View Full Version : Windows NT PDC and BDC
August 29, 2003, 07:59 PM
Found myself in a situation today. I have a domain with a PDC and a BDC, replication worked fine. I had to take the PDC off-line and wipe the hard drive (due to persistent problems, Dr. Watson errors, security patches, Proprietary software requirements, etc) and reinstall the OS.
After installation I was confused as to what would happen, would the PDC synchronize with the BDC - meaning would it get the the info from that the BDC has or, would it overwrite the BDC.
I tried to promote the BDC to PDC while the the original PDC was up, however it wouldn't happened - not sure why not.
My question is, what is the rule of thumb in a situation like this? Is this an unusual situation - talking about the promotion of the BDC?
August 29, 2003, 08:13 PM
The BDC cannot be promoted to a PDC while the original PDC is up.This will cause a Browser election to be effected between the two.You should configure the old PDC as a BDC (demote) then promote the old BDC to a PDC. After this is done synchronize the domain. This will copy the SAM database in the newly promoted PDC to the BDC. You would then demote the PDC and then promote the BDC.
If you do not do this and the domain is synchronized then the stored SAM database (in the BDC) with the usernames and computer accounts from the PDC which you re-installed will be over-written..
August 29, 2003, 08:22 PM
I is the BDC which gets the information from the PDC. As my instructor from the Software Training Center would say, "The PDC is married to the BDC."
The BDC (Backup Domain Controller) gets a copy of the SAM database from the PDC (Primary Domain Controller). The synchronization is done automatically aftetr a specified time period.If thjis is of great concern to you I would reccomend demoting the PDC within User Manager For Domains then taking it offline then promoting the BDC to a PDC from within User Manager For Domains. If the two are then put on the network the correct SAM database will be retained after synchronization..
August 31, 2003, 09:51 AM
Sue taught you well. ;D She is quite good.
I would reccomend demoting the PDC within User Manager For Domains then taking it offline then promoting the BDC to a PDC from within User Manager For Domains.
The tool he needs is Server Manager. User Manager is used to manage user accounts.
Some of the documentation suggests promoting the BDC while the PDC is on-line. This forces the PDC and BDC to synchronize before the changes are made. The process will:
synchronize the PDC to BDC
demote the PDC
promote the BDC
I am not sure why the PDC is not responding in this case.
He could try another approach. Assume Adam is the PDC and Eve is the BDC. You said they were married. ;D
Synchronize the domain to make sure all changes to Adam's SAM have been replicated to Eve
Demote Adam to a BDC
Promote Eve to a PDC
Reload Windows on Adam and install it as a BDC
Synchronize the SAM database. Necessary if there has been a long delay since Adam became a BDC.
Demote Eve to a BDC
Promote Adam to a PDC
If there is a long delay after re-loading Adam as a BDC, you may want to synchronize the SAM. I would do the whole process in the evening when most users have gone home.
Take your time and ensure that each step completes properly before moving on to the next one.
August 31, 2003, 10:08 AM
Microsoft's knowledge base is quite good. Just do a search on the error message you are getting. Read up on the topic before doing the change over.
There may be issues with one of the machines that need to be resolved before you proceed.
After you demote Adam to a BDC and promote Eve to a PDC, take Adam off line and make sure you can add a user from Eve and change the user's password from a workstation. You want to verify that Eve is now a fully functional primary domain controller.
Just do proper checks like this after each step has been taken. Remember to delete the test users when you are finished.
September 1, 2003, 09:45 AM
The BDC was actually promoted to a PDC and we had also reinstalled the previous PDC as a PDC again. I guess it got worse. I found a solution at
http://www.ntfaq.com/Articles/Index.cfm?ArticleID=13525 however. It worked.
I also learnt that the Software IdealAdmin which we have in house also provide a solution. It has the functionality to copy users from one windows NT/2000/XP machine to another. I tried pulling the users from the NT 4.0 server onto a 2K Professional machine it works perfectly. The next thing would be to pull them from that 2k Pro box onto the old PDC. Synchronization would then follow.
September 1, 2003, 01:59 PM
Yes jamrock..Sue is good..I stand corrected. Server Manager is the correct utility..I think Weird_O wanted to know if the syncrhonization would overwrite the SAM on the Eve PC.He had already reinstalled NT 4 Server on the Adam PC.
September 1, 2003, 02:00 PM
That Ideal Admin is a cool tool Weird_O. I'll definitely check it out.
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