ssh问题

ssh 登录慢

ssh远程连接服务器及其缓慢，重启重装sshd无济于事

用ssh -vvv  发登录慢是卡在下面这步：

debug1: Entering interactive session.

后发现在执行机上systemd-logind导致cpu 100%的问题，使得登录异常缓慢，并且消耗资源。

原因
systemd-logind主要功能是为每一个登陆session创建一个systemd角度的cgroup管理对象，更方便对session使用cgroup，在实际场景中没有什么用处，关闭不会影响正常ssh登陆
在有crond任务时，触发systemd-logind回收不及时的bug
解决办法
关闭或重启systemd-logind

systemctl stop systemd-logind

ssh取消超时断开

 编辑/etc/ssh/sshd_config

ClientAliveInterval 60
ClientAliveCountMax 3

编辑/etc/profile

添加 TMOUT=0

为0就是设置不超时

免密登录

[root@master ~]# ssh-keygen -t rsa  #生成密钥，连续三个回车即可，除非想二次认证，就是使用ssh免密登录时再用密码认证
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa): 
Created directory '/root/.ssh'.
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:
10:a2:a8:c6:01:f4:21:94:2e:f7:e3:d5:17:4e:a7:53 root@master
The key's randomart image is:
+--[ RSA 2048]----+
|++... .          |
|.oo... .         |
|o...  .          |
|+.o    .  o E    |
|o+ .   .So =     |
|.   o . . =      |
|   . o   . .     |
|    .            |
|                 |
+-----------------+

[root@master ~]# scp .ssh/id_rsa.pub root@192.168.92.130:/root/.ssh/authorized_keys #将生成的id_rsa.pub传到 B服务器下
The authenticity of host '192.168.92.130 (192.168.92.130)' can't be established.
ECDSA key fingerprint is fe:45:19:51:dc:97:92:55:5e:5f:28:cd:b1:28:59:08.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '192.168.92.130' (ECDSA) to the list of known hosts.
root@192.168.92.130's password: 
Permission denied, please try again.
root@192.168.92.130's password: 
id_rsa.pub                                                                                                     100%  393     0.4KB/s   00:00    
[root@master ~]# ssh 192.168.92.130   #登录测试，发现已经能直接连接
Last failed login: Thu Mar 26 23:30:22 PDT 2020 from 192.168.92.128 on ssh:notty
There was 1 failed login attempt since the last successful login.
Last login: Thu Mar 26 22:54:46 2020 from 192.168.92.1
[root@slave-02 ~]#