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Explanation
A physical machine participating in the swarm is a node in the context of a swarm mode cluster. A node is an instance of the Docker engine participating in the swarm. A node can be either a physical machine or a virtual machine. Nodes are either managers or workers. Managers maintain cluster state and manage cluster tasks.
Workers execute tasks assigned by managers. References:
https://docs.docker.com/engine/swarm/key-concepts/#nodes-and-services,
https://docs.docker.com/engine/swarm/how-swarm-mode-works/nodes/

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.

Explanation
x.500 is not a supported user authentication method for Universal Control Plane (UCP). x.500 is a series of standards for directory services that define how distributed directory information can be accessed and managed over a network. x.500 is not an external authentication backend that UCP supports. UCP supports LDAP, Active Directory, and SAML as external authentication backends. References:
https://docs.docker.com/ee/ucp/admin/configure/external-auth/, https://en.wikipedia.org/wiki/X.500

= 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. Reference: Docker Documentation, Runtime privilege and Linuxcapabilities, Change system date time in Docker containers without impacting host, Is it possible to change time dynamically in docker container?