在docker中开启sshd操作

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2021年10月13日22:26:22在docker中开启sshd操作已关闭评论 18 3858字阅读12分51秒

首先在docker中安装openssh-server,安装完毕后切换到openssh-server的安装目录/etc/ssh下面。

运行ssh-keygen生成对应的密钥。

先看看sshd的配置文件sshd_config,里面有如下内容:

HostKey /etc/ssh/ssh_host_rsa_key
#HostKey /etc/ssh/ssh_host_dsa_key
HostKey /etc/ssh/ssh_host_ecdsa_key
HostKey /etc/ssh/ssh_host_ed25519_key

有rsa,dsa,ecdsa,ed25519的加密方式,根据这几种加密方式来生成对应的密钥对。

[root@655f62a4ed82 ssh]# ssh-keygen -t rsa //生成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:
0e:fa:07:36:bb:87:c1:60:14:be:41:41:01:1b:4b:bc root@655f62a4ed82
The key's randomart image is:
+--[ RSA 2048]----+
| .+o*+      |
| ..*.      |
| ooo      |
| E oo      |
|  ..o. S    |
|   .*o     |
|  .. *.    |
|   .o o    |
|   o+     |
+-----------------+
[root@655f62a4ed82 ssh]# ssh-keygen -t dsa //生成dsa
Generating public/private dsa key pair.
Enter file in which to save the key (/root/.ssh/id_dsa): 
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /root/.ssh/id_dsa.
Your public key has been saved in /root/.ssh/id_dsa.pub.
The key fingerprint is:
ee:8c:db:a8:24:68:0d:33:79:eb:09:33:ed:74:c3:66 root@655f62a4ed82
The key's randomart image is:
+--[ DSA 1024]----+
|         |
|         |
|         |
| .       |
| = .  S    |
| .B o .     |
|.=.=.E .    |
|. Bo= .*     |
|  +..+.+    |
+-----------------+
[root@655f62a4ed82 ssh]# ssh-keygen -t ecdsa //生成ecdsa
Generating public/private ecdsa key pair.
Enter file in which to save the key (/root/.ssh/id_ecdsa): 
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /root/.ssh/id_ecdsa.
Your public key has been saved in /root/.ssh/id_ecdsa.pub.
The key fingerprint is:
84:74:de:d1:e4:98:a1:5c:27:25:8e:b7:d6:27:fd:c9 root@655f62a4ed82
The key's randomart image is:
+--[ECDSA 256]---+
|   . . *++  |
|   . = * X.  |
|   . * * .  |
|    . . o .  |
|    S o o o |
|     .  o...|
|        E.|
|         |
|         |
+-----------------+
[root@655f62a4ed82 ssh]# ssh-keygen -t ed25519
Generating public/private ed25519 key pair.
Enter file in which to save the key (/root/.ssh/id_ed25519): 
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /root/.ssh/id_ed25519.
Your public key has been saved in /root/.ssh/id_ed25519.pub.
The key fingerprint is:
d8:40:95:1f:07:96:8a:83:7f:af:19:01:3b:b4:79:91 root@655f62a4ed82
The key's randomart image is:
+--[ED25519 256--+
|   ....oo   |
|   . .oo .  |
|   .+.Eo o   |
|  ..oO...   |
|   .*.S    |
|   .o..    |
|    ...    |
|     o.   |
|    o.    |
+-----------------+
[root@655f62a4ed82 ssh]# cp ~/.ssh/id_rsa.pub ~/.ssh/authorized_keys 

密钥对生成完毕后,需要修改sshd_config中上述文件所在的位置的。

HostKey /root/.ssh/id_rsa
HostKey /root/.ssh/id_dsa
HostKey /root/.ssh/id_ecdsa
HostKey /root/.ssh/id_ed25519

运行/usr/sbin/sshd,查看22端口号是否开启,开启说明启动成功。

[root@655f62a4ed82 ssh]# /usr/sbin/sshd
[root@655f62a4ed82 ssh]# lsof -i:22
COMMAND PID USER  FD  TYPE DEVICE SIZE/OFF NODE NAME
sshd   37 root  3u IPv4 250907   0t0 TCP *:ssh (LISTEN)
sshd   37 root  4u IPv6 250909   0t0 TCP *:ssh (LISTEN)

补充知识:Docker容器内运行sshd进程,远程登录闪退(Exit status 254)

注:

背景

在容器内运行了一个sshd进程,映射出一个端口供外部远程连接。可以每次连接的时候,输入密码后立即就退出了,现象如下:

[root@localhost /]# ssh root@192.168.0.6 -p 8000
root@192.168.0.6's password: 
Last login: Tue Nov 6 14:46:17 2018 from 192.168.0.6
Connection to 192.168.0.6 closed.

查看调试信息,最后退出的打印如下:

......
Connection to 192.168.0.6 closed.
Transferred: sent 2264, received 2224 bytes, in 0.0 seconds
Bytes per second: sent 235367.6, received 231209.1
debug1: Exit status 254

分析

从打印来看,已经有Last login的信息,所以密码肯定是输入正确的,也已经登录系统,那就是在初始化的环境的时候跪了。首先考虑了hosts.deny的配置,注释相关配置后问题依旧。

网上有说注释sshd配置文件中的UsePAM配置,也就是不使用pam鉴权模块,

#UsePAM yes

修改完重启sshd进程,这下果然可以了。至于原因,清一色的说是什么默认配置下,启用了超时断开连接功能。这就是在扯,默认的链接断开时间不可能这么短,而且为什么在非docker环境下sshd进程运行是正常的。我是不接受这个理由的。那就再看看呗。不使用pam鉴权就没问题,于是又挨个把/etc/pam.d/里和sshd相关的配置一个一个注释,还是没发现问题所在。

这时想到可以看看pam的日志,应该有些提示吧。顺带提一下, RedHat和CentOS的pam日志存放在/var/log/secure中,Ubuntu和Debian在 /var/log/auth.log中存储认证信息。

果然,pam里有错误信息,

可见,这是由于设置nproc、nofile、memlock等参数权限不够而导致,而这些配置是在pam组件里,由以下两个文件保存配置,

/etc/security/limits.conf

/etc/security/limits.d/90-nproc.conf

将这两个文件里面的相关设置注释,打开pam鉴权,ssh连接成功了。这才是问题所在。

另外还有其他方法

1、因为是由于权限不够导致,那就在启动容器的时候带上--privileged参数,使用特权用户,同样可以解决该问题

2、因为是在配置ulimits时错误,那么可以在启动容器时使用--ulimit=[]参数来配置

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