Docker: Login Command – Registry Login & Logout

To start using a private Docker Registry a user usually should run the docker login command and set a username and password that will be cached locally.

If a user tries to docker pull or docker push an image from/to a private Docker Registry, without having run the docker login command in advance, he may receive the “unauthorized: authentication required” error.

This guide explains how to log in and how to log out of a private Docker Registry from the command line using the docker login and docker logout commands.

Cool Tip: Pull an image from Docker Registry! Read More →

Docker Login Command

By default, if you don’t specify a private registry, the docker login command will try to log in to a Docker Hub’s public registry located at https://registry-1.docker.io:

$ docker login
Login with your Docker ID to push and pull images from Docker Hub.
If you don't have a Docker ID, head over to https://hub.docker.com to create one.
Username: foo
Password:

Log in to a private Docker Registry (you will be prompted for credentials):

$ docker login private.registry.tld:8080
Username: foo
Password:

Log in to a private Docker Registry with a username and password passed through the command line:

$ docker login private.registry.tld:8080 -u <username> -p <password>

Alternatively you can read a password from a file, and pass it to the docker login command using STDIN (handy for automations):

$ cat pwd.txt | docker login private.registry.tld:8080 -u <username> --password-stdin

When you log in, the command stores base64 encoded username:password pair in $HOME/.docker/config.json on Linux or %USERPROFILE%/.docker/config.json on Windows:

$ cat $HOME/.docker/config.json
{
  "auths": {
      "https://private.registry.tld:8080/v2/": {
          "auth": "dXNlcm5hbWU6cGFzc3dvcmQ="
      }
  }
}

Cool Tip: Enter a running Docker container and start a bash session! Read More →

Docker Logout Command

The docker logout command is used to log out of a Docker Registry:

$ docker logout private.registry.tld:8080