# Reference Technical specifications, APIs, and comprehensive details of all Juju components. ## Platform Juju is an orchestration platform that includes the CLI client, agent binaries, and supporting infrastructure for managing cloud deployments. - [Juju](https://documentation.ubuntu.com/juju/4.0/reference/juju.md#juju) ## Cloud and Charmhub In Juju, deployments draw from two external sources. Clouds provide compute resources for your infrastructure. Charmhub provides charms – operators for deploying and managing applications. - [Cloud](https://documentation.ubuntu.com/juju/4.0/reference/cloud.md#cloud) - [Credential](https://documentation.ubuntu.com/juju/4.0/reference/credential.md#credential) - [Simplestreams metadata](https://documentation.ubuntu.com/juju/4.0/reference/metadata.md#metadata) - [Charmhub](https://charmhub.io/) - [`juju-controller` charm](https://charmhub.io/juju-controller) ## Client In Juju, you interact with these resources through clients – command-line and web interfaces for managing controllers, models, and deployments. - [Client](https://documentation.ubuntu.com/juju/4.0/reference/client.md#client) - [juju CLI](https://documentation.ubuntu.com/juju/4.0/reference/juju-cli.md#juju-cli) - [juju web CLI](https://documentation.ubuntu.com/juju/4.0/reference/juju-web-cli.md#juju-web-cli) - [juju-dashboard (The Juju dashboard)](https://documentation.ubuntu.com/juju/4.0/reference/juju-dashboard.md#juju-dashboard) - [juju-db-repl](https://documentation.ubuntu.com/juju/4.0/reference/juju-db-repl.md#juju-db-repl) - [juju web CLI](https://documentation.ubuntu.com/juju/4.0/reference/juju-web-cli.md#juju-web-cli) - [jujuc](https://documentation.ubuntu.com/juju/4.0/reference/jujuc.md#jujuc) - [jujud](https://documentation.ubuntu.com/juju/4.0/reference/jujud.md#jujud) - [Pebble](https://documentation.ubuntu.com/juju/4.0/reference/pebble.md#pebble) ## Controller Clients connect to a controller – the central management service that coordinates between clouds, Charmhub, and your deployed resources. - [Action](https://documentation.ubuntu.com/juju/4.0/reference/action.md#action) - [Agent](https://documentation.ubuntu.com/juju/4.0/reference/agent.md#agent) - [Application](https://documentation.ubuntu.com/juju/4.0/reference/application.md#application) - [Bundle](https://documentation.ubuntu.com/juju/4.0/reference/bundle.md#bundle) - [Charm](https://documentation.ubuntu.com/juju/4.0/reference/charm.md#charm) - [Client](https://documentation.ubuntu.com/juju/4.0/reference/client.md#client) - [Cloud](https://documentation.ubuntu.com/juju/4.0/reference/cloud.md#cloud) - [Configuration](https://documentation.ubuntu.com/juju/4.0/reference/configuration.md#configuration) - [Constraint](https://documentation.ubuntu.com/juju/4.0/reference/constraint.md#constraint) - [Controller](https://documentation.ubuntu.com/juju/4.0/reference/controller.md#controller) - [Credential](https://documentation.ubuntu.com/juju/4.0/reference/credential.md#credential) - [Database](https://documentation.ubuntu.com/juju/4.0/reference/database.md#database) - [Log](https://documentation.ubuntu.com/juju/4.0/reference/log.md#log) - [Telemetry](https://documentation.ubuntu.com/juju/4.0/reference/telemetry.md#telemetry) - [High availability (HA)](https://documentation.ubuntu.com/juju/4.0/reference/high-availability.md#high-availability) - [Scaling](https://documentation.ubuntu.com/juju/4.0/reference/scaling.md#scaling) ## Users Controller access requires user authentication. User accounts provide authentication and authorization for managing Juju resources. - [User](https://documentation.ubuntu.com/juju/4.0/reference/user.md#user) ## Infrastructure and applications Once authenticated, users work with deployments. Within a controller, deployments are organized into models – logical containers for applications, infrastructure, and their supporting components. Each model