linux中ssh免密通信的实现

[root@www ~]# ssh-keygen -t rsa -P \'\' 
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa): 
/root/.ssh/id_rsa already exists.
Overwrite (y/n)?

[root@www ~]#ssh-copy-id -i .ssh/id_rsa.pub root@172.16.75.1
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: \".ssh/id_rsa.pub\"
The authenticity of host \'172.16.75.1 (172.16.75.1)\' can\'t be established.
ECDSA key fingerprint is SHA256:YXhbTS9MfK2IQC4gtOW4RL8voHvFqC1cAAMJXuF3Wec.
ECDSA key fingerprint is MD5:2c:c0:94:e8:3a:e4:74:88:c0:d8:e0:01:20:81:1d:8e.
Are you sure you want to continue connecting (yes/no)? yes
/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
/usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
root@172.16.75.1\'s password: 
Number of key(s) added: 1
Now try logging into the machine, with:  \"ssh \'root@172.16.75.1\'\"
and check to make sure that only the key(s) you wanted were added.