It is a network server that is responsible for allowing host access to domain resources.
However, non-Windows domain controllers can be established via identity management software such as Samba and Red Hat FreeIPA.
The software and operating system used to run a domain controller usually consists of several key components shared across platforms.
[4] Other components, such as a public key infrastructure (Active Directory Certificate Services, DogTag, OpenSSL) service and Domain Name System (Windows DNS or BIND) may also be included on the same server or on another domain-joined server.
[5] Domain controllers are typically deployed as a cluster to ensure high-availability and maximize reliability.