Explanation
Signing and verifying image tags is the purpose of Docker Content Trust. Docker Content Trust (DCT) is a feature that allows you to use digital signatures for data sent to and received from remote Docker registries.
These signatures allow client-side or runtime verification of the integrity and publisher of specific image tags.
With DCT, image publishers can sign their images and image consumers can ensure that the images they pull are signed. References: https://docs.docker.com/engine/security/trust/

= Provisioning a Docker config object for each environment is a way to provision configuration to containers at runtime. Docker configs allow services to adapt their behaviour without the need to rebuild a Docker image.
Services can only access configs when explicitly granted by a configs attribute within the services top-level element. As with volumes, configs are mounted as files into a service's container's filesystem1. Docker configs are supported on both Linux and Windows services2. References: Docker Documentation, Configs top-level element

Explanation
This is how they should be distributed across three datacenters or availability zones, because having an even distribution of managers across datacenters or availability zones ensures that the swarm can survive the loss of any one datacenter or availability zone and maintain quorum. According to the official documentation, managers should be distributed evenly across datacenters or availability zones to ensure that the swarm can survive the loss of any one datacenter or availability zone.
References: https://docs.docker.com/engine/swarm/admin_guide/#add-manager-nodes-for-fault-tolerance

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

Explanation
= Linux capabilities are a way of restricting the privileges of a process or a container. By default, Docker containers run with a reduced set of capabilities, which means they cannot perform certain operations that require higher privileges, such as setting the system time1. To allow a container to set the system time, you need to grant it the SYS_TIME capability by using the --cap-add option when running the container2. For example, docker run --cap-add SYS_TIME alpine date -s 12:00 would set the system time to 12:00 inside the alpine container3. References: Docker Documentation, Runtime privilege and Linux capabilities, Change system date time in Docker containers without impacting host, Is it possible to change time dynamically in docker container?