# Juju

> Juju is an open source orchestration engine for deploying, integrating, and managing applications across Kubernetes, VMs, and bare metal using software operators called charms.


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## Pages in this subsection

- [Upgrade your Juju deployment from `3.6` to `4.0`](https://documentation.ubuntu.com/juju/4.0/howto/upgrade-your-juju-deployment-from-36-to-40.md): Guide for Juju 3.6 to 4.0 transition: key behavior changes for charm developers and operators, with examples. Prepare your charms and operations for Juju 4.0 with this comprehensive guide.

## Optional

- [Top-level llms.txt](https://documentation.ubuntu.com/juju/4.0/llms.txt): Complete documentation index.