DCA Premium Exam Questions

   = Using network connect to access the container on the bridge network does not accomplish creating a container that is reachable from its host’s network. The network connect command connects a container to an existing network, but it does not expose the container’s ports to the host1. The bridge network is the default network that Docker creates for containers, and it provides isolation from the host network2. To create a container that is reachable from its host’s network, you need to use the host network driver, which disables network isolation and uses the host’s network stack directly3. Alternatively, you can use the port mapping feature to publish specific ports of the container to the host4. References:

• docker network connect | Docker Docs
• Bridge network driver | Docker Docs
• Host network driver | Docker Docs
• Publish ports on the host | Docker Docs

Creating a Dockerfile for each environment, specifying ports and Docker secrets for certificates is not a way to provision configuration to containers at runtime. A Dockerfile is a text document that contains all the commands a user could call on the command line to assemble an image1. A Dockerfile is used to build an image, not to run a container. Once an image is built, the configuration specified in the Dockerfile cannot be changed at runtime. To provision configuration to containers at runtime, you need to use a different mechanism, such as environment variables, command-line arguments, or config maps234. References:

• Dockerfile reference | Docker Docs
• Environment variables in Compose | Docker Docs
• Override the default command | Docker Docs
• Configuration management with Containers | Kubernetes

The command docker Is -a does not list all nodes in a swarm cluster from the command line, but rather lists all containers, both running and stopped, on the current node1. To list all nodes in a swarm cluster, you need to use the command docker node ls from a manager node2. This command shows the node ID, hostname, status, availability, and manager status for each node in the swarm2. You can also use the --filter option to filter the output based on various criteria2. References: Docker Documentation, docker node ls

= Keeping a backup copy of the image on another repository is not how a user can prevent an image, such as ‘nginx:latest’, from being overwritten by another user with push access to the repository. This approach does not prevent the original image from being overwritten, it only provides a way to restore it from another source. However, this may not be reliable or efficient, as the backup repository may not be in sync with the original one, or may not be accessible at all times. To prevent an image from being overwritten by another user, the user can use the DTR web UI to make the tag immutable1. This feature allows the user to lock a specific tag, so that no one can push a new image with the same tag to the repository. This ensures that the image is always consistent and secure1. References:

• Make a tag immutable | Docker Docs