On 3/28/19 7:46 PM, Gao wrote:
I am relatively new to openldap and I am having an issue when I try to setup Master-Slave replication. [..] Mar 28 11:40:39 test-ldap slapd[3438]: @(#) $OpenLDAP: slapd 2.4.40 (Nov 6 2016 01:21:28) $ mockbuild@worker1.bsys.centos.org:/builddir/build/BUILD/openldap-2.4.40/openldap-2.4.40
This is your main issue: You're using CentOS packages of a very old OpenLDAP version. 2.4.40 was released 2014-09-20 and many fixes were made since then. Also Red Hat added custom back-port patches so no-one here will be able to help you with that.
Before trying anything else please upgrade.
If you don't want to compile yourself the LDAP Toolbox project provides packages for RHEL/CentOS compiled from plain OpenLDAP upstream release:
https://ltb-project.org/documentation/openldap-rpm#yum_repository
It's also my personal opinion that it's much easier for beginners to start with static config (aka slapd.conf). You can convert that later to dynamic config (aka cn=config) but not vice versa.
Ciao, Michael.