Windows Tip Sheet

Automate Conversion of Your DCs Into GCs

Speed up DC deployment with a simple GC script.

I was recently helping a client deploy domain controllers (DCs) in about three dozen new offices (frequent flier miles, here I come). Because each office would eventually house about six hundred employees and because the company uses Exchange Server 2003, it seemed sensible to add two or three domain controllers to each office and ensure at least one of them was a Global Catalog (GC) server. To save time—we’re talking a total of 75 new DCs—we worked up an automated installations script to install the domain controllers.


After deploying DCs in two offices, we realized that none of the DCs we were installing had been made into GC servers. Of course, we realized this because users were going across the WAN for address book lookups and were raising heck about the poor performance of their e-mail clients! We quickly designated a GC in each location but wanted to fix the problem in our deployment technique.

We were using a Dcpromo answer file to handle the domain controller promotion process, and a little research turned up the answer: We simply needed to add the line ConfirmGC = Yes to the answer file for the DCs that would be GC servers. Seemed like a nice simple tip for speeding up DC deployment, so I thought I’d share it!

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More Resources:

  • Read more about automating DCpromo here.
  • Learn to combine unattended Setup and unattended DCpromo here.
  • The official word on the subject of unattended DC promotion can be found here.

About the Author

Don Jones has more than a decade of professional experience in the IT industry. He's the author of more than 30 IT books, including Windows PowerShell: TFM; VBScript, WMI, and ADSI Unleashed; Managing Windows with VBScript and WMI; and many more. He's a top-rated and in-demand speaker at conferences such as Microsoft TechEd and TechMentor, and writes the monthly Windows PowerShell column for Microsoft TechNet Magazine. Don is a multiple-year recipient of Microsoft's Most Valuable Professional (MVP) Award with a specialization in Windows PowerShell. Don's broad IT experience includes work in the financial, telecommunications, software, manufacturing, consulting, training, and retail industries and he's one of the rare IT professionals who can not only "cross the line" between administration and software development, but also between IT workers and IT management.

Reader Comments:

Wed, Jan 12, 2005 Anonymous Anonymous

No answer about scripting a change of DC to GC AFTER deployment?

Wed, Jan 5, 2005 Ron Kansas City

What if you want to make DCs into GCs after deployment? Any easy way to script this change?

Wed, Jan 5, 2005 Jim NJ

Thankyou for the reminder. MS pointed this out to all of us in AD Domains 101 back then. Most of us saw it and ignored it as we were still recovering from NT 4.0.

It seems that only those with experience building large corporate Exchange networks get this as it's impact is most notable with the address book.

I'll remeber this on the next deployment and save the headache of conversion.

PS - another good reason for an appliance. 600 users could run on a very small blade server as the info gets cached to the working DC from the GC.

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