The predefined users are specified in the membershipType field of the OrganizationConfig plugin parameter.

<field name="user">

  <collection type="java.util.ArrayList">

    <value>

      <object type="org.exoplatform.services.organization.OrganizationConfig$User">

        <field name="userName"><string>root</string></field>

        <field name="password"><string>exo</string></field>

        <field name="firstName"><string>root</string></field>

        <field name="lastName"><string>root</string></field>

        <field name="email"><string>exoadmin@localhost</string></field>

        <field name="groups"><string>member:/admin,member:/user,owner:/portal/admin</string></field>

      </object>

    </value>

    <value>

      <object type="org.exoplatform.services.organization.OrganizationConfig$User">

        <field name="userName"><string>exo</string></field>

        <field name="password"><string>exo</string></field>

        <field name="firstName"><string>site</string></field>

        <field name="lastName"><string>site</string></field>

        <field name="email"><string>exo@localhost</string></field>

        <field name="groups"><string>member:/user</string></field>

      </object>

    </value>

    ...

  </collection>

</field>