ssh-keygen -t rsa
[root@aliyunrg ~]# ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa): 
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /root/.ssh/id_rsa.
Your public key has been saved in /root/.ssh/id_rsa.pub.
The key fingerprint is:
SHA256:onJuSYVI4CKNLgFphRWorCCglpoDnQJsuyj3NdF0VIE root@aliyunrg
The key's randomart image is:
+---[RSA 2048]----+
|+o=+.    ..oo.   |
|*O.     . E      |
|&++o . o .       |
|@*+ . o .        |
|X+.  ...S        |
|O.. ..o.         |
|.o.ooo .         |
|   ++            |
|   ..            |
+----[SHA256]-----+
[root@aliyunrg ~]#