If you have to join a Linux server to a Windows domain managed by Active Directory and add this server into a defined OU, here is what you have to type : (Supposing your Samba version is later than 3.0.23)
root@your_server:# net ads join -U admin_account@YOUR_COMPANY.ORG createcomputer=”/Computers/Servers/Your_office”
following this : “OU=Your_office,OU=Servers,OU=Computers,DC=YOUR_COMPANY,DC=ORG”
where admin_account is the login name of a Windows administrator part of the “YOUR_COMPANY.ORG” domain with enough privileges. Pay attention to createcomputer option and its syntax.