Certificate and private key file on a Cisco ACS appliance is generated and get saved on the local HDD.
Certificate file—The certificate file that you want to generate. When you submit this page, ACS creates the certificate file by using the location and filename that you specify.
–ACS for Windows—Type the full directory path and name of the file; for example, c:\acs_server_cert\acs_server_cert.cer.
–ACS Solution engine—Type only the name of the file; for example, acs_server_cert.cer. You don't need to specify the location.
http://www.cisco.com/c/en/us/td/docs/net_mgmt/cisco_secure_access_control_server_for_windows/4-2-1/User_Guide/acs421ug/SCAuth.html#wp327500
Are you try to backup this private file, or trying to pull this file out of the appliance? If yes, then the Generate Self-Signed Certificate edit page also contains mandatory configuration fields that you use to specify the FTP server to which the certificate file and the corresponding private key file are transferred:
•FTP Server—The IP address or hostname of the FTP server where the certificate file and the corresponding private key file are to be transferred. If you specify a hostname, DNS must be enabled on your network and must be correctly configured on the serial console.
•Login—A valid username that enables ACS to access the FTP server.
Tip The Login box accepts domain-qualified usernames in the format DOMAIN\username, which may be required if you are using a Microsoft FTP server.
•Password—The password for the username provided in the Login box.
•Remote Directory—The directory to which you want to transfer the files. The directory must be specified relative to the FTP root directory.
Let me know if you've any further questions.
~BR
Jatin Katyal
**Do rate helpful posts**
~Jatin
