一 問題如下:

[[email protected] tech]# yum install xinetd

Loading "installonlyn" plugin
Setting up Install Process
Setting up repositories
core                                                                 [1/4]
Cannot find a valid baseurl for repo: core
Error: Cannot find a valid baseurl for repo: core

安裝telnet-server發現yum問題, 最初認為是repo出了問題, 查詢error: cannot find a valid baseurl for repo:core, 通過網路查詢, 沒有什麼問題.比較adsl上網同實驗室上網的差異, 覺得可能是由於proxy伺服器的原因.

通過google查 yum proxy problem得如下問題解
Re: Yum proxy problem

--------------------------------------------------------------------------------

From: Jeff Vian <[email protected]>
Date: Sun, 19 Mar 2006 11:44:35 -0600

--------------------------------------------------------------------------------
On Sun, 2006-03-19 at 22:41 +0530, Sumeet Pal Singh wrote:

Hi
I installed FC4 and tried to configure yum to work. I am behind a
proxy server which requires authentication.
My /etc/yum.conf file is

[main]
cachedir=/var/cache/yum
debuglevel=2
logfile=/var/log/yum.log
pkgpolicy=newest
distroverpkg=redhat-release
tolerant=1
exactarch=1
retries=20
obsoletes=1
gpgcheck=0

# The proxy server - proxy server:port number
proxy=http://vsnlproxy.iitk.ac.in:3128/
# The account details for yum connections
proxy_username=spsingh
proxy_password=password

I had a password with % in it. When trying yum update I got HTTP Error
407 ie proxy authentication required. When i tried to search for the
problem on net, I came across this
http://beau.org/pipermail/whitebox-users/2004-March/000781.html
which shows that the guy had problem connecting because of special
character which yum could not understand/encrypt.
I did the same.Changed my password so that it had alphanumeric only
and yum worked!!!!!
Wget, apt (on ubuntu5.10 and FC4) used to work with old password.
Is this a problem with yum. Can someone please test it out!! Also can
I submit it as bug?

Not a problem but a design of the program.
% is a special character to the shell and it must be escaped so it is
passed literally or not used in most of these circumstances.

I had same problem while installing gentoo previous month. it did not
emerge and finally I gave up the installation. Can someone please test
this and let me know. i will appreciate it. My email id is
[email protected]

Thanks in Advance.

----------------------------------------------------------------

終於搞定. 雖然ssh安全可靠,但netterm的介面明顯比putty好看, 感覺上更好. 所以還是配上玩玩, 再個xinetd上以前不是掛了很多服務的嗎?慢慢玩吧, 可能service 的配置更集中, 好管理吧.

最後還是再推薦一下"鳥哥的 Linux 私房菜:"寫得太好了.

1、開啟服務

方法一：使用ntsysv,在出現的視窗之中，將 telnet前面*加上，然後按下 OK 。

方法二：編輯 /etc/xinetd.d/telnet

[[email protected] root]# vi /etc/xinetd.d/telnet

找到 disable = yes 將 yes 改成 no 。

2、啟用服務

[[email protected] root]# service xinetd restart
 

三、測試服務

[[email protected] root]#telnet ip(或者hostname）
 

如果配置正確，系統提示輸入遠端機器的使用者名稱和密碼

Login:

Password:
 

注：預設只允許普通使用者

四、設定telnet埠

#vi /etc/services

進入編輯模式後查詢telnet(vi編輯方式下輸入/telnet)

會找到如下內容：

telnet 23/tcp

telnet 23/udp
 

將23修改成未使用的埠號(如：2000)，退出vi，重啟telnet服務，telnet預設埠號就被修改了。

五、Telnet服務限制

telnet是明文傳送口令和資料的，如果你對其預設的設定不滿意，有必要對其服務範圍進行限制。假設你

的主機的ip是210.45.160.17，就可以按如下方式設定了，^_^!

#vi /etc/xinetd.d/telnet

service telnet

{

disable = no #啟用 telnet 服務,no

bind = 210.45.160.17 #your ip

only_from = 210.45.0.0/16 #只允許 210.45.0.0 ~ 210.45.255.255 這個網段進入

only_from = .edu.cn #只有教育網才能進入！

no_access = 210.45.160.{115,116} #這兩個ip不可登陸

access_times= 8:00-12:00 20:00-23:59 # 每天只有這兩個時間段開放服務

......

}
 

六、Telnet root使用者的登入

telnet 不是很安全，預設的情況之下不允許 root 以 telnet 進入 Linux 主機 。若要允許root使用者登

入，可用下列方法：

[root @wljs /root]# vi /etc/pam.d/login

#auth required pam_securetty.so #將這一行加上註釋！

或

[[email protected] root]# mv /etc/securetty /etc/securetty.bak

這樣， root 就可以直接進入 Linux 主機了。不過，建議不要這樣做。也可以在普通使用者進入後，切換

到root使用者,擁有root的許可權。