一、准备三台虚拟机
| IP | 主机名 |
|---|---|
| 192.168.1.159 | server1 |
| 192.168.1.198 | server2 |
| 192.168.1.199 | server3 |
二、查看修改主机名
2.1 查看当前服务器的主机名
[root@localhost ~]# hostname
localhost.localdomain
修改主机名，再次查看主机名（hostname命令为临时修改、重启失效，永久修改需要编辑/etc/hostname文件）
[root@localhost ~]# hostname server1
[root@localhost ~]# hostname
server1
依次为server2、server3修改主机名
[root@localhost ~]# hostname server2
[root@localhost ~]# hostname
server2
[root@localhost ~]# hostname server3
[root@localhost ~]# hostname
server3
2.2 修改这3台机器的/etc/hosts文件
将IP与主机映射填入hosts文件（该IP地址是我虚拟机的IP，根据自己实际情况修改）
192.168.1.159 server1
192.168.1.198 server2
192.168.1.199 server3
修改前文件内容
127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4
::1 localhost localhost.localdomain localhost6 localhost6.localdomain6
修改后文件内容（保证三台主机改文件内容一致）
127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4
::1 localhost localhost.localdomain localhost6 localhost6.localdomain6
192.168.1.159 server1
192.168.1.198 server2
192.168.1.199 server3
验证主机名是否映射IP成功，直接ping主机名称，ping通就ok
ping server1
ping server2
ping server3
三、给3个机器生成秘钥文件
每台机器输入该命令
ssh-keygen -t rsa -P ''
按回车确定，/root目录下会生成一个id_rsa.pub秘钥文件（每台机器都会产生一个）
[root@localhost ~]# ll /root/.ssh/
-rw-------. 1 root root 1675 4月 24 17:02 id_rsa
-rw-r--r--. 1 root root 394 4月 24 17:02 id_rsa.pub
四、创建authorized_keys文件
每台机器创建一个authorized_keys文件
touch /root/.ssh/authorized_keys
接下来是将这三台服务器的id_rsa.pub内容复制到authorized_keys文件中
server1的id_rsa.pub内容
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQD4gNi3PuQybl3I7yZNISSB8KTmpsRs2oZ9sYqJCxMAVnUIFTtGzXQqJ8joG8gHj4t/QA5YwIYM3bW6WKky7L3wHWwqmutfCnSQIuttNE0r79fMV9JoEqMDyZu++9orIF6jfspe3h6sILSF8OrcMr0x03bpHmLc82AqeKsU5wcNZFnjzqAaJPPT71jxEgOJ5LxMvzxDAagsGnyHMIo9Be20xAgUID6W/gPpv+7AAKS6hflgqWqubgFerh/mNL0u4F17zter3ny6OHe8sugobDchOxHiNc+sxxgrwPPgOgkb3Wi3veAjHe7HJ3kDSOsaOhYkRW1aLU9F7oWDcGAtPVad root@server1
server2的id_rsa.pub内容
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQC+OOSahGWs6aAqEYtcqHiSwmvxHkYlLsiqpgcaoIMYkBxoE321q0uV2ZoWidWSnsuotX0kdwIxhS3/X29FkHOlVeViCdqCwMvkDfwugRVvQiMgfMnultkIEpGf91ARtCX2pCcFulXun0UOy7SOjZmKl7KZpPp3DGqftSR2ZpLiCdKAVIPMYuEQpWMbYGWwiWlwPRHvbsoJHGhFVuKlHoHSQ5uT4T+qz4kbOipJ9flTTSAGkHf4/wQyrOAO9Bw+1Hesr500r24JmFmuqwRzuXMFOki7d8wHiPSnM/thX2YuIAw0jogLVbD+UTa9pu0UhAKV3meEK4ljfRnqib/YOiIl root@server2
server3的id_rsa.pub内容
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQC69S37Fdx7TzOs0AMZmZn+/hUQuKBkYJye7sLsYfORnGAkLgtxov0aU6YgkpE1LARp5LKpi+xnf7aklnFdkmpauLU2lH+hWUd2py79d1fVYwvXrmNL2YKpJiAnlh3gTAgj61CWMAsp7tjiYpGgVSWR5wgFRoe7omxIi1c/JdsNujzfZEB2Eq7GgVOKc0+sro+/JNMR0Eh91iy9N64Xs7DAk2rpbO/TtRmRSTVVU8oc95Au/jIkaILp3XvsGjOyPsTCGHVuD+m2YTXawbVfyIntiNLYBT2Bm78mqyA9j0NbS2ihVJeOKdzys3mxh1yK94E7r3V1YmMlIVZSmp6yETrF root@server3
将这三条秘钥拼接起来放入authorized_keys（保证这三台机器的此文件内容一致，可以将文件直接复制过去，也可直接修改）
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQD4gNi3PuQybl3I7yZNISSB8KTmpsRs2oZ9sYqJCxMAVnUIFTtGzXQqJ8joG8gHj4t/QA5YwIYM3bW6WKky7L3wHWwqmutfCnSQIuttNE0r79fMV9JoEqMDyZu++9orIF6jfspe3h6sILSF8OrcMr0x03bpHmLc82AqeKsU5wcNZFnjzqAaJPPT71jxEgOJ5LxMvzxDAagsGnyHMIo9Be20xAgUID6W/gPpv+7AAKS6hflgqWqubgFerh/mNL0u4F17zter3ny6OHe8sugobDchOxHiNc+sxxgrwPPgOgkb3Wi3veAjHe7HJ3kDSOsaOhYkRW1aLU9F7oWDcGAtPVad root@server1
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQC+OOSahGWs6aAqEYtcqHiSwmvxHkYlLsiqpgcaoIMYkBxoE321q0uV2ZoWidWSnsuotX0kdwIxhS3/X29FkHOlVeViCdqCwMvkDfwugRVvQiMgfMnultkIEpGf91ARtCX2pCcFulXun0UOy7SOjZmKl7KZpPp3DGqftSR2ZpLiCdKAVIPMYuEQpWMbYGWwiWlwPRHvbsoJHGhFVuKlHoHSQ5uT4T+qz4kbOipJ9flTTSAGkHf4/wQyrOAO9Bw+1Hesr500r24JmFmuqwRzuXMFOki7d8wHiPSnM/thX2YuIAw0jogLVbD+UTa9pu0UhAKV3meEK4ljfRnqib/YOiIl root@server2
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQC69S37Fdx7TzOs0AMZmZn+/hUQuKBkYJye7sLsYfORnGAkLgtxov0aU6YgkpE1LARp5LKpi+xnf7aklnFdkmpauLU2lH+hWUd2py79d1fVYwvXrmNL2YKpJiAnlh3gTAgj61CWMAsp7tjiYpGgVSWR5wgFRoe7omxIi1c/JdsNujzfZEB2Eq7GgVOKc0+sro+/JNMR0Eh91iy9N64Xs7DAk2rpbO/TtRmRSTVVU8oc95Au/jIkaILp3XvsGjOyPsTCGHVuD+m2YTXawbVfyIntiNLYBT2Bm78mqyA9j0NbS2ihVJeOKdzys3mxh1yK94E7r3V1YmMlIVZSmp6yETrF root@server3
五、ssh免秘钥验证
在server1上输入命令
ssh server2
ssh server3
在server2上输入命令
ssh server1
ssh server3
在server3上输入命令
ssh server1
ssh server2
结果都应该一样，第一次输入yes后，就会免密码登录其他主机，按Ctrl+d或输入exit退出。
