The command docker inspect nodes will not list all nodes in a swarm cluster from the command line. This is because docker inspect requires one or more names or IDs of the objects to inspect1. To list all nodes in a swarm cluster, you need to use the command docker node ls2, which will display information such as node ID, hostname, status, availability, and role3. References:

• docker inspect | Docker Docs
• docker node ls | Docker Docs
• How to list nodes in a Docker swarm cluster

Docker Content Trust (DCT) is a feature that allows users to verify the integrity and publisher of container images they pull or deploy from a registry server, signed on a Notary server1. DCT is enabled by setting the environment variable DOCKER_CONTENT_TRUST=1 on the Docker client. When DCT is enabled, the Docker client will only pull, run, or build images that have valid signatures for a specific tag2. However, DCT does not apply to the docker image import command, which allows users to import an image or a tarball with a repository and tag from a file or STDIN3. Therefore, if myorg/myimage:1.0 is unsigned, Docker will not block the docker image import myorg/myimage:1.0 command, even if DCT is enabled. This is because the docker image import command does not interact with a registry or a Notary server, and thus does not perform any signature verification. However, this also means that the imported image will not have any trust data associated with it, and it will not be possible to push it to a registry with DCT enabled, unless it is signed with a valid key. References:

• Content trust in Docker
• Automation with content trust
• [docker image import]
• [Content trust and image tags]

The command docker system events --filter splunk will not configure a Docker container to export container logs to the logging solution. The command docker system events will display real-time events from the Docker daemon, such as container creation, start, stop, etc. The --filter option will filter the events by various criteria, such as type, label, name, etc. However, there is no filter for splunk, and even if there was, it would only show the events related to Splunk, not the container logs. To configure a Docker container to export container logs to Splunk, you need to use the Splunk logging driver, which is a plugin that sends container logs to HTTP Event Collector in Splunk Enterprise and Splunk Cloud. You can use the --log-driver and --log-opt options when creating or running a container to specify the Splunk logging driver and its options, such as the Splunk token, URL, source, sourcetype, index, etc. Alternatively, you can configure the Splunk logging driver as the default logging driver for the Docker daemon by setting the log-driver and log-opts keys in the daemon.json file and restarting Docker. References:

• docker system events
• Splunk logging driver
• How to send Docker containers logs to Splunk?

 A DTR security scan will detect licenses for known third party binary components. This is because DTR security scan uses a database of vulnerabilities and licenses that is updated regularly from Docker Server1. DTR security scan can identify the components and versions of the software packages that are present in the image layers, and report any known vulnerabilities or licenses associated with them2. This can help users to comply with the licensing requirements and avoid potential legal issues3. References:

• Set up vulnerability scans | Docker Docs
• Scan images for vulnerabilities | Docker Docs
• Container Security 101 — Scanning images for Vulnerabilities

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. This command 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.

= 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

= The conditions are sufficient for Kubernetes to dynamically provision a persistentVolume, because they include a default storageClass and a persistentVolumeClaim. A storageClass defines which provisioner should be used and what parameters should be passed to that provisioner when dynamic provisioning is invoked. A persistentVolumeClaim requests a specific size, access mode, and storageClass for the persistentVolume. If a persistentVolume that satisfies the claim exists or can be provisioned, the persistentVolumeClaim is bound to that persistentVolume. A default storageClass means that any persistentVolumeClaim that does not specify a storageClass will use the default one. Therefore, the conditions in the question are enough to enable dynamic provisioning of storage volumes on-demand. References:

• Dynamic Volume Provisioning | Kubernetes
• Persistent volumes and dynamic provisioning | Google Kubernetes Engine …

 = Uninstalling the ‘docker-ce’ package before installing the ‘docker-ee’ package will not upgrade Docker Engine CE to Docker Engine EE. It will only remove the existing Docker Engine CE installation and install a new Docker Engine EE installation. This means that any existing containers, images, volumes, networks, and other Docker resources will be lost. To upgrade Docker Engine CE to Docker Engine EE without losing any data, you need to use the migration tool provided by Docker1 or follow the steps described in the Docker documentation2 or other online guides34. References:

