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You configure a local Docker engine to enforce content trust by setting the environment variable
DOCKER_CONTENT_TRUST=1.
If myorg/myimage: 1.0 is unsigned, does Docker block this command?
Solution: docker image import
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 Notaryserver1. 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 <tarball>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.Reference:
Content trust in Docker
Automation with content trust
[docker image import]
[Content trust and image tags]
Will this Linux kernel facility limit a Docker container's access to host resources, such as CPU or memory?
Solution: namespaces
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.Reference:
Isolate containers with a user namespace | Docker Docs
Docker overview | Docker Docs
Seven managers are in a swarm cluster.
Is this how should they be distributed across three datacenters or availability zones?
Solution: 4-2-1
= This is not how the seven managers should be distributed across three datacenters or availability zones.A swarm cluster is a group of Docker hosts that are running in swarm mode and act as managers or workers1.A manager node is responsible for maintainingthe swarm state and orchestrating the services2.A swarm cluster needs a quorum of managers to operate, which means a majority of managers must be available and able to communicate with each other3.
The problem with distributing the seven managers as 4-2-1 is that it creates a split-brain scenario, where the cluster can lose the quorum if one datacenter or availability zone fails. For example, if the datacenter with four managers goes down, the remaining three managers will not have enough votes to form a quorum, and the cluster will stop functioning.Similarly, if the datacenter with one manager goes down, the cluster will lose the tie-breaking vote and will not be able to elect a leader4.
A better way to distribute the seven managers across three datacenters or availability zones is to use 3-2-2, which ensures that the cluster can tolerate the failure of any one datacenter or availability zone and still maintain the quorum. For example, if the datacenter with three managers goes down, the remaining four managers will have enough votes to form a quorum and elect a leader.Similarly, if the datacenter with two managers goes down, the remaining five managers will have enough votes to form a quorum and elect a leader4.Reference:
Swarm mode overview | Docker Docs
Administer and maintain a swarm of Docker Engines | Docker Docs
Raft consensus in swarm mode | Docker Docs
Docker Swarm: How to distribute managers across availability zones? - Stack Overflow
You want to create a container that is reachable from its host's network. Does this action accomplish this?
Solution:Use either EXPOSE or --publish to access the containers on the bridge network
The answer depends on whether you want to access the container from the host's network or from other containers on the same network. EXPOSE and --publish have different effects on the container's port visibility.Reference:Docker run reference,Dockerfile reference,Docker networking overview
Is this the purpose of Docker Content Trust?
Solution: Verify and encrypt Docker registry TLS.
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 server12. DCT does not verify or encrypt the Docker registry TLS, which is a separate mechanism for securing the communication between the Docker client and the registry server.The purpose of DCT is to ensure that the images are not tampered with or maliciously modified by anyone other than the original publisher3.Reference:
Content trust in Docker | Docker Docs
Docker Content Trust: What It Is and How It Secures Container Images
Automation with content trust | Docker Docs
