Docker Note

This contain note that related to docker, for my personal use if I forget the command haha... :D

Authentication

Login

Before push image to registry we need to authenticate docker, to do that use this command

docker login -u username

# Or if you want to login using service account
cat auth.json | docker login -u _json_key --password-stdin https://asia.gcr.io

Docker auth command above which login using service account is an example to login to Google Container Registry (GCR), but before you perform that command you need to download service acount auth.json. The auth.json you can obtain from service account menu in Goggle Cloud Platform (GCP).

Checking Authentication

To checking docker was logged in to some registry you can see it in file config.json

cat ~/.docker/config.json

You will see output like this below.

{
  "auths": {
    "https://index.docker.io/v1/": {}
  },
  "credsStore": "desktop",
  "currentContext": "desktop-linux"
}

It mean that you have authenticate to docker hub. To see cred from docker hub you have beed logged in before use this command. If you have logged in to other registry example GCR you can simply change https://index.docker.io/v1/ to key present in config.josn above

echo "https://index.docker.io/v1/" | docker-credential-desktop get

Logout

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

Change User Container to Non-Root

Why we need to change from Root user to non-root user for security reason.

Check The Image or Container User

Inspect the docker image and see Config.User.

docker inspect image_name

If you get empty string "" or "root" it mean the image/container configured to as root by default. But if you see another value it indicate the non-root user. Or to check the container user you can exec the container and simply run command whoami.

Change Root User to Non-Root

In dockerfile you can add like this

# Add non-root user
RUN adduser -D agungsptr

# Switch to non-root user
USER agungsptr

agungsptr/DockerNote.md