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Amazon Elastic Compute Cloud Developer Guide Miscellaneous By describing images (ec2dim) with the "-a" flag. This shows all AMIs to which you have access. The AMIs with product codes listed are paid AMIs. Example: run ec2dim -a, and the result contains an AMI with ID ami-bd9d78d4. This is our Demo Paid AMI with product code A79EC0DB. How can I determine if a public AMI is paid? By describing images (ec2dim). An AMI is a paid AMI if a product code is returned. Example: run ec2dim -a amazon, and the AMI ami-bd9d78d4 will be returned with a product code (A79EC0DB). Is there anything that prevents a paid AMI from being rebundled? How can this be restricted? Paid AMIs are comparable to shared AMIs with regards to rebundling and trying to restrict rebundling. If you allow a user running the AMI to see all of its contents, the user could rebundle these into their own AMI. For more information, review the following sections of this guide: Building Shared AMIs, Sharing AMIs, Using Shared AMIs. Why can't I query a particular AMI's attributes to see if the AMI is paid? Only the owner of an AMI can query the AMI attributes. However, anyone can tell if an AMI is paid by describing images (ec2dim). An AMI is paid if a product code is returned. Example: run ec2dim -a amazon, and the AMI with ID ami-bd9d78d4 will be returned with a product code (A79EC0DB). Who can use the confirm-product-instance command? Only the owner of the AMI can use this command. Owners use this command with supported AMIs to determine if a supported instance with a given product code attached is up and running. Miscellaneous Are there any special requirements to use FTP? The File Transfer Protocol (FTP) has a PORT command by which a client sends its address back to the server. The server then connects to the client at that address to send the file data. If the client looks up its own internal address and sends this to the server, the connection will fail. In this specific case, there are two solutions to the problem. First, the implementation of NAT that EC2 uses recognizes FTP as a special case and rewrites the PORT command address (if the ftp client connects to the server on the standard port). Second, the client can use "passive FTP" which makes connections only to the server, rather than from the server to the client. In general, applications which encode local addresses and port numbers in data sent to external servers may have problems with NAT. Care must always be taken to send the public address, rather than the internal one. API Version 2007-03-01 155