Kamal is my go-to deployment tool for Rails apps — it handles SSL, zero-downtime deploys, and the proxy with a single kamal deploy command. But officially, Kamal expects you to build and push your own image. It can't deploy an arbitrary public image directly from a registry like Docker Hub or GHCR. Or so I thought. In this post, I'll show you a small trick using a placeholder Dockerfile + Kamal accessories to deploy any publicly available Docker image to a VPS — no custom build required. The Problem Sometimes you just want to run a pre-built public image on your server. In my case, I needed to deploy wg-easy — a WireGuard UI — on a VPS where I already have SSH access. Kamal's normal flow assumes: You have a Dockerfile You build and push your own image to a registry Kamal pulls and deploys that image But for third-party images, step 1 and 2 are unnecessary overhead.…