[id="understanding-odo"]
= Understanding `odo`
include::modules/developer-cli-odo-attributes.adoc[]
include::modules/common-attributes.adoc[]
:context: understanding-odo
toc::[]

`{odo-title}` is a CLI tool for creating applications on {product-title} and Kubernetes. With `{odo-title}`, you can write, build, and debug applications on a cluster without the need to administer the cluster itself.
Creating deployment configurations, build configurations, service routes and other {product-title} or Kubernetes elements are all automated by `{odo-title}`.

Existing tools such as xref:../../cli_reference/openshift_cli/getting-started-cli.adoc#cli-about-cli_cli-developer-commands[`oc`] are operations-focused and require a deep understanding of Kubernetes and {product-title} concepts. `{odo-title}` abstracts away complex Kubernetes and {product-title} concepts allowing developers to focus on what is most important to them: code.

[id="odo-key-features"]
== Key features

`{odo-title}` is designed to be simple and concise with the following key features:

* Simple syntax and design centered around concepts familiar to developers, such as projects, applications, and components.
* Completely client based. No additional server other than {product-title} is required for deployment.
* Official support for Node.js and Java components.
* Partial compatibility with languages and frameworks such as Ruby, Perl, PHP, and Python.
* Detects changes to local code and deploys it to the cluster automatically, giving instant feedback to validate changes in real time.
* Lists all the available components and services from the cluster.

== Core concepts

Project::
A project is your source code, tests, and libraries organized in a separate single unit.
Application::
An application is a program designed for end users. An application consists of multiple microservices or components that work individually to build the entire application.
Examples of applications: a video game, a media player, a web browser.
Component::
A component is a set of Kubernetes resources which host code or data. Each component can be run and deployed separately.
Examples of components: Node.js, Perl, PHP, Python, Ruby.
Service::
A service is software that your component links to or depends on.
Examples of services: MariaDB, Jenkins, MySQL.
In `{odo-title}`, services are provisioned from the OpenShift Service Catalog and must be enabled within your cluster.

[id="odo-supported-languages-and-images"]
=== Officially supported languages and corresponding container images

.Supported languages, container images, package managers, and platforms
[options="header"]
|===
|Language |Container image |Package manager |Platform
|*Node.js*
|https://access.redhat.com/containers/#/registry.access.redhat.com/rhscl/nodejs-10-rhel7[rhscl/nodejs-10-rhel7]
|NPM
|amd64, s390x, ppc64le

|
|https://access.redhat.com/containers/#/registry.access.redhat.com/rhscl/nodejs-12-rhel7[rhscl/nodejs-12-rhel7]
|NPM
|amd64, s390x, ppc64le

|*Java*
|https://access.redhat.com/containers/#/registry.access.redhat.com/redhat-openjdk-18/openjdk18-openshift[redhat-openjdk-18/openjdk18-openshift]
|Maven, Gradle
|amd64, s390x, ppc64le

|
|https://access.redhat.com/containers/#/registry.access.redhat.com/openjdk/openjdk-11-rhel8[openjdk/openjdk-11-rhel8]
|Maven, Gradle
|amd64, s390x, ppc64le

|
|https://access.redhat.com/containers/#/registry.access.redhat.com/openjdk/openjdk-11-rhel7[openjdk/openjdk-11-rhel7]
|Maven, Gradle
|amd64, s390x, ppc64le
|===

[id="odo-listing-available-images"]
==== Listing available container images

[NOTE]
====
The list of available container images is sourced from the cluster's internal container registry and external registries associated with the cluster.
====

To list the available components and associated container images for your cluster:

. Log in to the cluster with `{odo-title}`:
+
[source,terminal]
----
$ odo login -u developer -p developer
----

. List the available `{odo-title}` supported and unsupported components and corresponding container images:
+
[source,terminal]
----
$ odo catalog list components
----
+
.Example output
[source,terminal]
----
Odo Devfile Components:
NAME                 DESCRIPTION                            REGISTRY
java-maven           Upstream Maven and OpenJDK 11          DefaultDevfileRegistry
java-openliberty     Open Liberty microservice in Java      DefaultDevfileRegistry
java-quarkus         Upstream Quarkus with Java+GraalVM     DefaultDevfileRegistry
java-springboot      Spring Boot® using Java                DefaultDevfileRegistry
nodejs               Stack with NodeJS 12                   DefaultDevfileRegistry

Odo OpenShift Components:
NAME        PROJECT       TAGS                                                                           SUPPORTED
java        openshift     11,8,latest                                                                    YES
dotnet      openshift     2.1,3.1,latest                                                                 NO
golang      openshift     1.13.4-ubi7,1.13.4-ubi8,latest                                                 NO
httpd       openshift     2.4-el7,2.4-el8,latest                                                         NO
nginx       openshift     1.14-el7,1.14-el8,1.16-el7,1.16-el8,latest                                     NO
nodejs      openshift     10-ubi7,10-ubi8,12-ubi7,12-ubi8,latest                                         NO
perl        openshift     5.26-el7,5.26-ubi8,5.30-el7,latest                                             NO
php         openshift     7.2-ubi7,7.2-ubi8,7.3-ubi7,7.3-ubi8,latest                                     NO
python      openshift     2.7-ubi7,2.7-ubi8,3.6-ubi7,3.6-ubi8,3.8-ubi7,3.8-ubi8,latest                   NO
ruby        openshift     2.5-ubi7,2.5-ubi8,2.6-ubi7,2.6-ubi8,2.7-ubi7,latest                            NO
wildfly     openshift     10.0,10.1,11.0,12.0,13.0,14.0,15.0,16.0,17.0,18.0,19.0,20.0,8.1,9.0,latest     NO
----
+
The `TAGS` column represents the available image versions, for example, `10` represents the `rhoar-nodejs/nodejs-10` container image.
To learn more about CLI commands, go to xref:../../cli_reference/developer_cli_odo/odo-cli-reference.adoc#basic-odo-cli-commands_odo-cli-reference[odo CLI reference].