• 1: Migrate to Engine 1.10 | Docker Docs
• 2: Install Docker Engine | Docker Docs
• 3: Switching Docker 18.09 Community Edition to Enterprise Engine with no …
• 4: How to upgrade Docker 18.09 Community Edition to Docker Enterprise 18.09

 Label constraints can be used to schedule containers to meet the security policy requirements. Label constraints are a way to specify which nodes a service can run on based on the labels assigned to the nodes. Labels are key-value pairs that can be attached to any node in the swarm. For example, you can label nodes as development or production depending on their intended use. Then, you can use the --constraint option when creating or updating a service to filter the nodes based on their labels. For example, to run a service only on development nodes, you can use:

docker service create --constraint 'node.labels.environment == development' ...

To run a service only on production nodes, you can use:

docker service create --constraint 'node.labels.environment == production' ...

This way, you can ensure that development and production containers run on separate nodes in the swarm, as required by the security policy. References:

• Using placement constraints with Docker Swarm
• Multiple label placement constraints in docker swarm
• Machine constraints in Docker swarm
• How can set service constraint to multiple value

 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

The command docker run --log-driver=splunk for every container at run time will configure a Docker container to export container logs to the logging solution. The reason is that the --log-driver option specifies the logging driver for the container, which determines how the container logs are handled1. The splunk logging driver is a plugin that sends container logs to HTTP Event Collector in Splunk Enterprise and Splunk Cloud2. To use the splunk logging driver, you also need to provide some additional options with the --log-opt flag, such as the Splunk token, URL, source, sourcetype, index, etc2. For example, to run a container with the splunk logging driver and send the logs to a Splunk instance with the URL https://splunk.example.com:8088  and the token 176fabb6-7811-4b3a-8ba0-4d49302e50f2, you can use:

docker run --log-driver=splunk --log-opt splunk-token=176fabb6-7811-4b3a-8ba0-4d49302e50f2 --log-opt splunk-url=https://splunk.example.com:8088 ...

This way, you can configure a Docker container to export container logs to Splunk, which is a centralized logging solution. Alternatively, you can also configure the splunk logging driver as the default logging driver for the Docker daemon by setting the log-driver and log-opts keys in the daemon.json file and restarting Docker3. This will apply the splunk logging driver to all containers unless overridden by the --log-driver option. References:

• Configure logging drivers
• Splunk logging driver
• Set the logging driver for the Docker daemon

Docker allows the use of insecure registries through a specific configuration in the Docker daemon. By listing the insecure registries in the ‘daemon.json’ configuration file under the ‘insecure-registries’ key, Docker can interact with these registries even without a trusted TLS certificate1. This is particularly useful when setting up a private Docker registry1. However, it’s important to note that this configuration bypasses the security provided by TLS, and should be used with caution1.

= 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

= 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

The statement is not entirely correct. In Kubernetes, a service of type ClusterIP routes traffic sent to its IP address to the pods selected by its label selector1. However, the port to which the traffic is routed in the pod is determined by the targetPort specified in the service definition1. If targetPort is not specified, it defaults to being the same as the port field1. In the provided YAML snippet, there is no targetPort specified for port 80, so we cannot confirm that the traffic will be routed to port 8080 in the pod. Therefore, without additional information about the pod configuration, we cannot verify the provided solution statement1.

