Pass the Docker Certified Associate DCA Questions and answers with ValidTests

A DTR security scan will not detect image configuration poor practices, such as exposed ports or inclusion of compilers in production images. A DTR security scan is designed to discover vulnerabilities in the images based on the MITRE CVE or NIST NVD databases1. It does not check the image configuration or best practices. To check the image configuration and best practices, you can use other tools, such as Dockerfile Linter) or Docker Bench for Security). References: Vulnerability scanning must be enabled for all repositories in the Docker Trusted Registry (DTR) component of Docker Enterprise), Dockerfile Linter), Docker Bench for Security)

= A DTR security scan will detect private keys copied to the image. DTR security scan is a feature of Docker Trusted Registry (DTR) that scans images to detect any security vulnerability1. DTR security scan uses the open source tool SecretScanner2 to find unprotected secrets in container images or file systems. SecretScanner can match the contents of images against a database of approximately 140 secret types, including private keys3. Therefore, if an image contains private keys, DTR security scan will report them as potential secrets and alert the user to remove them from the image. References:

Scan images for vulnerabilities | Docker Docs

GitHub - deepfence/SecretScanner: :unlock: Find secrets and passwords …

SecretScanner/deepfence_secret_scanner.py at main · deepfence/SecretScanner

While creating a Dockerfile for each environment is a possible solution, it is not the most efficient or scalable way to provision configuration to containers at runtime. Docker provides several mechanisms to inject configuration into containers at runtime, such as environment variables, command line arguments, Docker secrets for sensitive data, or even configuration files mounted as volumes. These methods allow the same Docker image to be used across multiple environments, promoting immutability and consistency across your deployments. Creating a separate Dockerfile for each environment would mean maintaining multiple versions of the Dockerfile, which could lead to inconsistencies and is generally not a recommended practice.

= Distributing seven managers across three datacenters or availability zones as 3-3-1 is not the best way to ensure high availability and fault tolerance. This is because if one of the datacenters with three managers fails, the remaining four managers will not have a quorum to elect a leader and continue the swarm operations. A quorum is the minimum number of managers that must be available to maintain the swarm state, and it is calculated as (N/2) + 1, where N is the total number of managers1. For seven managers, the quorum is five, so losing three managers will cause the swarm to lose the quorum. A better way to distribute seven managers across three datacenters or availability zones is 2-2-3, which will allow the swarm to survive the failure of any one datacenter2. References:

Administer and maintain a swarm of Docker Engines

Distribute manager nodes across multiple AZ

= The command docker network create -d overlay --secure  will not ensure that overlay traffic between service tasks is encrypted. The --secure option is not a valid flag for the docker network create command1. To enable encryption for an overlay network, you need to use the --opt encrypted flag instead23. This will create IPSEC tunnels between the nodes where the service tasks are scheduled, using the AESalgorithm in GCM mode2. You can verify if an overlay network is encrypted by checking if the IPSEC tunnels were created using tools like netstat4. References:

1: docker network create | Docker Docs

2: Encrypt traffic on an overlay network | Docker Docs

3: Overlay network driver | Docker Docs

4: Docker: How to verify if an overlay network is encrypted - Stack Overflow

Docker uses cgroups, a Linux kernel feature, to limit the resources a container can use.This includes CPU and memory resources12.For instance, Docker can limit a container’s CPU usage to the equivalent of a single CPU core on the Docker host system2.Similarly, Docker can limit a container’s memory usage1.However, to use these features, the Docker host must have cgroup memory and swap accounting enabled1.Therefore, cgroups can indeed limit a Docker container’s access to host resources such as CPU and memory12.

The statement is correct. In the provided Kubernetes YAML, it’s defined that traffic sent to the IP of this service on port 8080 will be routed to port 80 in a random pod with the label app: nginx. This is because it’s a ClusterIP service type which is meant for internal communication within the cluster, and it uses selectors to route traffic to the correct pods. References: Docker Certified Associate Guide, DCA Prep Guide

 This command will not display a list of volumes for a specific container, as it will show detailed information on the container itself, such as its configuration, network settings, state, and log path1. To display a list of volumes for a specific container, you need to use the --format option with a custom template that filters the output by the Mounts field2. For example, the following command will show the source and destination of the volumes mounted in the nginx container:

docker container inspect --format=' { {range .Mounts}} { {.Source}} -> { {.Destination}} { {end}}' nginx References:

docker container inspect | Docker Docs

How to Use Docker Inspect Command - Linux Handbook

= Authentication is not a type of Linux kernel namespace that provides container isolation. Namespaces are a feature of the Linux kernel that partitions kernel resources such that one set of processes sees one set of resources and another set of processes sees a different set of resources. Docker uses six different namespaces to isolate containersfrom the host and from each other: PID, USER, UTS, IPC, MNT, and NET12. Authentication is not one of them. Authentication is a process of verifying the identity of a user or a system, which is usually done by using credentials such as passwords, tokens, or certificates. Authentication does not directly affect the isolation of containers, although it can be used to control access to them. References:

Docker security | Docker Docs

Securing Docker Containers with Linux Kernel Features | Infosec