免密登陆

无密钥配置

（1）免密登录原理，如图所示

（2）生成公钥和私钥：

[root@hadoop003 .ssh]# 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:Ok8kToCeyjo30iYnrfUMMBbThPt4hgcMROobewzvgE4 root@hadoop003
The key's randomart image is:
+---[RSA 2048]----+
|oo..             |
|o.o.             |
|+oo..            |
|.=o. .           |
|o=B   o S        |
|+*B= o +         |
|oE*+  + .        |
|O.@+   +         |
|o@ oo   .        |
+----[SHA256]-----+
[root@hadoop003 .ssh]#

然后敲（三个回车），就会生成两个文件id_rsa（私钥）、id_rsa.pub（公钥）

（3）将公钥拷贝到要免密登录的目标机器上

[root@hadoop003 .ssh]# ssh-copy-id hadoop002
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/root/.ssh/id_rsa.pub"
The authenticity of host 'hadoop002 (47.111.251.254)' can't be established.
ECDSA key fingerprint is SHA256:YNsodxgiTBhRi6BaO1LqQrkOeudAVMaRisZJQdaJdAA.
ECDSA key fingerprint is MD5:b5:82:88:93:92:6a:01:ed:4d:6f:80:bc:68:1a:e8:c9.
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@hadoop002's password:

Number of key(s) added: 1

Now try logging into the machine, with:   "ssh 'hadoop002'"
and check to make sure that only the key(s) you wanted were added.

[root@hadoop003 .ssh]# ssh-copy-id hadoop003
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/root/.ssh/id_rsa.pub"
The authenticity of host 'hadoop003 (172.16.123.556)' can't be established.
ECDSA key fingerprint is SHA256:YKGJjhv5Q/fneno2xR5HWQjFBkeZL09SF4RwtWI8tC4.
ECDSA key fingerprint is MD5:30:ad:2b:59:1c:a8:37:d3:bf:69:6b:7d:8f:ee:3b:b8.
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@hadoop003's password:

Number of key(s) added: 1

Now try logging into the machine, with:   "ssh 'hadoop003'"
and check to make sure that only the key(s) you wanted were added.

[root@hadoop003 .ssh]# ssh-copy-id hadoop004
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/root/.ssh/id_rsa.pub"
^Z
[1]+  Stopped                 ssh-copy-id hadoop004
[root@hadoop003 .ssh]# vim /etc/hosts
[root@hadoop003 .ssh]# ssh-copy-id hadoop004
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/root/.ssh/id_rsa.pub"
The authenticity of host 'hadoop004 (47.110.91.340)' can't be established.
ECDSA key fingerprint is SHA256:y5y+JQhhdqAGOHgS9U7vvuqz0TrBjA6823skny8SYJE.
ECDSA key fingerprint is MD5:62:5b:a0:d7:08:ad:0d:97:44:35:5b:61:f4:1d:5f:f3.
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@hadoop004's password:

Number of key(s) added: 1

Now try logging into the machine, with:   "ssh 'hadoop004'"
and check to make sure that only the key(s) you wanted were added.

[root@hadoop003 .ssh]# ssh hadoop002
Last login: Wed Jan 15 00:11:57 2020 from 172.16.25.74

Welcome to Alibaba Cloud Elastic Compute Service !

[root@hadoop002 ~]#

.ssh文件夹下（~/.ssh）的文件功能解释

表2-4

known_hosts	记录ssh访问过计算机的公钥(public key)
id_rsa	生成的私钥
id_rsa.pub	生成的公钥
authorized_keys	存放授权过得无密登录服务器公钥

[root@hadoop003 .ssh]# ll
total 16
-rw------- 1 root root  792 Jan 15 00:16 authorized_keys
-rw------- 1 root root 1679 Jan 15 00:13 id_rsa
-rw-r--r-- 1 root root  396 Jan 15 00:13 id_rsa.pub
-rw-r--r-- 1 root root  557 Jan 15 00:16 known_hosts
[root@hadoop003 .ssh]#