Today when I after installing the active directory on my SharePoint box, I found that all of a sudden my Central Administration site stopped working. And keep on giving error message
Error: Service Unavailable HTTP Error 503. The service is unavailable.
In IIS console I noticed that App Pool for the central administration site was stopped. I restarted it, but again when I tried to open the site. App pool stopped again. And this happen again and again. After spending some time. I realized that because I installed active directory, I need to refresh credentials attached to App pool.
To change the identity account attached to app pool, select app pool and right click on it. Select the ‘Advanced Settings’.
One thing to notice is that previously if you defined the user like servername\administrator, then it won’t work now. If you use this way it will give message that username doesn’t exist. Because now you have set up the Active Directory.
Just use administrator and password and it will work or use domain/username and password.
I hope it will help.