= Mounting the configuration file directly into the appropriate pod and container using the .spec.containers.configMounts key is not a valid way to provide a configuration file to a container at runtime. The .spec.containers.configMounts key does not exist in the Kubernetes API1. The correct way to provide a configuration file to a container at runtime is to use a ConfigMap2. A ConfigMap is a Kubernetes object that stores configuration data as key-value pairs. You can create a ConfigMap from a file, and then mount the ConfigMap as a volume into the pod and container. The configuration file will be available as a file in the specified mount path3. Alternatively, you can also use environment variables to pass configuration data to a container from a ConfigMap4. References:

• PodSpec v1 core
• Configure a Pod to Use a ConfigMap
• Populate a Volume with data stored in a ConfigMap
• Define Container Environment Variables Using ConfigMap Data

 = The command ‘docker service ps http’ will list the tasks that are running as part of the ‘http’ service, as well as the task history1. The task history shows the previous states of the tasks, such as running, shutdown, rejected, etc. This can help you troubleshoot why the service is not registering as healthy, by looking at the current state, error, and ports of each task1. References:

• docker service ps | Docker Docs
• Docker Certified Associate Guide
• DCA Prep Guide

 = 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

= 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 containers from 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

The networking drivers that allow you to enable multi-host network connectivity between containers are bridge, macvlan, ipvlan, and overlay. These drivers create networks that can span multiple Docker hosts, and therefore enable containers on different hosts to communicate with each other. The other drivers, such as host, user-defined, and none, create networks that are either isolated or limited to a single host. Here is a brief overview of each driver and how it supports multi-host networking:

•bridge: The bridge driver creates a network that connects containers on the same host using a Linux bridge. However, it can also be used to create a network that connects containers across multiple hosts using an external key-value store, such as Consul, Etcd, or ZooKeeper. This feature is deprecated and not recommended, as it requires manual configuration and has some limitations. The preferred driver for multi-host networking is overlay1.

•macvlan: The macvlan driver creates a network that assigns a MAC address to each container, making it appear as a physical device on the network. This allows the containers to communicate with other devices on the same network, regardless of the host they are running on. The macvlan driver can also use 802.1q trunking to create sub-interfaces and isolate traffic between different networks2.

•ipvlan: The ipvlan driver creates a network that assigns an IP address to each container, making it appear as a logical device on the network. This allows the containers to communicate with other devices on the same network, regardless of the host they are running on. The ipvlan driver can also use different modes, such as l2, l3, or l3s, to control the routing and isolation of traffic between different networks3.

•overlay: The overlay driver creates a network that connects multiple Docker daemons together using VXLAN tunnels. This allows the containers to communicate across different hosts, even if they are on different networks. The overlay driver also supports encryption, load balancing, and service discovery. The overlay driver is the default and recommended driver for multi-host networking, especially for Swarm services4.

References:

•Use bridge networks

•Use macvlan networks

•Use ipvlan networks

•Use overlay networks

 = The command ‘docker service inspect http’ will display detailed information on the ‘http’ service, such as its ID, name, mode, replicas, container spec, networks, ports, etc. However, it will not show the list of historical tasks for the service. To view the list of tasks, you need to use the command ‘docker service ps http’, which will show the ID, name, image, node, desired state, current state, and error of each task12. References:

• 1: docker service inspect | Docker Docs
• 2: docker service ps | Docker Docs

= 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

 = 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 3 and 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 statement is correct. In the provided Docker Compose file, a health check is defined for the service “app”. It uses curl to perform a health check on the application every 10 seconds (as specified by the “interval” parameter). If it fails three times (as specified by the “retries” parameter), then the container is marked as unhealthy. A health check is a way of checking the health of a running container and applying actions based on the result1. It can be used to monitor the status of the service and restart the container if it becomes unhealthy2. References:

• Compose file version 3 reference | Docker Docs
• Docker Compose & Health Checks – Gabriel’s World

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.

Docker’s bridge network allows containers connected to the same bridge network to communicate, while providing isolation from containers that aren’t connected to that bridge network1. By using the network attach command, you can connect a container to the bridge network, making it reachable from the host’s network12. However, it’s important to note that containers on the default bridge network can only access each other by IP addresses, unless you use the --link option, which is considered legacy2. For better isolation and automatic DNS resolution between containers, it’s recommended to use user-defined bridge networks12.

