Question:
how can I debug slapd starting issues
Answer:
Start the slapd without systemd to get better/more starting information:
root@slave:~# SYSTEMCTL_SKIP_REDIRECT=1 bash -x /etc/init.d/slapd start
You can start slapd manually with
/usr/sbin/slapd -h "ldapi:/// ldap://:7389/ ldaps://:7636/" -d5
Without samba you may check also with
/usr/sbin/slapd -h ldapi:/// ldap://:7389/ ldap://:389/ ldaps://:7636/ ldaps://:636/