哪个命令会在 ~/.ssh/id_rsa 生成一个 2048 位的 RSA 密钥对，并使用空口令？
~/.ssh/id_rsa
ssh-keygen -t rsa -b 2048 -N ~/.ssh/id_rsa
ssh-keygen -t rsa -b 2048 -N "" -f ~/.ssh/authorized_keys
ssh-keygen -t rsa -b 2048 -N "" -f ~/.ssh/id_rsa
ssh -t rsa -b 2048 -N "" ~/.ssh/id_rsa