Adding a new user to the engineering organization in DTR will not automatically grant them read/write access to the engineering/api repository. This is because the repository permissions are not inherited from the organization level, but are configured separately for each repository. Therefore, to grant read/write access to the new user, you need to add them directly to the list of users with read/write access under the repository’s Permissions tab. References:

• Docker Trusted Registry - Manage access to repositories
• Docker Certified Associate (DCA) Study Guide - Domain 3: Image Creation, Management, and Registry

https://docs.docker.com/ee/dtr/user/manage-repos/#manage-access-to-repositories

https://success.docker.com/certification/study-guides/dca-study-guide#domain-3-image-creation-management-and-registry-20-of-exam

 The set of commands docker port inspect and docker container inspect will not identify the published port(s) for a container. The reason is that there is no such command as docker port inspect. The correct command to inspect the port mappings of a container is docker port1. The command docker container inspect can also show the port mappings of a container, but it will display a lot of other information as well, so it is not as concise as docker port2. To identify the published port(s) for a container, you can use either of these commands:

• docker port CONTAINER will list all the port mappings of the container1.
• docker port CONTAINER PRIVATE_PORT will list only the port mapping of the specified private port of the container1.
• docker container inspect --format=' { {.NetworkSettings.Ports}}' CONTAINER will list only the port mappings of the container in a JSON format23.

For example, if you have a container named web that publishes port 80 to port 8080 on the host, you can use any of these commands to identify the published port:

$ docker port web

80/tcp -> 0.0.0.0:8080

$ docker port web 80

0.0.0.0:8080

$ docker container inspect --format=' { {.NetworkSettings.Ports}}' web

map[80/tcp:[map[HostIp:0.0.0.0 HostPort:8080]]]

References:

• docker port
• docker container inspect
• How can I grab exposed port from inspecting docker container?

 In the context of a swarm mode cluster, an instance of the Docker engine participating in the swarm is indeed a node1. A node can be either a manager or a worker, depending on the role assigned by the swarm manager2. A manager node handles the orchestration and management of the swarm, while a worker node executes the tasks assigned by the manager2. A node can join or leave a swarm at any time, and the swarm manager will reconcile the desired state of the cluster accordingly1. References:

• 1: Swarm mode overview | Docker Docs
• 2: Manage nodes in a swarm | Docker Docs

The command docker container logs nginx –volumes will not display a list of volumes for a specific container. The docker container logs command shows the logs of a container, which are usually the standard output and standard error of the main process running in the container1. The –volumes flag 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 the docker inspect command with a filter option, such as docker inspect -f '{{ .Mounts }}' nginx3. This will show the source, destination, mode, type, and propagation of each volume mounted in the container4. References: docker container logs, docker container logs nginx –volumes, docker inspect, docker inspect -f ‘{{ .Mounts }}’ nginx

Docker Swarm requires more than one manager node to achieve fault tolerance12. A single manager node is not fault tolerant because if it goes down, the entire cluster goes down3. For a swarm to be fault-tolerant, it needs to have an odd number of manager nodes2. For example, a three-manager swarm tolerates a maximum loss of one manager2. Therefore, a configuration with one manager node for two worker nodes will not achieve fault tolerance for managers in a swarm12.

= The command ‘docker run --volume /data:/mydata:ro ubuntu’ will mount the host’s ‘/data’ directory to the ubuntu container in read-only mode. The --volume or -v option allows you to mount a host directory or a file to a container as a volume1. The syntax for this option is:

-v|--volume=[host-src:]container-dest[:]

The host-src can be an absolute path or a name value. The container-dest must be an absolute path. The options can be a comma-separated list of mount options, such as ro for read-only, rw for read-write, z or Z for SELinux labels, etc1. In this case, the host-src is /data, the container-dest is /mydata, and the option is ro, which means the container can only read the data from the volume, but not write to it2. This can be useful for sharing configuration files or other data that should not be modified by the container3. References:

• Use volumes | Docker Documentation
• Docker run reference | Docker Documentation
• Docker - Volumes - Tutorialspoint

The set of commands docker container inspect and docker port can identify the published port(s) for a container. The docker container inspect command returns low-level information about a container, including its network settings and port bindings1. The docker port command lists port mappings or a specific mapping for the container2. Both commands can show which host port is mapped to which container port, and the protocol used. For example, docker container inspect -f '{{.NetworkSettings.Ports}}' container_name will show the port bindings for the container_name3. Similarly, docker port container_name will show the port mappings for the container_name. References:

• docker container inspect
• docker port
• How to Expose and Publish Ports in Docker
• [How to obtain the published ports from within a docker container?]

