Vfrdtyky

I'm not sure if I have already logged in to a docker registry in cmd line by using cmd: docker login. How can you test or see whether you are logged in or not, without trying to push?

Edit

You can login to docker with docker login <repository>

$ 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:

If you are already logged in, the prompt will look like:

$ 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 (myusername):

Answer below is obsolete, docker info no longer shows username information.

Historic

When you are logged in, your username and registry shows up in the docker info command

Like this:

[ciccio@consolecowboy.net ~]$ docker info

Containers: 12

 Running: 2

..etc...

...

Username: francobolli

Registry: https://index.docker.io/v1/

Edit: Note; this only works for index.docker.io repo. Login only stores the credentials on disk when it needs them, for example when running docker pull localhost:5000/image or docker pull quay.io/username/reponame.

Edited after this got pointed out in the comments of this question: how can I tell if I'm logged into a private docker registry

I use one of the following two ways for this check:

1: View config.json file:

In case you are logged in to "private.registry.com" you will see an entry for the same as following in ~/.docker/config.json:

"auths": {

    "private.registry.com": {

        "auth": "gibberishgibberishgibberishgibberishgibberishgibberish"

    }

 }

2: Try docker login once again:

If you are trying to see if you already have an active session with private.registry.com, try to login again:

bash$ docker login private.registry.com

Username (logged-in-user):

If you get an output like the above, it means logged-in-user already had an active session with private.registry.com. If you are just promoted for username instead, that would indicate that there's no active session.

For private registries, nothing is shown in docker info. However, the logout command will tell you if you were logged in:

 $ docker logout private.example.com

 Not logged in to private.example.com

(Though this will force you to log in again.)

At least in "Docker for Windows" you can see if you are logged in to docker hub over the UI. Just right click the docker icon in the windows notification area:

The answers here so far are not so useful:

• 
  docker info no longer provides this info


• 
  docker logout is a major inconvenience - unless you already know the credentials and can easily re-login


• 
  docker login response seems quite unreliable and not so easy to parse by the program

My solution that worked for me builds on @noobuntu's comment: I figured that if I already known the image that I want to pull, but I'm not sure if the user is already logged in, I can do this:

try pulling target image

-> on failure:

   try logging in

   -> on failure: throw CannotLogInException

   -> on success:

      try pulling target image

      -> on failure: throw CannotPullImageException

      -> on success: (continue)

-> on success: (continue)

Use command like below:

docker info | grep 'name'



WARNING: No swap limit support

Username: <strong>jonasm2009</strong>