Rsync using SSH RSA auth key

How to rsync files between two servers when remote server uses an RSA key for authentication.

Format:
rsync $options $host:$from $to

rsync -avz -e "ssh -i key.rsa" \
user@domain.com:/var/www /var/www/backup

The ‘-avz’ options are used for creating archive, being verbose and compressing the file transfer.

‘-e “$command”‘ specifies the shell command to use; in this case calling the SSH RSA key used for authentication