Kamal

What Kamal is

Kamal is a free, open-source tool from 37signals for deploying containerized web applications in production. It manages applications on bare-metal servers, cloud VMs, Docker containers, and multiple servers, using Docker and SSH connections to listed server IP addresses. The site lists zero-downtime deploys, rolling restarts, asset bridging, remote builds, accessory service management, rollback, and deployment audit logging. Kamal was originally built for Rails applications but works with any web app that can be containerized. With Ruby installed, it can be added using `gem install kamal`; documentation also describes running it in a Docker container, with some limitations. `kamal setup` can install Docker when needed, build and push an image, and start the app. Docker Hub is the default registry, with documentation for local registries, AWS ECR, and GCP Artifact Registry. Secret helpers cover several services, and secrets are kept in a host env file. Custom hooks can abort commands with a non-zero exit code. Linux and macOS are supported.