The provided Kubernetes NetworkPolicy YAML configuration indicates that the policy applies to pods with the label tier: backend in the default namespace1. The ingress rule allows traffic from pods with the label tier: api1. Therefore, a request issued from a pod bearing only the tier: frontend label to a pod bearing the tier: backend label will be blocked by this networkPolicy1. This is because the networkPolicy does not have a rule allowing ingress from pods with the tier: frontend label1. For more information on Kubernetes NetworkPolicies, you can refer to the Kubernetes Documentation on Network Policies.

= The command docker inspect nodes will not list all nodes in a swarm cluster from the command line. This command is invalid, as docker inspect requires one or more object names or IDs as arguments1. To list all nodes in a swarm cluster, you need to use the docker node ls command from a manager node2. This command will display the ID, hostname, status, availability, manager status, and engine version of each node in the swarm2. You can also use the -f or --filter flag to filter the nodes by various criteria, such as role, label, or name2. References:

• 1: docker inspect | Docker Docs
• 2: docker node ls | Docker Docs

 Namespaces are a Linux kernel feature that isolate containers from each other and from the host system. They limit the access of a container to host resources, such as CPU or memory, by creating a separate namespace for each aspect of a container, such as process IDs, network interfaces, user IDs, etc. This way, a container can only see and use the resources that belong to its own namespace, and not those of other containers or the host12. References:

• Isolate containers with a user namespace | Docker Docs
• Docker overview | Docker Docs

n: = Using the DTR web UI to make all tags in the repository immutable is not a good way to prevent an image, such as ‘nginx:latest’, from being overwritten by another user with push access to the repository. This is because making all tags immutable would prevent any updates to the images in the repository, which may not be desirable for some use cases. For example, if a user wants to push a new version of ‘nginx:latest’ with a security patch, they would not be able to do so if the tag is immutable. A better way to prevent an image from being overwritten by another user is to use the DTR web UI to create a promotion policy that restricts who can push to a specific tag or repository1. Alternatively, the user can also use the DTR API to create a webhook that triggers a custom action when an image is pushed to a repository2. References:

• Prevent tags from being overwritten | Docker Docs
• Create webhooks | Docker Docs

The action will not upgrade Docker Engine CE to Docker Engine EE. Disabling the Docker service via chkconfig or systemctl will only stop the Docker daemon from running, but it will not change the version or edition of the Docker engine1. To upgrade Docker Engine CE to Docker Engine EE, you need to follow these steps2:

• Download your Docker Enterprise license from the Docker Store).
• Install the docker-ee package from the Docker repository.
• Restart the Docker service and verify the version and edition. References: Start or stop the Docker daemon), How to upgrade Docker 18.09 Community Edition to Docker Enterprise 18.09)

= 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

 Control Groups (cgroups) are a Linux kernel feature that allow you to limit, modify, or allocate resources as needed1. Docker uses cgroups to isolate the resources used by containers, such as CPU, memory, disk I/O, network, etc2. This means that each container can have its own set of resource limits and constraints, and that the containers cannot interfere with each other or with the host system2. This improves the security, performance, and reliability of the containers and the system as a whole. References:

• Lab: Control Groups (cgroups) | dockerlabs
• Docker run reference | Docker Docs

