How to share LetsEncrypt certificates in Docker Swarm?

We are using Traefik as reverse proxy, with a Traefik instance on each of our 3 proxy servers, orchestrated by Docker Swarm. We would like to start using LetsEncrypt TLS/SSL certificates for some admin domains, but have trouble with the verification and certificate distribution among those instances.

Docker Swarm volume and secret can not be updated from within a container, and for concurrency reasons you should not share the acme.json file across multiple instances of Traefik.

So how do you make LetsEncrypt work with multiple Traefik instances on Docker Swarm?

You don't/can't. TraefikEE supports this though.