ssh 公钥无法免密登陆远程服务器或者登陆需要密码

问题排查

权限问题

chmod 700 /home/skyler/.ssh
chmod 600 /home/skyler/.ssh/authorized_keys

端口安全问题

可能PAM安全控制的原因导致uid<1000的用户禁止登陆（非root用户），通过tail /var/log/secure -n 20查看发现以下提示

pam_succeed_if(sshd:auth): requirement "uid >= 1000" not met by user "root"

修改登陆用户的uid,usermod -u 端口号 用户名
修改登陆用户的gid,usermod -g 端口号 用户组

!!!注意

# 如果该用户已经有文件，需要批量修改文件的uid和gid
find / -user 用户端口号 -exec chown -h foo {} \;
find / -group 用户组端口号 -exec chgrp -h foo {} \;

好像可以通过修改/etc/ssh/sshd_config的UsePAM yes为UsePAM no解决，但是不建议这么做，降低了服务器安全性

密钥生成强度问题

未证实，但是如果还是登陆不上，可以尝试

ssh-keygen -b 4096 -t rsa

然后不停回车，输出如下

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:
............
The key's randomart image is:
+--[ RSA 4096]----+
|      .          |
|     o = . .     |
|      B = + E    |
|       @ + o     |
|      . S .      |
|       * =       |
|        = o      |
|         .       |
|                 |
+-----------------+

拷贝公钥到远程服务器

ssh-copy-id '-p ssh端口号 root@远程服务器IP地址'

输入root密码

[email protected]'s password: 
Now try logging into the machine, with "ssh ...", and check in:

  .ssh/authorized_keys

to make sure we haven\'t added extra keys that you weren't expecting.

尝试登陆

ssh root@远程服务器IP地址 -p ssh端口号