A default administrator user is predefined during the Redmine installation process. This administrator user has full and unrestricted control over all application features, including all other users. Default user is first to login.
In case of manual Redmine installation, default user is set as
User name: admin
Password: admin
It is strongly recommended to change this password at first login to improve default administrator security (Go to My account > Change password). Also, at first login Redmine may request the default user password to be changed.
In some cases of alternative to manual installation (e.g., using one of the third-party Redmine bundles), Setup allows a default administrator user to be defined manually with a different user name and password.