ecr-login

Login tool for AWS Container Registry.

This is a lightweight golang version of the AWS command-line utility aws ecr get-login, designed to build into a small scratch docker image.

Can also produce output in other formats using golang templates.

Installation

See build or docker image below.

Usage

Login to your AWS Container Registry:

$ eval $(./ecr-login)
WARNING: login credentials saved in /Users/ric/.docker/config.json
Login Succeeded

Alternatively, you can use the included templates to output docker config format directly and redirect output to ~/.docker/config.json or ~/.dockercfg:

$ TEMPLATE=templates/config.tmpl ./ecr-login
{
        "auths": {
                "https://1234567890.dkr.ecr.us-east-1.amazonaws.com": {
                        "auth": "...",
                        "email": "none"
                }
         }
}

Systemd example

This is an example of how I use ecr-login with systemd units on CoreOS:

[Unit]
Description=Example

[Service]
User=core
ExecStartPre=/bin/bash -c 'eval $(docker run rlister/ecr-login:latest)'
ExecStartPre=-/usr/bin/docker rm example
ExecStartPre=/usr/bin/docker pull 1234567890.dkr.ecr.us-east-1.amazonaws.com/example:latest
ExecStart=/usr/bin/docker run --name example 1234567890.dkr.ecr.us-east-1.amazonaws.com/example:latest
ExecStop=/usr/bin/docker stop example

AWS credentials

ecr-login uses the usual AWS environment variables or credentials file. For example, you can set:

AWS_REGION=us-east-1
AWS_ACCESS_KEY_ID=xxx
AWS_SECRET_ACCESS_KEY=xxx

EC2 instance role permissions will be used if available. If AWS_REGION is not set on an ec2 instance, the local region will be inferred from instance metadata.

You will need the correct IAM permissions to authenticate (and then actually pull images from your registry). The easiest method is to add the AWS managed policy AmazonEC2ContainerRegistryReadOnly.

Dependencies

Dependencies are vendored using godep. Install godep with:

go get github.com/tools/godep

then install or update any deps locally with:

go get -u github.com/foo/bar
godep save -r

Build from source

go build ./ecr-login.go

Docker image

version=0.0.1
CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo ecr-login.go
docker build -t rlister/ecr-login:${version} .
docker tag -f rlister/ecr-login:${version} rlister/ecr-login:latest
docker push rlister/ecr-login