DCA: Docker Certified Associate

: The commanddocker container logs nginx --volumeswillnotdisplay a list of volumes for a specific container.Thedocker container logscommand shows the logs of a container, which are usually the standard output and standard error of the main process running in the container1.The--volumesflag is not a valid option for this command, and will result in an error message2.To display a list of volumes for a specific container, you can use thedocker inspectcommand with a filter option, such asdocker inspect -f '{{ .Mounts }}' nginx3.This will show the source, destination, mode, type, and propagation of each volume mounted in the container4.Reference:docker container logs,docker container logs nginx --volumes,docker inspect,docker inspect -f '{{ .Mounts }}' nginx

The networkPolicy shown in the image is designed to block traffic from pods lacking the tier: api label, to pods bearing the tier: backend label. This is because the policy is set to matchLabels: tier: backend, and the ingress is set to - from: podSelector: matchLabels: tier: api. Therefore, any traffic that does not match these labels will be blocked.

Isolate containers with a user namespace | Docker Docs

The mnt namespace - Docker Cookbook - Second Edition

Container security fundamentals part 2: Isolation & namespaces

I hope this helps you understand the concept of networkPolicy and how it works with Kubernetes. If you have any other questions related to Docker, please feel free to ask me.

x.500 is not a supported user authentication method for Universal Control Plane (UCP).UCP supports two types of user authentication methods:built-inandexternal1. Built-in authentication uses the UCP's own database to store and verify user credentials.External authentication uses an external LDAP or Active Directory service to manage user accounts and passwords1.x.500 is a standard for directory services, which can be used by LDAP or Active Directory, but it is not a user authentication method by itself2.Reference:

User authentication | Docker Docs

: = The livenessProbe is a mechanism that checks if the container is alive and healthy, and restarts it if it fails1.The orchestrator is the component that manages the deployment and scaling of containers across a cluster of nodes2.The action taken by the orchestrator to fix the unhealthy container isnotto autoscale back and delete the pod, but torecreatethe pod on the same or a different node3. This ensures that the desired number of replicas for the pod is maintained, and that the pod can resume its normal operation. Autoscaling back and deleting the pod would reduce the availability and performance of the service, and would not necessarily alleviate the load.

Configure Liveness, Readiness and Startup Probes | Kubernetes

What is a Container Orchestrator? | Docker

Pod Lifecycle | Kubernetes

I hope this helps you understand the concept of livenessProbe and orchestrator, and how they work with Docker and Kubernetes. If you have any other questions related to Docker, please feel free to ask me.

SELinux could be blocking the operation of setting the system time from inside a Docker container. SELinux is a security mechanism that enforces mandatory access control (MAC) policies on Linux systems. It restricts the actions that processes can perform based on their security contexts, such as user, role, type, and level. By default, SELinux prevents Docker containers from accessing or modifying the host's system time, as this could pose a security risk or cause inconsistency. To allow Docker containers to set the system time, SELinux needs to be configured with the appropriate permissions or labels, or disabled altogether. However, this is not recommended, as it could compromise the security and stability of the system.Reference:

Change system date time in Docker containers without impacting host

Change Date Inside a Docker Container

How to Handle Timezones in Docker Containers

5 ways to change time in Docker container

How to set system time dynamically in a Docker container

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.Reference:Docker Certified Associate Guide,DCA Prep Guide

= This is a function of UCP, as it integrates with Docker Trusted Registry (DTR) to provide built-in security and access control for your images. DTR allows you to enforce security policies and only allow running applications that use Docker images you know and trust. You can sign your images with Docker Content Trust (DCT) to prove their authenticity and integrity.UCP will verify the signatures of the images before deploying them to the cluster12.Reference:

Universal Control Plane overview | dockerlabs

How to Sign Your Docker Images to Increase Trust - How-To Geek