DCA Exam Dumps - Docker Certified Associate (DCA) Exam

= The command docker run -add-volume /data /mydata -read-only ubuntu will not mount the host’s /data directory to the ubuntu container in read-only mode. The reason is that the command has several syntax errors and invalid options. The correct command to mount a host directory to a container in read-only mode is docker run --mount type=bind,source=/data,target=/mydata,readonly ubuntu12. The command docker run -add-volume /data /mydata -read-only ubuntu has the following problems:

The option -add-volume is not a valid option for docker run. The valid options for mounting a volume or a bind mount are --mount or -v12.

The option -read-only is not a valid option for docker run. The valid option for making the container’s root filesystem read-only is --read-only3. However, this option will not affect the mounted volumes or bind mounts, which have their own readonly option12.

The argument /data /mydata is not a valid argument for docker run. The argument for docker run should be the command to run inside the container, such as bash or ping4. The source and target of the volume or bind mount should be specified in the --mount or -v option, separated by a colon12.

Therefore, the command docker run -add-volume /data /mydata -read-only ubuntu will not work as intended, and will likely produce an error message or an unexpected result. References:

Use bind mounts

Use volumes

docker run

Docker run reference

 The command docker service create -name dns-cache -p 53:53 -service udp dns-cache is not valid because it has some syntax errors. The correct syntax for creating a swarm service is docker service create [OPTIONS] IMAGE [COMMAND] [ARG...]. The errors in the command are:

There should be a space between the option flag and the option value. For example, -name dns-cache should be -name dns-cache.

The option flag for specifying the service mode is -mode, not -service. For example, -service udp should be -mode udp.

The option flag for specifying the port mapping is --publish or -p, not -p. For example, -p 53:53 should be --publish 53:53.

The correct command for creating a swarm service that only listens on port 53 using the UDP protocol is:

docker service create --name dns-cache --publish 53:53/udp dns-cache

This command will create a service called dns-cache that uses the dns-cache image and exposes port 53 on both the host and the container using the UDP protocol.

[docker service create | Docker Documentation] : [Publish ports for services | Docker Documentation]

= LDAP is a supported user authentication method for Universal Control Plane (UCP). UCP has its own built-in authentication mechanism and integrates with LDAP and Active Directory. It also supports Role Based Access Control (RBAC) and Docker Content Trust. UCP allows you to configure LDAP as an authentication method and connect it toyour LDAP server. You need to provide the LDAP URL, the base DN, the bind DN and password, and the user and group search settings12. References:

SAML | Docker Docs

Universal Control Plane overview | dockerlabs

 = I cannot give you a comprehensive explanation, but I can tell you that the question is about Docker Swarm, which is a native clustering solution for Docker1. Docker Swarm allows you to create a group of Docker hosts, called nodes, that work together as a single virtual system1. Nodes can be either managers or workers. Managers are responsible for maintaining the cluster state and orchestrating services, while workers are responsible for running the tasks assigned by managers1. A swarm cluster should have an odd number of managers to avoid split-brain scenarios and ensure high availability2. However, having too many managers can also degrade performance and increase the risk of failures2. Therefore, the recommended number of managers is between 3and 72. The solution suggests distributing the 7 managers across 3 datacenters or availability zones as 5-1-1, meaning 5 managers in one zone, and 1 manager in each of the other two zones. This may not be the optimal distribution, as it creates a single point of failure in the zone with 5 managers. If that zone goes down, the remaining 2 managers will not be able to form a quorum and the cluster will become unavailable3. A better distribution may be 3-2-2 or 2-2-2-1, as they provide more redundancy and resilience3. You will need to understand how Docker Swarm works and how to design a highly available cluster to answer this question correctly. References: You can find some useful references for this question in the following links:

Docker Swarm overview

Swarm mode key concepts

Swarm mode best practices

= The strategy of creating a PersistentVolume with hostPath and a PersistentVolumeClaim to mount the /data directory on your laptop into a container will not work, because hostPath volumes are only suitable for single node testing or development. They are not portable across nodes and do not support dynamic provisioning. If you want to mount a local directory from your laptop into a Kubernetes pod, you need to use a different type of volume, such as NFS, hostPath CSI, or minikube. Alternatively, you can copy the files from your laptop to the container using kubectl cp command. References:

Volumes | Kubernetes

Configure a Pod to Use a PersistentVolume for Storage | Kubernetes

Mount a local directory to kubernetes pod - Stack Overflow

Kubernetes share a directory from your local system to kubernetes container - Stack Overflow

How to Mount a Host Directory Into a Docker Container

= Mirroring the engineering/api repository to one of the user’s own private repositories will not grant them read/write access to the original repository. Mirroring is a feature that allows users to automatically sync images from one repository to another, either within the same DTR or across different DTRs. Mirroring does not affect the permissions or roles of the users or teams associated with the source or destination repositories. To grant a user read/write access to the engineering/api repository, the user needs to be added to a team that has the appropriate role for that repository, or the repository needs to be configured with the appropriate visibility and access settings. References:

Mirror repositories

Manage access to repositories

Manage teams

= Setting and exporting the IGNORE_TLS environment variable on the command line is not a way to configure the Docker engine to use a registry without a trusted TLS certificate. This environment variable is not recognized by Docker and has no effect on the TLS verification process1. To use a registry without a trusted TLS certificate, you need to either add the certificate to the system or Docker-specific trust store, or configure the Docker daemon to allow insecure registries23. References:

Environment variables | Docker Docs

Verify repository client with certificates | Docker Docs

Test an insecure registry | Docker Docs

= I cannot give you a comprehensive explanation, but I can tell you that the command is not correct. The docker network create command is used to create a new network, not to encrypt an existing one1. The -d option specifies the driver to use for the network,which in this case is overlay1. The overlay driver enables multi-host networking for swarm services2. The --secure option is not a valid option for the docker network create command1. To ensure that overlay traffic between service tasks is encrypted, you need to use the --opt encrypted option2. For example, docker network create -d overlay --opt encrypted my-net will create an overlay network named my-net with encryption enabled2. You will need to understand how to use the docker network command and how to configure overlay networks to answer this question correctly. References:

Docker network create command documentation: 1

Overlay network encryption documentation: 2

I hope this helps you prepare for your DCA exam. If you want to practice more questions, you can check out some of the online courses that offer practice exams, such as 3, 4, 5, 6, and [7]. Good luck!😊