# su - zimbra -c '/opt/zimbra/libexec/zmslapadd -c /srv/zimbra-ldap/ldap-config.bak'
slapadd: could not add entry dn="cn=config" (line=1):
_ 0.21% eta 35s elapsed none spd 24.2 k/s
I went directly but have the network (commerical) version. I had no issues at all and used the rsysnc method.
1) install centos 8
2) convert centos 8 to oracle 8 (which I will now call RHEL 8) via the script they provide
3) install zimbra software only on RHEL 8 (install.sh -s)
4) move /opt/zimbra out of the way on RHEL 8
5) copy /opt/zimbra from centos 6 except sparse files and backups to oracle 8 /opt/zimbra
6) install software only again (install.sh -s) on RHEL 8
7) put centos 6 ldap database file in place on RHEL 8. It's a sparse file so I used tar to create/extract.
8) install.sh to complete the update and fix anything
No issues at all.
Note: make sure that you are running the RHEL 8 slapadd and not the RHEL 6 version on your new host. That is why we do the second install.sh -s in step 6.