Watchtower supports private Docker image registries. In many cases, accessing a private registry requires a valid username and password (i.e., _credentials_). In order to operate in such an environment, watchtower needs to know the credentials to access the registry. The credentials can be provided to watchtower in a configuration file called `config.json`. There are two ways to generate this configuration file: * The configuration file can be created manually. * Call `docker login ` and share the resulting configuration file. ### Create the configuration file manually Create a new configuration file with the following syntax and a base64 encoded username and password `auth` string: ```json { "auths": { "": { "auth": "XXXXXXX" } } } ``` `` needs to be replaced by the name of your private registry (e.g., `my-private-registry.example.org`) The required `auth` string can be generated as follows: ```bash echo -n 'username:password' | base64 ``` When the watchtower Docker container is started, the created configuration file (`/config.json` in this example) needs to be passed to the container: ```bash docker run [...] -v /config.json:/config.json containrrr/watchtower ``` ### Share the Docker configuration file To pull an image from a private registry, `docker login` needs to be called first, to get access to the registry. The provided credentials are stored in a configuration file called `/.docker/config.json`. This configuration file can be directly used by watchtower. In this case, the creation of an additional configuration file is not necessary. When the Docker container is started, pass the configuration file to watchtower: ```bash docker run [...] -v /.docker/config.json:/config.json containrrr/watchtower ``` When creating the watchtower container via docker-compose, use the following lines: ```yaml version: "3" [...] watchtower: image: index.docker.io/containrrr/watchtower:latest volumes: - /var/run/docker.sock:/var/run/docker.sock - /.docker/config.json:/config.json [...] ``` ## Credential helpers Some private Docker registries (the most prominent probably being AWS ECR) use non-standard ways of authentication. To be able to use this together with watchtower, we need to use a credential helper. To keep the image size small we've decided to not include any helpers in the watchtower image, instead we'll put the helper in a separate container and mount it using volumes. ### Example Example implementation for use with [amazon-ecr-credential-helper](https://github.com/awslabs/amazon-ecr-credential-helper): ```Dockerfile FROM golang:latest ENV CGO_ENABLED 0 ENV REPO github.com/awslabs/amazon-ecr-credential-helper/ecr-login/cli/docker-credential-ecr-login RUN go get -u $REPO RUN rm /go/bin/docker-credential-ecr-login RUN go build \ -o /go/bin/docker-credential-ecr-login \ /go/src/$REPO WORKDIR /go/bin/ ``` and the docker-compose definition: ```yaml version: "3" services: watchtower: image: index.docker.io/containrrr/watchtower:latest volumes: - /var/run/docker.sock:/var/run/docker.sock - /.docker/config.json:/config.json - helper:/go/bin environment: - HOME=/ - PATH=$PATH:/go/bin - AWS_REGION= - AWS_ACCESS_KEY_ID= - AWS_SECRET_ACCESS_KEY= volumes: helper: {} ``` and for `/.docker/config.json`: ```json { "HttpHeaders" : { "User-Agent" : "Docker-Client/19.03.1 (XXXXXX)" }, "credsStore" : "osxkeychain", "auths" : { "xyzxyzxyz.dkr.ecr.eu-north-1.amazonaws.com" : {}, "https://index.docker.io/v1/": {} }, "credHelpers": { "xyzxyzxyz.dkr.ecr.eu-north-1.amazonaws.com" : "ecr-login", "index.docker.io": "osxkeychain" } } ``` *Note:* `osxkeychain` can be changed to your prefered credentials helper.