gradle/packaging/boot-build-image-builder.gradle[tags=builder]
----

[source,kotlin,indent=0,subs="verbatim,attributes",role="secondary"]
.Kotlin
----
include::../gradle/packaging/boot-build-image-builder.gradle.kts[tags=builder]
----

This configuration will use a builder image with the name `mine/java-cnb-builder` and the tag `latest`, and the run image named `mine/java-cnb-run` and the tag `latest`.

The builder and run image can be specified on the command line as well, as shown in this example:

[indent=0]
----
	$ gradle bootBuildImage --builder=mine/java-cnb-builder --runImage=mine/java-cnb-run
----



[[build-image.examples.builder-configuration]]
=== Builder Configuration
If the builder exposes configuration options, those can be set using the `environment` property.

The following is an example of {paketo-java-reference}/#configuring-the-jvm-version[configuring the JVM version] used by the Paketo Java buildpacks at build time:

[source,groovy,indent=0,subs="verbatim,attributes",role="primary"]
.Groovy
----
include::../gradle/packaging/boot-build-image-env.gradle[tags=env]
----

[source,kotlin,indent=0,subs="verbatim,attributes",role="secondary"]
.Kotlin
----
include::../gradle/packaging/boot-build-image-env.gradle.kts[tags=env]
----

If there is a network proxy between the Docker daemon the builder runs in and network locations that buildpacks download artifacts from, you will need to configure the builder to use the proxy.
When using the Paketo builder, this can be accomplished by setting the `HTTPS_PROXY` and/or `HTTP_PROXY` environment variables as show in the following example:

[source,groovy,indent=0,subs="verbatim,attributes",role="primary"]
.Groovy
----
include::../gradle/packaging/boot-build-image-env-proxy.gradle[tags=env]
----

[source,kotlin,indent=0,subs="verbatim,attributes",role="secondary"]
.Kotlin
----
include::../gradle/packaging/boot-build-image-env-proxy.gradle.kts[tags=env]
----



[[build-image.examples.runtime-jvm-configuration]]
=== Runtime JVM Configuration
Paketo Java buildpacks {paketo-java-reference}/#runtime-jvm-configuration[configure the JVM runtime environment] by setting the `JAVA_TOOL_OPTIONS` environment variable.
The buildpack-provided `JAVA_TOOL_OPTIONS` value can be modified to customize JVM runtime behavior when the application image is launched in a container.

Environment variable modifications that should be stored in the image and applied to every deployment can be set as described in the {paketo-reference}/buildpacks/configuration/#environment-variables[Paketo documentation] and shown in the following example:

[source,groovy,indent=0,subs="verbatim,attributes",role="primary"]
.Groovy
----
include::../gradle/packaging/boot-build-image-env-runtime.gradle[tags=env-runtime]
----

[source,kotlin,indent=0,subs="verbatim,attributes",role="secondary"]
.Kotlin
----
include::../gradle/packaging/boot-build-image-env-runtime.gradle.kts[tags=env-runtime]
----



[[build-image.examples.custom-image-name]]
=== Custom Image Name
By default, the image name is inferred from the `name` and the `version` of the project, something like `docker.io/library/${project.name}:${project.version}`.
You can take control over the name by setting task properties, as shown in the following example:

[source,groovy,indent=0,subs="verbatim,attributes",role="primary"]
.Groovy
----
include::../gradle/packaging/boot-build-image-name.gradle[tags=image-name]
----

[source,kotlin,indent=0,subs="verbatim,attributes",role="secondary"]
.Kotlin
----
include::../gradle/packaging/boot-build-image-name.gradle.kts[tags=image-name]
----

Note that this configuration does not provide an explicit tag so `latest` is used.
It is possible to specify a tag as well, either using `${project.version}`, any property available in the build or a hardcoded version.

The image name can be specified on the command line as well, as shown in this example:

[indent=0]
----
	$ gradle bootBuildImage --imageName=example.com/library/my-app:v1
----



[[build-image.examples.buildpacks]]
=== Buildpacks
By default, the builder will use buildpacks included in the builder image and apply them in a pre-defined order.
An alternative set of buildpacks can be provided to apply buildpacks that are not included in the builder, or to change the order of included buildpacks.
When one or more buildpacks are provided, only the specified buildpacks will be applied.

The following example instructs the builder to use a custom buildpack packaged in a `.tgz` file, followed by a buildpack included in the builder.

[source,groovy,indent=0,subs="verbatim,attributes",role="primary"]
.Groovy
----
include::../gradle/packaging/boot-build-image-buildpacks.gradle[tags=buildpacks]
----

[source,kotlin,indent=0,subs="verbatim,attributes",role="secondary"]
.Kotlin
----
include::../gradle/packaging/boot-build-image-buildpacks.gradle.kts[tags=buildpacks]
----

Buildpacks can be specified in any of the forms shown below.

