背景，需要安裝cacti，google了很多安裝資料，需要先yum安裝一些准備lib包，比如snmp以及openssl等等。
[root@mysqlvm2 ~]# yum install net-snmp-devel
Loaded plugins: rhnplugin, security
This system is not registered with RHN.
RHN support will be disabled.
Setting up Install Process
No package net-snmp-devel available.
Nothing to do
看到yum不識別，所以需要先在linux服務器上面安裝yum軟件包。
推薦閱讀：
RedHat Linux 本地yum源的配置 http://www.linuxidc.com/Linux/2013-08/88217.htm
RedHat 6.2 Linux修改yum源免費使用CentOS源 http://www.linuxidc.com/Linux/2013-07/87383.htm
配置EPEL YUM源 http://www.linuxidc.com/Linux/2012-10/71850.htm
Redhat 本地yum源配置 http://www.linuxidc.com/Linux/2012-11/75127.htm
yum的配置文件說明 http://www.linuxidc.com/Linux/2013-04/83298.htm
RedHat 6.1下安裝yum(圖文) http://www.linuxidc.com/Linux/2013-06/86535.htm
YUM 安裝及清理 http://www.linuxidc.com/Linux/2013-07/87163.htm
1 下載yum安裝包
下載地址：wget http://yum.baseurl.org/download/3.4/yum-3.4.3.tar.gz
[root@mysqlvm2 ~]# wget http://yum.baseurl.org/download/3.4/yum-3.4.3.tar.gz
--2014-05-15 20:56:34-- http://yum.baseurl.org/download/3.4/yum-3.4.3.tar.gz
正在解析主機 yum.baseurl.org... 140.211.167.207
Connecting to yum.baseurl.org|140.211.167.207|:80... 已連接。
已發出 HTTP 請求，正在等待回應... 200 OK
長度：1140370 (1.1M) [application/x-gzip]
Saving to: `yum-3.4.3.tar.gz\
2 解壓縮安裝
tar -xvf yum-3.4.3.tar.gz
cd yum-3.4.3
yum main.py install yum
[root@mysqlvm2 yum-3.4.3]# yum main.py install yum
Loaded plugins: rhnplugin, security
This system is not registered with RHN.
RHN support will be disabled.
usage: yum [options] COMMAND
List of Commands:
紅帽中出現This system is not registered with RHN這個的原因是因為紅帽中沒有注冊RHN。解決辦法：（假定你已安裝yum，且網絡暢通）更改yum的源，即更換/etc/yum.repos.d /rhel-debuginfo.repo 這個文件。進入/etc/yum.repos.d/目錄，終端中輸入wget http://docs.linuxtone.org/soft/lemp/CentOS-Base.repo即可在此目錄下得到CentOS- Base.repo文件，這是centos的源文件，只需將其重命名為rhel-debuginfo.repo即可，以前的文件做個備份。
wget http://www.linuxidc.com/files/2011/05/06/CentOS-Base.repo
cp /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.bak
[root@localhost yum.repos.d]# cp rhel-debuginfo.repo rhel-debuginfo.repo.bak
[root@localhost yum.repos.d]# mv CentOS-Base.repo rhel-debuginfo.repo
mv：是否覆蓋“rhel-debuginfo.repo”? y
[root@localhost yum.repos.d]#
[root@mysqlvm2 yum-3.4.3]# yum makecache
Loaded plugins: rhnplugin, security
This system is not registered with RHN.
RHN support will be disabled.
addons | 1.9 kB 00:00
addons/filelists_db | 570 B 00:00
addons/other_db | 554 B 00:00
addons/primary_db
[root@mysqlvm2 yum-3.4.3]# yum install httpd
Loaded plugins: rhnplugin, security
This system is not registered with RHN.
RHN support will be disabled.
Setting up Install Process
Package httpd-2.2.3-85.el5.centos.x86_64 already installed and latest version
Nothing to do
更多詳情見請繼續閱讀下一頁的精彩內容： http://www.linuxidc.com/Linux/2014-06/103814p2.htm