juju

juju [GLOBAL_OPTIONS] <command> [COMMAND_OPTIONS] [ARGUMENTS]

Juju is a powerful command-line interface (CLI) that acts as a client to a Juju controller. It operates primarily through a rich set of subcommands, each dedicated to managing specific aspects of application deployment and operation. GLOBAL_OPTIONS affect the overall client behavior, while COMMAND_OPTIONS and ARGUMENTS are specific to the chosen subcommand.

--debug
    Output highly detailed debug information, useful for troubleshooting Juju operations.

--verbose
    Output more verbose information than default, providing additional insights into Juju's actions.

--quiet
    Suppress all non-error output, useful for scripting or when only critical messages are desired.

--version
    Show the client version information for Juju.

--help, -h
    Display help for the main Juju command or for a specific subcommand (e.g., juju help deploy).

--logging-config <path>
    Specify a path to a custom logging configuration file to override default settings.

--no-browser
    Prevent Juju from attempting to open a web browser for authentication purposes.

--show-log-time
    Include timestamps in log output, aiding in chronological analysis of events.

Juju is an open-source application orchestration and lifecycle management tool developed by Canonical. It allows users to rapidly deploy, integrate, and manage complex applications across various environments, including public clouds (AWS, Azure, GCP), private clouds (OpenStack), bare metal servers, and Kubernetes clusters.

At its core, Juju uses 'charms' – reusable bundles of operational knowledge – to encapsulate the best practices for installing, configuring, connecting, scaling, and maintaining software services. These charms automate day-2 operations, reducing manual effort and ensuring consistent deployments.

Users deploy charms into 'models' which are managed by a 'controller'. Juju handles the provisioning of underlying infrastructure (VMs or containers), networking, and the execution of charm-defined operations. It facilitates the creation of 'relations' between services, allowing them to discover and configure each other automatically. Juju aims to simplify the operational burden of modern distributed applications, making them easier to consume and manage for developers and operations teams alike.

Juju introduces its own set of concepts (controllers, models, charms, relations) which require a learning curve. While it aims for automation, the initial setup and understanding of charm development or selection can be complex. The availability and maintenance quality of charms for specific applications can vary. Managing the Juju controller itself, especially for high-availability, also adds an operational overhead.

Controller: The central management server for Juju, often deployed as a high-availability cluster.
Model: A logical workspace within a controller where applications are deployed, managed, and interact.
Charm: A package of operational knowledge that defines how to deploy, configure, integrate, and operate a specific application or service. Charms are written in Python.
Application: An instance of a deployed charm within a model, representing a running service.
Relation: A connection established between two or more applications, enabling them to communicate and share configuration dynamically.

The Juju client is most commonly installed via Snap on Linux systems: snap install juju --classic. It can also be installed from various system repositories or as a standalone binary for other operating systems like macOS and Windows.

Developed and maintained by Canonical, the company behind Ubuntu, Juju was initially conceived to simplify the deployment and management of applications on cloud infrastructure, particularly OpenStack, AWS, and later Azure and GCP. Its design philosophy centered on 'charms' to encapsulate operational knowledge. With the rise of containerization and Kubernetes, Juju evolved to extend its orchestration capabilities to Kubernetes clusters and bare metal, aiming to provide a consistent application operations experience across diverse computing environments. It remains an active open-source project.

kubectl(1), snap(1), terraform(1), docker-compose(1), cloud-init(1)