During the setup of a Master-Slave OpenLDAP environment we had to deal with a "strange" error log message on the slave server.
The server logged:
Jun 25 06:57:02 ldapsrv02 slapd: Entry (cn=vwxyz,dc=vwxyz,dc=xy): object class 'simpleSecurityObject' requires attribute 'userPassword'
In the first step of figuring out what is causing this issue we consulted Google and found a lot of articles/questions dealing with the same problem. But none of the results was providing the right hint to solve it.