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= A persistentVolumeClaim (PVC) is a request for storage by a user. It is similar to a Pod. Pods consume node resources and PVCs consume PV resources1. A PVC can specify a storage class, which is a way of requesting a certain quality of service for the volume2. If the storage class is empty, it means the PVC does not have any specific storage class requirements and can be bound to any PV that satisfies its size and access mode3. However, if there is no existing PV that matches the PVC’s requirements, the PVC remains unbound until a suitable PV becomes available. This can happen either by manual provisioning by an administrator or by dynamic provisioning using StorageClasses1. References:

Persistent Volumes | Kubernetes

Storage Classes | Kubernetes

Configure a Pod to Use a PersistentVolume for Storage | Kubernetes

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.

A Dockerfile is a text file that contains all the commands a user could run on the command line to create an image1. A Dockerfile is composed of instructions that specify the parent image, the packages to install, the files to copy, the ports to expose, and the commands to run2. A Dockerfile can be used to build a Docker image with the docker build command3. References:

Dockerfile reference | Docker Docs

What is a Dockerfile? A Step-by-Step Guide [2023 Updated] - Simplilearn

How to Build Docker Images with Dockerfile | Linuxize

Node taints are a way to mark nodes in a Swarm cluster so that they can repel or attract certain containers based on their tolerations. By applying node taints to the nodes that are designated for development or production, the company can ensure that only the containers that have the matching tolerations can be scheduled on those nodes. This way, the security policy requirements can be met. Node taints are expressed as key=value:effect, where the effect can be NoSchedule, PreferNoSchedule, or NoExecute. For example, to taint a node for development only, one can run:

kubectl taint nodes node1 env=dev:NoSchedule

This means that no container will be able to schedule onto node1 unless it has a toleration for the taint env=dev:NoSchedule. To add a toleration to a container, one can specify it in the PodSpec. For example:

tolerations:

- key: "env"

operator: "Equal"

value: "dev"

effect: "NoSchedule"

This toleration matches the taint on node1 and allows the container to be scheduled on it. References:

Taints and Tolerations | Kubernetes

Update the taints on one or more nodes in Kubernetes

A Complete Guide to Kubernetes Taints & Tolerations

= Creating images that contain the specific configuration for every environment is not a way to provision configuration to containers at runtime. This approach violates the principle of separating application code from configuration, and makes the images less portable and reusable across different environments1. It also increases the maintenance overhead and the risk of configuration drift, as any change in the configuration would require rebuilding and redeploying the images2. To provision configuration to containers at runtime, you should use a different mechanism, such as environment variables, command-line arguments, or config maps345. References:

Configuration management with Containers | Kubernetes

Environment variables in Compose | Docker Docs

Override the default command | Docker Docs

Configuration management with Containers | Kubernetes

= 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 …

Creating one pod and adding all the resources needed for each application is not a good way to accomplish the goal of grouping Kubernetes-specific resources for each application. This is because pods are the smallest unit of a Kubernetes application, and they are designed to run a single container or a set of tightly coupled containers that share the same network and storage resources1. Pods are ephemeral and can be created and destroyed by the Kubernetes system at any time. Therefore, putting multiple applications in one pod would make them harder to manage, scale, and update independently. A better way to accomplish the goal is to use namespaces, which are logical clusters within a physical cluster that can isolate resources, policies, and configurationsfor different applications2. Namespaces can also help organize secrets, which are Kubernetes objects that store sensitive information such as passwords, tokens, and keys3. References:

Pods | Kubernetes

Namespaces | Kubernetes

Secrets | Kubernetes

= Seccomp is a Linux kernel feature that allows you to restrict the actions available within the container. By using a seccomp profile, you can limit the system calls that a container can make, thus enhancing its security and isolation. Docker has a default seccomp profile that blocks some potentially dangerous system calls, such as mount, reboot, or ptrace. You can also pass a custom seccomp profile for a container using the --security-opt option. Seccomp can limit a container’s access to host resources, such as CPU or memory, by blocking or filtering system calls that affect those resources, such as setpriority, sched_setaffinity, or mlock. References:

Seccomp security profiles for Docker

Hardening Docker Container Using Seccomp Security Profile

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’.