使用的是red hat enterprise 5 系统
现想用Source CRT远程登录red hat系统，实现Windows主机上远程操作Linux主机的目的
Source CRT为Windows上使用的串口/远程登录的客户端
使用Source CRT远程登录Linux主机有Telnet和SSH两种服务，区别在于SSH带有数据加密功能
那么Linux主机上要装有SSH服务端，并且开启了服务
1，查看是否装有SSH服务端：
[root@localhost ~]# sshd -v
sshd: illegal option -- v
OpenSSH_4.3p2, OpenSSL 0.9.8b 04 May 2006
这里表面已经装有了SSH服务端，否则的话先下载SSH服务端安装
2，查看服务是否开启：
[root@localhost ssh]# service sshd restart
停止 sshd： [失败]
启动 sshd：@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ WARNING: UNPROTECTED PRIVATE KEY FILE! @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
Permissions 0777 for '/etc/ssh/ssh_host_rsa_key' are too open.
It is recommended that your private key files are NOT accessible by others.
This private key will be ignored.
bad permissions: ignore key: /etc/ssh/ssh_host_rsa_key
Could not load host key: /etc/ssh/ssh_host_rsa_key
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ WARNING: UNPROTECTED PRIVATE KEY FILE! @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
Permissions 0777 for '/etc/ssh/ssh_host_dsa_key' are too open.
It is recommended that your private key files are NOT accessible by others.
This private key will be ignored.
bad permissions: ignore key: /etc/ssh/ssh_host_dsa_key
Could not load host key: /etc/ssh/ssh_host_dsa_key
Disabling protocol version 2. Could not load host key
sshd: no hostkeys available -- exiting.
大体上看出是密匙之类的问题，没有这个密匙，进入/etc/ssh，里面有ssh_host_dsa_key，ssh_host_rsa_key，难道是权限问题？
好吧再次生成密匙看看：
[root@localhost ~]# ssh-keygen -t dsa -f /etc/ssh/ssh_host_dsa_key
Generating public/private dsa key pair.
/etc/ssh/ssh_host_dsa_key already exists.
Overwrite (y/n)? y
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /etc/ssh/ssh_host_dsa_key.
Your public key has been saved in /etc/ssh/ssh_host_dsa_key.pub.
The key fingerprint is:
4c:63:cb:78:d9:29:fd:30:c5:c6:37:1f:81:48:93:77 root@localhost.localdomain
[root@localhost ~]# ssh-keygen -t rsa -f /etc/ssh/ssh_host_rsa_key
Generating public/private rsa key pair.
/etc/ssh/ssh_host_rsa_key already exists.
Overwrite (y/n)? y
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /etc/ssh/ssh_host_rsa_key.
Your public key has been saved in /etc/ssh/ssh_host_rsa_key.pub.
The key fingerprint is:
5a:19:3a:84:95:39:d3:91:07:68:46:90:93:85:ad:d8 root@localhost.localdomain
再次：
[root@localhost ssh]# service sshd restart
还是不行，看来是权限问题了,事实上，Ssh服务的所在文件权限太大，也不能启动该服务。
解决办法如下 ：
[root@localhost /]# cd /etc/ssh
[root@localhost ssh]# ls -l
总计 204
-rwxrwxrwx 1 root root 132839 2007-07-13 moduli
-rwxrwxrwx 1 root root 1827 2007-07-13 ssh_config
-rwxrwxrwx 1 root root 3301 2007-07-13 sshd_config
-rwxrwxrwx 1 root root 668 06-10 09:10 ssh_host_dsa_key
-rwxrwxrwx 1 root root 612 06-10 09:10 ssh_host_dsa_key.pub
-rwxrwxrwx 1 root root 963 2010-10-12 ssh_host_key
-rwxrwxrwx 1 root root 627 2010-10-12 ssh_host_key.pub
-rwxrwxrwx 1 root root 1675 06-10 09:11 ssh_host_rsa_key
-rwxrwxrwx 1 root root 408 06-10 09:11 ssh_host_rsa_key.pub
果然权限全是777，太大了，改权限吧：
[root@localhost ssh]# chmod 600 sshd_config ssh_host_dsa_key
[root@localhost ssh]# chmod 600 ssh_host_key ssh_host_rsa_key
[root@localhost ssh]# chmod 620 moduli
[root@localhost ssh]# chmod 644 ssh_config ssh_host_dsa_key.pub
[root@localhost ssh]# chmod 644 ssh_host_rsa_key
修改权限后如下：
总计 204
-rw--w---- 1 root root 132839 2007-07-13 moduli
-rw-r--r-- 1 root root 1827 2007-07-13 ssh_config
-rw------- 1 root root 3301 2007-07-13 sshd_config
-rw------- 1 root root 668 06-10 09:10 ssh_host_dsa_key
-rw-r--r-- 1 root root 612 06-10 09:10 ssh_host_dsa_key.pub
-rw------- 1 root root 963 2010-10-12 ssh_host_key
-rwxrwxrwx 1 root root 627 2010-10-12 ssh_host_key.pub
-rw-r--r-- 1 root root 1675 06-10 09:11 ssh_host_rsa_key
-rwxrwxrwx 1 root root 408 06-10 09:11 ssh_host_rsa_key.pub
重新开启ssh服务，可以了：
[root@localhost ssh]# /etc/rc.d/init.d/sshd start
[root@localhost ssh]# service sshd restart
这两个命令是等同的，使用其一即可
永久开启相关服务：可在终端下输入：setup
查看Linux主机IP：ifconfig
修改Linux主机IP：ifconfig eth0 ***.***.***.***
开网关：ifconfig eth0 up
关网关：ifconfig eth0 down
Windows上运行Source CRT，配置如下：
说明主机名为Linux主机的IP，要求与Windows主机在同一个IP段内即可