draws resources from a single cloud. - [Model](https://documentation.ubuntu.com/juju/4.0/reference/model.md#model) Models contain applications deployed from charms and composed of units (individual instances). - [Charm](https://documentation.ubuntu.com/juju/4.0/reference/charm.md#charm) - [Application](https://documentation.ubuntu.com/juju/4.0/reference/application.md#application) - [Unit](https://documentation.ubuntu.com/juju/4.0/reference/unit.md#unit) Applications connect to each other through relations endpoints – integration points between compatible interfaces. Offers enable cross-model relations. - [Relation (integration)](https://documentation.ubuntu.com/juju/4.0/reference/relation.md#relation) - [Offer](https://documentation.ubuntu.com/juju/4.0/reference/offer.md#offer) Applications are managed through configuration, secrets, actions, and scripts, and support scaling and high availability. Charms may require resources. - [Configuration](https://documentation.ubuntu.com/juju/4.0/reference/configuration.md#configuration) - [Resource (charm)](https://documentation.ubuntu.com/juju/4.0/reference/resource-charm.md#charm-resource) - [Secret](https://documentation.ubuntu.com/juju/4.0/reference/secret.md#secret) - [Action](https://documentation.ubuntu.com/juju/4.0/reference/action.md#action) - [Script](https://documentation.ubuntu.com/juju/4.0/reference/script.md#script) - [High availability (HA)](https://documentation.ubuntu.com/juju/4.0/reference/high-availability.md#high-availability) - [Scaling](https://documentation.ubuntu.com/juju/4.0/reference/scaling.md#scaling) Supporting infrastructure – machines, storage volumes, network spaces and subnets, and availability zones – is provisioned from the cloud. Constraints and placement directives control how resources are selected and allocated. SSH keys provide access. - [Machine](https://documentation.ubuntu.com/juju/4.0/reference/machine.md#machine) - [Storage](https://documentation.ubuntu.com/juju/4.0/reference/storage.md#storage) - [Constraint](https://documentation.ubuntu.com/juju/4.0/reference/constraint.md#constraint) - [Placement directive](https://documentation.ubuntu.com/juju/4.0/reference/placement-directive.md#placement-directive) - [Space](https://documentation.ubuntu.com/juju/4.0/reference/space.md#space) - [Subnet](https://documentation.ubuntu.com/juju/4.0/reference/subnet.md#subnet) - [Zone](https://documentation.ubuntu.com/juju/4.0/reference/zone.md#zone) - [SSH key](https://documentation.ubuntu.com/juju/4.0/reference/ssh-key.md#ssh-key) On each machine, agents (`jujud` on machines, `containeragent` on Kubernetes) execute charm code through hooks. Charms use hook commands (provided by `jujuc`) to interact with Juju. On Kubernetes, `containeragent` also orchestrates workload containers using Pebble. - [Agent](https://documentation.ubuntu.com/juju/4.0/reference/agent.md#agent) - [jujud](https://documentation.ubuntu.com/juju/4.0/reference/jujud.md#jujud) - [Hook](https://documentation.ubuntu.com/juju/4.0/reference/hook.md#hook) - [Hook command](https://documentation.ubuntu.com/juju/4.0/reference/hook-command.md#hook-command) - [jujuc](https://documentation.ubuntu.com/juju/4.0/reference/jujuc.md#jujuc) - [containeragent](https://documentation.ubuntu.com/juju/4.0/reference/containeragent.md#containeragent) - [Pebble](https://documentation.ubuntu.com/juju/4.0/reference/pebble.md#pebble) Lifecycle management Removing and upgrading are cross-cutting operations that apply across multiple resource types – from individual units and applications to entire models and controllers. - [Telemetry](https://documentation.ubuntu.com/juju/4.0/reference/telemetry.md#telemetry) - [Removing things](https://documentation.ubuntu.com/juju/4.0/reference/removing-things.md#removing-things) - [Upgrading things](https://documentation.ubuntu.com/juju/4.0/reference/upgrading-things.md#upgrading-things)