Ubuntu

ssh-copy-id riguz@10.226.21.75
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/Users/riguz/.ssh/id_ed25519.pub"
/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
riguz@10.226.21.75's password:

Number of key(s) added:        1

Now try logging into the machine, with:   "ssh 'riguz@10.226.21.75'"
and check to make sure that only the key(s) you wanted were added.

生成秘钥

首先生成秘钥，秘钥短语可以不生成。

ssh-keygen -t rsa
cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys

然后修改文件权限：

chmod go-w $HOME $HOME/.ssh
chmod 600 $HOME/.ssh/authorized_keys
chown `whoami` $HOME/.ssh/authorized_keys

修改sshd配置

vi /etc/ssh/sshd_config

RSAAuthentication yes
StrictModes yes
PubkeyAuthentication yes
AuthorizedKeysFile .ssh/authorized_keys

然后重启sshd服务:

service sshd restart
#centos 7:
systemctl restart sshd.service

然后就可以使用秘钥登陆了，把私钥(id_rsa)下载到本机登陆。注意权限的问题，另外，使用xshell登录的时候，还是要输用户名噢！（竟然犯了这么蠢的错误，还一直以为是权限的问题）