作者： kiccleaf

首先我们找到系统下/etc/ssh/sshd_config 文件并用 ee /etc/ssh/sshd_config 打开内容如下：

# $OpenBSD: sshd_config,v 1.80 2008/07/02 02:24:18 djm Exp $
# $FreeBSD: src/crypto/openssh/sshd_config,v 1.49.2.1.2.1 2009/10/25 01:10:29 kensmith
Exp $
# This is the sshd server system-wide configuration file.  See
# sshd_config(5) for more information.
# This sshd was compiled with PATH=/usr/bin:/bin:/usr/sbin:/sbin
# The strategy used for options in the default sshd_config shipped with
# OpenSSH is to specify options with their default value where
# possible, but leave them commented.  Uncommented options change a
# default value.
# Note that some of FreeBSD's defaults differ from OpenBSD's, and
# FreeBSD has a few additional options.
#VersionAddendum FreeBSD-20090522
Port 222  #可修改端口号，防止攻击，默认为22端口
#Protocol 2
#AddressFamily any
#ListenAddress 0.0.0.0
#ListenAddress ::
# Disable legacy (protocol version 1) support in the server for new
# installations. In future the default will change to require explicit
# activation of protocol 1
Protocol 2
# HostKey for protocol version 1
#HostKey /etc/ssh/ssh_host_key
# HostKeys for protocol version 2
#HostKey /etc/ssh/ssh_host_rsa_key
#HostKey /etc/ssh/ssh_host_dsa_key
# Lifetime and size of ephemeral version 1 server key
#KeyRegenerationInterval 1h
#ServerKeyBits 1024
# Logging
# obsoletes QuietMode and FascistLogging
#SyslogFacility AUTH
#LogLevel INFO
# Authentication:
#LoginGraceTime 2m
PermitRootLogin no    #是否允许ROOT用户直接登陆系统 yes  是  no 否
#StrictModes yes
#MaxAuthTries 6
#MaxSessions 10
#RSAAuthentication yes
#PubkeyAuthentication yes
AuthorizedKeysFile .ssh/id_dsa.pub  #修改使用用户目录下KEY公共文件
# For this to work you will also need host keys in /etc/ssh/ssh_known_hosts
#RhostsRSAAuthentication no
# similar for protocol version 2
#HostbasedAuthentication no
# Change to yes if you don't trust ~/.ssh/known_hosts for
# RhostsRSAAuthentication and HostbasedAuthentication
#IgnoreUserKnownHosts no
# Don't read the user's ~/.rhosts and ~/.shosts files
#IgnoreRhosts yes
# Change to yes to enable built-in password authentication.
#修改可以密码进行登陆
PasswordAuthentication no     # 不允许用户使用密码方式登录
PermitEmptyPasswords no       # 禁止空密码的用户进行登录
# Change to no to disable PAM authentication
#ChallengeResponseAuthentication yes
# Kerberos options
#KerberosAuthentication no
#KerberosOrLocalPasswd yes
#KerberosTicketCleanup yes
#KerberosGetAFSToken no
# GSSAPI options
#GSSAPIAuthentication no
#GSSAPICleanupCredentials yes
# Set this to 'no' to disable PAM authentication, account processing,
# and session processing. If this is enabled, PAM authentication will
# be allowed through the ChallengeResponseAuthentication and
# PasswordAuthentication.  Depending on your PAM configuration,
# PAM authentication via ChallengeResponseAuthentication may bypass
# the setting of "PermitRootLogin without-password".
# If you just want the PAM account and session checks to run without
# PAM authentication, then enable this but set PasswordAuthentication
# and ChallengeResponseAuthentication to 'no'.
#UsePAM yes
#AllowAgentForwarding yes
#AllowTcpForwarding yes
#GatewayPorts no
#X11Forwarding yes
#X11DisplayOffset 10
#X11UseLocalhost yes
#PrintMotd yes
#PrintLastLog yes
#TCPKeepAlive yes
#UseLogin no
#UsePrivilegeSeparation yes
#PermitUserEnvironment no
#Compression delayed
#ClientAliveInterval 0
#ClientAliveCountMax 3
#UseDNS yes
#PidFile /var/run/sshd.pid
#MaxStartups 10
#PermitTunnel no
#ChrootDirectory none
# no default banner path
#Banner none
# override default of no subsystems
Subsystem sftp /usr/libexec/sftp-server
# Example of overriding settings on a per-user basis
#Match User anoncvs
# X11Forwarding no
# AllowTcpForwarding no
# ForceCommand cvs server
OK，以上SSH配置修改完成！进行重启SSH服务，
leaf# /etc/rc.d/sshd restart
Stopping sshd.
Starting sshd.
进入下一步生成Key
leaf# ssh-keygen -t dsa   输入生成语句
Generating public/private dsa key pair.
Enter file in which to save the key (/root/.ssh/id_dsa):  # 默认回车即可，或是选择你要存放的位置
Created directory '/root/.ssh'.
Enter passphrase (empty for no passphrase):  #输入密匙的密码
Enter same passphrase again:     #再次输入密匙的密码
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:
11:d6:63:26:84:fc:4f:6d:c3:9a:fa:50:ff:08:f4:0b root@leaf
The key's randomart image is:
+--[ DSA 1024]----+
|     . o+.       |
|      o...=      |
|       ..+ +     |
|        ... =    |
|        Soo+ .   |
|         o+o     |
|        ..E o    |
|        .. o +   |
|         .. o .  |
+-----------------+
leaf# ll /root/  #查看root目录是否生成了.ssh目录
total 16
-rw-r--r--  2 root  wheel   812 Mar  9 06:53 .cshrc
-rw-------  1 root  wheel  2369 Mar 10 07:26 .history
-rw-r--r--  1 root  wheel   155 Nov 21 22:57 .k5login
-rw-r--r--  1 root  wheel   303 Nov 21 22:57 .login
-rw-------  1 root  wheel   332 Feb  4 00:55 .mysql_history
-rw-r--r--  2 root  wheel   265 Nov 21 22:57 .profile
drwx------  2 root  wheel   512 Mar 12 06:37 .ssh
leaf# ll /root/.ssh/  #查看.ssh目录下是否有id_dsa 和id_dsa.pub 两个文件
total 4
-rw-------  1 root  wheel  736 Mar 12 06:37 id_dsa      #确认私钥已经建立
-rw-r--r--  1 root  wheel  603 Mar 12 06:37 id_dsa.pub  #确认公钥已经建立

接下去下载id_dsa 文件，并配置到相应的用户SSH登陆软件中。记住下载完id_dsa文件后，记得删除id_dsa文件！
执行以下操作：
leaf# rm -r id_dsa