 The command ‘kubectl get pods --all-namespaces -I env=development’ does not display all the pods in the cluster that are labeled as ‘env: development’. The reason is that the flag -I is not a valid option for kubectl get pods. The correct flag to use is --selector or -l, which allows you to filter pods by labels1. Labels are key-value pairs that can be attached to Kubernetes objects to identify, group, or select them2. For example, to label a pod with env=development, one can run:

kubectl label pods my-pod env=development

To display all the pods that have the label env=development, one can run:

kubectl get pods --selector env=development

or

kubectl get pods -l env=development

The --all-namespaces flag can be used to list pods across all namespaces3. Therefore, the correct command to display all the pods in the cluster that are labeled as ‘env: development’ is:

kubectl get pods --all-namespaces --selector env=development

or

kubectl get pods --all-namespaces -l env=development References:

• kubectl Cheat Sheet | Kubernetes
• Labels and Selectors | Kubernetes
• kubectl get | Kubernetes

To configure a Docker container to export container logs to a logging solution such as Splunk, you need to set the log-driver and log-opt keys to values for the logging solution in the daemon.json file. This will enable the Splunk logging driver, which sends container logs to HTTP Event Collector in Splunk Enterprise and Splunk Cloud1. You can also use the command-line flags --log-driver and --log-opt with docker run to use the Splunk driver for a specific container1. References:

• Splunk logging driver | Docker Docs
• Collecting docker logs and stats with Splunk | Splunk
• How to send Docker containers logs to Splunk?
• Splunk Logging Driver for Docker | Splunk

= A Dockerfile does not store persistent data between deployments of a container. A Dockerfile is a text document that contains instructions for building a Docker image. A Docker image is a read-only template that defines the layers and configuration of a container. A Docker container is an isolated and ephemeral instance of a Docker image that runs on the Docker Engine. Docker containers are not meant to store persistent data, as any changes made to the container’s filesystem are lost when the container is removed. To store persistent data between deployments of a container, you need to use volumes or bind mounts. Volumes and bind mounts are ways to attach external storage to a container, so that the data is preserved even if the container is deleted. Volumes are managed by Docker and stored in a location on the host system that is independent of the container’s lifecycle. Bind mounts are files or directories on the host system that are mounted into a container. References:

• Persist container data
• Dockerfile reference
• Docker MySQL Persistence
• Persist the DB
• Docker - Dockerfile, persist data with VOLUME

 = The command kubectl get pods --all-namespaces -label env=development is not valid because it has a syntax error. The correct syntax for listing pods with a specific label is kubectl get pods --all-namespaces --selector label=value or kubectl get pods --all-namespaces -l label=value. The error in the command is:

• The option flag for specifying the label selector is --selector or -l, not -label. For example, -label env=development should be --selector env=development or -l env=development.

The correct command for listing all the pods in the cluster that are labeled as env: development is:

kubectl get pods --all-namespaces --selector env=development

This command will display the name, status, restarts, and age of the pods that have the label env: development in all namespaces.

References: : Labels | Kube by Example : kubectl Cheat Sheet | Kubernetes

 = The correct command to list all nodes in a swarm cluster from the command line is docker node ls, not docker swarm nodes. The docker node command allows you to manage nodes in a swarm, such as listing, inspecting, updating, or removing nodes1. The docker swarm command allows you to manage the swarm itself, such as initializing, joining, leaving, or updating the swarm2. References:

• Manage nodes in a swarm | Docker Docs
• Manage a swarm | Docker Docs

While removing push access from all other users can prevent an image from being overwritten, it’s not the only way and might not be the most efficient or practical solution, especially in a collaborative environment. Docker Trusted Registry (DTR) provides a feature called ‘Immutable Tags’ which can be used to prevent an image, such as ‘nginx:latest’, from being overwritten. Once a tag is marked as immutable, DTR will prevent any user from pushing the same tag to the repository, thus preserving the image. This allows for better version control and prevents accidental overwrites. Therefore, the solution to prevent an image from being overwritten is not just to remove push access from all other users, but to use the features provided by DTR like ‘Immutable Tags’.