backupwallet "destination"
Safely copies wallet.dat to destination, which can be a directory or a path with filename.
Arguments:
1. "destination" (string) The destination directory or file
Examples:
> bitcoin-cli backupwallet "backup.dat"
> curl --user myusername --data-binary '{"jsonrpc": "1.0", "id":"curltest", "method": "backupwallet", "params": ["backup.dat"] }' -H 'content-type: text/plain;' http://127.0.0.1:8332/