freesshd密鑰怎么連接？
ssh通過密鑰進行連接
sshd服務提供兩種安全驗證的方法：
基于口令的安全驗證:經過驗證帳號與密碼即可登陸到遠程主機。
基于密鑰的安全驗證:需要在本地生成"密鑰對"后將公鑰傳送至服務端，進行公共密鑰的比較。
使用密碼驗證終歸會存在著被駭客暴力破解或嗅探監聽的危險，其實也可以讓ssh服務基于密鑰進行安全驗證（可無需密碼驗證），步驟如下：
1.在本地主機中生成密鑰對
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[root@wluat ~]# ssh-keygen
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa): #回車或設置密鑰的存儲路徑
Created directory '/root/.ssh'.
Enter passphrase (empty for no passphrase): #回車或設置密鑰的密碼
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:
92:9e:ae:cd:eb:40:a8:7c:ad:ac:af:89:c2:ce:16:fa root@wluat
The key's randomart image is:
+--[ RSA 2048]----+
. .
. . o S
.o ... o
+.....o
=o+ .=
=BE+.o*.
+-----------------+
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注：這里為了ssh連接不要再輸入密碼，沒有輸入密碼，而是直接回車。
2.將生成好的公鑰密鑰傳送至遠程主機：
ssh-copy-id -i ~/.ssh/id_rsa.pub user@hostname
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[root@wluat ~]# ssh-copy-id 192.168.0.80
The authenticity of host '192.168.0.80 (192.168.0.80)' can't be established.
RSA key fingerprint is af:b9:dc:e7:7d:45:d7:e0:ae:24:0f:b1:a3:1f:94:48.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '192.168.0.80' (RSA) to the list of known hosts.
root@192.168.0.80's password:
Now try logging into the machine, with "ssh '192.168.0.80'", and check in:
.ssh/authorized_keys
to make sure we haven't added extra keys that you weren't expecting.
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注：其是這個就相當于在服務器端建立了~/.ssh，目錄，并將公鑰寫到了遠程主機的"~/.ssh/authorized_keys"文件中，文件的權限如下：
root@wls12c ~]$ ll .ssh
總用量 8
-rw------- 1 root root 392 8月 17 14:15 authorized_keys
-rw-r--r-- 1 root root 1586 8月 17 12:01 known_hosts
[root@wls12c ~]$ ll .ssh/authorized_keys
-rw------- 1 root root 392 8月 17 14:15 .ssh/authorized_keys
如果是傳送到遠程主機的普通用戶，authorized_keys的權限并不是600，需要手工修改，否則報如下錯誤：
[root@wluat ~]# ssh weblogic@192.168.0.80
Permission denied (publickey,gssapi-keyex,gssapi-with-mic).
或者手工復制公鑰到認證文件：
cat ~/.ssh/id_rsa.pub | ssh user@server "cat - >> ~/.ssh/authorized_keys"
3.測試，連接遠程主機的效果
ssh -i ~/.ssh/id_rsa user@hostname
[root@wluat ~]# ssh 192.168.0.80
Last login: Wed Aug 17 14:21:51 2016 from 192.168.0.150
[root@wls12c ~]$
已經實現了不要通過密碼驗證了