Where is the proxy account stored on an NIS node?

Where is the proxy account stored on an NIS node?

I would like to know where the private key for the proxy account is stored on the filesystem of an NIS node (for the purposes of backup and restore).

Is is stored in ~/nem/nis/data ?

The following explanation of delegated harvesting seems to say that the proxy account is created and authorized by the NEM NCC wallet, and then sent to the specific NIS node to be used for harvesting:

The ‘magic’ behind delegated harvesting

Ok, you wanted to hear it:
If you activate delegated harvesting, NCC (NEM Community Client) initiates an “importance transfer” transaction that is processed on the blockchain. This creates a mapping for the importance score of the account to an empty “proxy” account (balance: 0 XEM). When the activation of delegated harvesting has completed and you start harvesting on a remote NIS, the private key of the “proxy” account is then passed to the remote NIS to sign generated blocks, but the fees you earn are still directly sent to the original account. With the private key of the “proxy” account it is not possible to transfer your importance score to any other account, and because it has a balance of zero, no funds can be stolen either. Isn’t that beautiful?

source: How Local and Delegated Harvesting Works

one additional question I have is: Do I need to run both NIS and NCC on the node to do delegated harvesting?