acme-companion is a lightweight companion container for nginx-proxy.

It handles the automated creation, renewal and use of SSL certificates for proxied Docker containers through the ACME protocol.

Features:

• Automated creation/renewal of Let's Encrypt (or other ACME CAs) certificates using acme.sh.
• Let's Encrypt / ACME domain validation through http-01 challenge only.
• Automated update and reload of nginx config on certificate creation/renewal.
• Support creation of Multi-Domain (SAN) Certificates.
• Creation of a strong RFC7919 Diffie-Hellman Group at startup.
• Work with all versions of docker.

Requirements:

• Your host must be publicly reachable on both port 80 and 443.
• Check your firewall rules and do not attempt to block port 80 as that will prevent http-01 challenges from completing.
• For the same reason, you can't use nginx-proxy's HTTPS_METHOD=nohttp.
• The (sub)domains you want to issue certificates for must correctly resolve to the host.
• Your DNS provider must answer correctly to CAA record requests.
• If your (sub)domains have AAAA records set, the host must be publicly reachable over IPv6 on port 80 and 443.

Basic usage (with the nginx-proxy container)

Three writable volumes must be declared on the nginx-proxy container so that they can be shared with the acme-companion container:

• /etc/nginx/certs to store certificates and private keys (readonly for the nginx-proxy container).
• /usr/share/nginx/html to write http-01 challenge files.

Additionally, a fourth volume must be declared on the acme-companion container to store acme.sh configuration and state: /etc/acme.sh.

Please also read the doc about data persistence.

Example of use:

Step 1 - nginx-proxy

Start nginx-proxy with the three additional volumes declared:

$ docker run --detach \
    --name nginx-proxy \
    --publish 80:80 \
    --publish 443:443 \
    --volume certs:/etc/nginx/certs \
    --volume html:/usr/share/nginx/html \
    --volume /var/run/docker.sock:/tmp/docker.sock:ro \
    nginxproxy/nginx-proxy

Binding the host docker socket (/var/run/docker.sock) inside the container to /tmp/docker.sock is a requirement of nginx-proxy.

Step 2 - acme-companion

Start the acme-companion container, getting the volumes from nginx-proxy with --volumes-from:

$ docker run --detach \
    --name nginx-proxy-acme \
    --volumes-from nginx-proxy \
    --volume /var/run/docker.sock:/var/run/docker.sock:ro \
    --volume acme:/etc/acme.sh \
    --env "DEFAULT_EMAIL=mail@yourdomain.tld" \
    nginxproxy/acme-companion

The host docker socket has to be bound inside this container too, this time to /var/run/docker.sock.

Albeit optional, it is recommended to provide a valid default email address through the DEFAULT_EMAIL environment variable, so that Let's Encrypt can warn you about expiring certificates and allow you to recover your account.

Step 3 - proxied container(s)

Once both nginx-proxy and acme-companion containers are up and running, start any container you want proxied with environment variables VIRTUAL_HOST and LETSENCRYPT_HOST both set to the domain(s) your proxied container is going to use.

VIRTUAL_HOST control proxying by nginx-proxy and LETSENCRYPT_HOST control certificate creation and SSL enabling by acme-companion.

Certificates will only be issued for containers that have both VIRTUAL_HOST and LETSENCRYPT_HOST variables set to domain(s) that correctly resolve to the host, provided the host is publicly reachable.

$ docker run --detach \
    --name your-proxied-app \
    --env "VIRTUAL_HOST=subdomain.yourdomain.tld" \
    --env "LETSENCRYPT_HOST=subdomain.yourdomain.tld" \
    nginx

The containers being proxied must expose the port to be proxied, either by using the EXPOSE directive in their Dockerfile or by using the --expose flag to docker run or docker create.

If the proxied container listen on and expose another port than the default 80, you can force nginx-proxy to use this port with the VIRTUAL_PORT environment variable.

Example using Grafana (expose and listen on port 3000):

$ docker run --detach \
    --name grafana \
    --env "VIRTUAL_HOST=othersubdomain.yourdomain.tld" \
    --env "VIRTUAL_PORT=3000" \
    --env "LETSENCRYPT_HOST=othersubdomain.yourdomain.tld" \
    --env "LETSENCRYPT_EMAIL=mail@yourdomain.tld" \
    grafana/grafana

Repeat Step 3 for any other container you want to proxy.

Additional documentation

Please check the docs section.