Identity management

Identity management (IDM), sometimes also identity and access management (IAM), deals with how users gain a digital identity, the roles, and sometimes the permission granted to this identity.

Software

There is a number of software which helps doing identity management. Amongst, in alphabetical order, tools and related:

Google Authenticator, two-step authentication, using one time passwords.
Initiative for Open Authentication, standardization on how to get an access token for a web API call. Includes passwords, but will in future use WebAuthn.
kanidm, some info here. Successor of LDAP, Kerberos. Server side of WebAuthn.
Kerberos, with Active Directory integration, FreeIPA
LDAP authentication, passwords in a central server.
PAM, Linux pluggable authentication modules. Kerberos, LDAP, kanidm, etc. can be plugged into Linux.
Universal 2nd Factor, replaced by WebAuthn.
Users and groups. can be stored on a system or centrally via LDAP, kanidm.
WebAuthn, browser web authentication API, replacement for password authentication, backwards compatible with Universal 2nd Factor.