A buildpack located in a CNB Builder (version may be omitted if there is only one buildpack in the builder matching the `buildpack-id`):

* `urn:cnb:builder:buildpack-id`
* `urn:cnb:builder:buildpack-id@0.0.1`
* `buildpack-id`
* `buildpack-id@0.0.1`

A path to a directory containing buildpack content (not supported on Windows):

* `\file:///path/to/buildpack/`
* `/path/to/buildpack/`

A path to a gzipped tar file containing buildpack content:

* `\file:///path/to/buildpack.tgz`
* `/path/to/buildpack.tgz`

An OCI image containing a https://buildpacks.io/docs/buildpack-author-guide/package-a-buildpack/[packaged buildpack]:

* `docker://example/buildpack`
* `docker:///example/buildpack:latest`
* `docker:///example/buildpack@sha256:45b23dee08...`
* `example/buildpack`
* `example/buildpack:latest`
* `example/buildpack@sha256:45b23dee08...`



[[build-image.examples.publish]]
=== Image Publishing
The generated image can be published to a Docker registry by enabling a `publish` option.

If the Docker registry requires authentication, the credentials can be configured using `docker.publishRegistry` properties.
If the Docker registry does not require authentication, the `docker.publishRegistry` configuration can be omitted.

NOTE: The registry that the image will be published to is determined by the registry part of the image name (`docker.example.com` in these examples).
If `docker.publishRegistry` credentials are configured and include a `url` property, this value is passed to the registry but is not used to determine the publishing registry location.

[source,groovy,indent=0,subs="verbatim,attributes",role="primary"]
.Groovy
----
include::../gradle/packaging/boot-build-image-publish.gradle[tags=publish]
----

[source,kotlin,indent=0,subs="verbatim,attributes",role="secondary"]
.Kotlin
----
include::../gradle/packaging/boot-build-image-publish.gradle.kts[tags=publish]
----

The publish option can be specified on the command line as well, as shown in this example:

[indent=0]
----
	$ gradle bootBuildImage --imageName=docker.example.com/library/my-app:v1 --publishImage
----

[[build-image.examples.caches]]
=== Builder Cache Configuration

The CNB builder caches layers that are used when building and launching an image.
By default, these caches are stored as named volumes in the Docker daemon with names that are derived from the full name of the target image.
If the image name changes frequently, for example when the project version is used as a tag in the image name, then the caches can be invalidated frequently.

The cache volumes can be configured to use alternative names to give more control over cache lifecycle as shown in the following example:

[source,groovy,indent=0,subs="verbatim,attributes",role="primary"]
.Groovy
----
include::../gradle/packaging/boot-build-image-caches.gradle[tags=caches]
----

[source,kotlin,indent=0,subs="verbatim,attributes",role="secondary"]
.Kotlin
----
include::../gradle/packaging/boot-build-image-caches.gradle.kts[tags=caches]
----

[[build-image.examples.docker]]
=== Docker Configuration

[[build-image.examples.docker.minikube]]
==== Docker Configuration for minikube

The plugin can communicate with the https://minikube.sigs.k8s.io/docs/tasks/docker_daemon/[Docker daemon provided by minikube] instead of the default local connection.

On Linux and macOS, environment variables can be set using the command `eval $(minikube docker-env)` after minikube has been started.

The plugin can also be configured to use the minikube daemon by providing connection details similar to those shown in the following example:

[source,groovy,indent=0,subs="verbatim,attributes",role="primary"]
.Groovy
----
include::../gradle/packaging/boot-build-image-docker-host.gradle[tags=docker-host]
----

[source,kotlin,indent=0,subs="verbatim,attributes",role="secondary"]
.Kotlin
----
include::../gradle/packaging/boot-build-image-docker-host.gradle.kts[tags=docker-host]
----

[[build-image.examples.docker.podman]]
==== Docker Configuration for podman

The plugin can communicate with a https://podman.io/[podman container engine].

The plugin can be configured to use podman local connection by providing connection details similar to those shown in the following example:

[source,groovy,indent=0,subs="verbatim,attributes",role="primary"]
.Groovy
----
include::../gradle/packaging/boot-build-image-docker-host-podman.gradle[tags=docker-host]
----

[source,kotlin,indent=0,subs="verbatim,attributes",role="secondary"]
.Kotlin
----
include::../gradle/packaging/boot-build-image-docker-host-podman.gradle.kts[tags=docker-host]
----

TIP: With the `podman` CLI installed, the command `podman info --format='{{.Host.RemoteSocket.Path}}'` can be used to get the value for the `docker.host` configuration property shown in this example.

[[build-image.examples.docker.auth]]
==== Docker Configuration for Authentication

If the builder or run image are stored in a private Docker registry that supports user authentication, authentication details can be provided using `docker.builderRegistry` properties as shown in the following example:

[source,groovy,indent=0,subs="verbatim,attributes",role="primary"]
.Groovy
----
include::../gradle/packaging/boot-build-image-docker-auth-user.gradle[tags=docker-auth-user]
----

[source,kotlin,indent=0,subs="verbatim,attributes",role="secondary"]
.Kotlin
----
include::../gradle/packaging/boot-build-image-docker-auth-user.gradle.kts[tags=docker-auth-user]
----

If the builder or run image is stored in a private Docker registry that supports token authentication, the token value can be provided using `docker.builderRegistry` as shown in the following example:

[source,groovy,indent=0,subs="verbatim,attributes",role="primary"]
.Groovy
----
include::../gradle/packaging/boot-build-image-docker-auth-token.gradle[tags=docker-auth-token]
----

[source,kotlin,indent=0,subs="verbatim,attributes",role="secondary"]
.Kotlin
----
include::../gradle/packaging/boot-build-image-docker-auth-token.gradle.kts[tags=docker-auth-token]
----
