Cant add NAS as member DC

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Cant add NAS as member DC

Operating system
  1. Windows
Mobile operating system
  1. iOS
I am trying to add a DS1618+ as a Member DC in an existing Windows domain. It does all its checks fine, then starts and gets to about .5% complete, hangs for a bit, then fails. Not much in the way of an error message, it just says to "Failed to join domain. Contact Synology Support".

I SSH'd into the box and went to /var/log and found this in the "synoscgi.log"

failed to exec '/var/packages/SMBService/target/usr/bin/samba-tool domain join mydomain.local DC --dns-backend BIND9_DLZ --username myusername --password <masked> -configfile /etc/samba/synoadserver.conf', ret 255

task (DomainSDCConnector) execution failed because failed to create domain

I then looked in /etc/samba for the "synoadserver.conf" file referenced in the failed command. It did not exist. So, I searched the file system, found one, copied that to /etc/samba, tried to become a member DC again, it failed again the same way. Oddly, the file I copied into /etc/samba disappeared which leads me to believe that the NAS is responsible for creating this file and dropping it in that folder.

I should point out that I have no issue with simply joining the NAS to the same domain, I am just unable to make it a member DC.

Any ideas? What should I look for in the log dump via Support Center/Support Services/Generate Logs ?? The system is air gapped and has no internet access which further complicates issues.

Thanks in advance for any help you can provide.
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If memory serves me correct, windows server and synology nas cannot coexist as DC's. There is a lot of guides kicking atound on the 'other' synology forum and i know that one of them works as I setup a pair of DS1817+ in HA running a 30 user domain, which has been ticking along for just unsder 4 years with zero downtime. My employer bought a company in poland in 2017, which was joined to the former owners network in france and not only did i have to build the AD on synology from scratch, I couldn't put it into production until the other servers were removed from the local network. 99% sure it is one or the other.

Further to this, the Synology server can do evertything you would want from a windows server, just need to use non domain PC with RSAT installed (just has to be correct version to be compatible with ad server version)
Thanks for the help. I do have RSAT working as you state in another small domain, but in that domain, there is only Synology in the mix, no windows servers. The info I have been giving to Synology support seems to be way over their heads. So, I gathered the log files, unzipped the .DAT and dug into those files. In one of those log files there is this error: WERR_DS_INCOMPATIBLE_VERSION which would be right in line with what you are saying. You would think the first answer from Synology support would be "you cant become a member DC of a Windows domain". I will wait to see what they have to say, but for now, I will give up on this idea. Thanks again.
Finally, Synology support validated your answer. You can't mix Synology directory server with windows AD.
I'm glad you got your answer. I know synology AD can be a bit offputting / daunting but it does what it says on the tin. HA certainly has played it's role too - when it has had to work it has, with downtime of less than a minute every time.

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