DCA Exam Dumps - Docker Certified Associate Questions and Answers

= The command docker run -v /data:/mydata --mode readonly ubuntu is not valid because it has some syntax errors. The correct syntax for running a container with a bind mount is docker run [OPTIONS] IMAGE [COMMAND] [ARG...]. The errors in the command are:

The option flag for specifying the volume is --volume or -v, not -v. For example, -v /data:/mydata should be --volume /data:/mydata.

The option flag for specifying the mode of the volume is --mount, not --mode. For example, --mode readonly should be --mount type=bind,source=/data,target=/mydata,readonly.

The option flag for specifying the mode of the container is --detach or -d, not --mode. For example, --mode readonly should be --detach.

The correct command for running a container with a bind mount in read-only mode is:

docker run --volume /data:/mydata --mount type=bind,source=/data,target=/mydata,readonly --detach ubuntu

This command will run a container using the ubuntu image and mount the host’s /data directory to the container’s /mydata directory in read-only mode. The container will run in the background (--detach).

 docker run reference | Docker Documentation : [Use bind mounts | Docker Documentation]

The command ‘docker ps http’ is not the correct command to view the list of historical tasks for a service in Docker1.The ‘docker ps’ command is used to list containers1.If you want to view the list of historical tasks for a service, you should use the ‘docker service ps’ command2.Thiscommand lists the tasks that are running as part of the specified services and also shows the task history2.Therefore, to view the list of historical tasks for the ‘http’ service, you should use the command 'docker service ps http’2.

= The role of Control Groups (cgroups) when used with a Docker container is not role-based access control to clustered resources. Cgroups are a feature of the Linux kernelthat allow you to limit, manage, and isolate resource usage of collections of processes running on a system1. Resources are CPU time, system memory, network bandwidth, or combinations of these resources, and so on2. Cgroups allow Docker Engine to share available hardware resources to containers and optionally enforce limits and constraints3. Cgroups can help avoid “noisy neighbor” issues and improve the performance and security of containers4. Role-based access control (RBAC) is a different concept that refers to controlling access to resources based on the roles of individual users within an organization5.

 Lab: Control Groups (cgroups) | dockerlabs : Container security fundamentals part 4: Cgroups | Datadog Security Labs : Docker Namespace Vs Cgroup. Namespace and Cgroup | by MrDevSecOps - Medium : Role-based access control - Wikipedia : Control groups (cgroups) - Learn Docker - Fundamentals of Docker 18.x …

 A liveness probe is a mechanism for indicating your application’s internal health to the Kubernetes control plane. Kubernetes uses liveness probes to detect issues within your pods. When a liveness check fails, Kubernetes restarts the container in an attempt to restore your service to an operational state1. Therefore, the action taken by the orchestrator to fix the unhealthy container is to restart it. References:

Content trust in Docker | Docker Docs

Docker Content Trust: What It Is and How It Secures Container Images

A Practical Guide to Kubernetes Liveness Probes | Airplane

 A node is a physical or virtual machine running Docker Engine in swarm mode1. A node can be either a manager or a worker, depending on its role in the cluster1. A physical machine participating in the swarm is a node, regardless of its role or availability2. References:

How nodes work | Docker Docs

Manage nodes in a swarm | Docker Docs

= Multi-stage builds allow you to use multiple FROM statements in your Dockerfile, each starting a new stage of the build1. This can help you achieve better logical separation of Dockerfile instructions for increased readability, as well as other benefits such as smaller image size, faster build time, and reduced security risks23. By separating your Dockerfile into different stages, you can organize your instructions by their purpose, such as building, testing, or deploying your application. You can also copy only the artifacts you need from one stage to another, leaving behind the unnecessary dependencies or tools1. This can make your Dockerfile easier to read and maintain, as well as improve the performance and security of your final image. References:

Multi-stage builds | Docker Docs

What Are Multi-Stage Docker Builds? - How-To Geek

Multi-stage | Docker Docs

 = The command kubectl describe deployment api displays the events table for the deployment object called api, along with other information such as labels, replicas, strategy, conditions, and pod template. The events table shows the history of actions that have affected the deployment, such as scaling, updating, or creating pods. This can help troubleshoot any issues with the deployment. To see only the events table, you can use the flag --show-events=true with the command. References:

Deployments | Kubernetes

kubectl - How to describe kubernetes resource - Stack Overflow

Kubectl: Get Deployments - Kubernetes - ShellHacks

kubernetes - Kubectl get deployment yaml file - Stack Overflow

= Linux capabilities are a way of restricting the privileges of a process or a container. By default, Docker containers run with a reduced set of capabilities, which means they cannot perform certain operations that require higher privileges, such as setting the system time1. To allow a container to set the system time, you need to grant it the SYS_TIME capability by using the --cap-add option when running the container2. For example, docker run --cap-add SYS_TIME alpine date -s 12:00 would set the system time to 12:00 inside the alpine container3. References: Docker Documentation, Runtime privilege and Linuxcapabilities, Change system date time in Docker containers without impacting host, Is it possible to change time dynamically in docker container?

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 multipleenvironments, 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.