RHEL6解決沒法使用YUM源問題

RHEL的YUM源須要註冊用戶才能更新使用，因爲CentOS和RHEL基本沒有區別，而且CentOS已經被REHL收購。因此將RHEL的YUM源替換爲CentOS便可。
問題以下：
[root@bogon ~]# yum repolist
Loaded plugins: product-id, refresh-packagekit, security, subscription-manager
This system is not registered to Red Hat Subscription Management. You can use subscription-manager to register.
repolist: 0
或者# yum install ntp
Loaded plugins: product-id, refresh-packagekit, security, subscription-manager
This system is not registered to Red Hat Subscription Management. You can use subscription-manager to register.
Setting up Install Process
Nothing to do
解決方法：
1.清除原有RHEL的YUM及相關軟件包。
rpm -qa | grep yum | xargs rpm -e --nodeps
rpm -qa |grep python-urlgrabber|xargs rpm -e --nodeps
2.下載centos6的相關軟件包。
wget http://mirrors.163.com/centos/6/os/x86_64/Packages/yum-3.2.29-73.el6.centos.noarch.rpm
wget http://mirrors.163.com/centos/6/os/x86_64/Packages/yum-metadata-parser-1.1.2-16.el6.x86_64.rpm
wget http://mirrors.163.com/centos/6/os/x86_64/Packages/yum-plugin-fastestmirror-1.1.30-37.el6.noarch.rpm
wget http://mirrors.163.com/centos/6/os/x86_64/Packages/python-iniparse-0.3.1-2.1.el6.noarch.rpm
wget http://mirrors.163.com/centos/6/os/x86_64/Packages/python-urlgrabber-3.9.1-11.el6.noarch.rpm
*註釋:這些軟件包的具體的版本，請到http://mirrors.163.com/centos/6/os/x86_64/Packages/ 目錄下，選擇下載上述軟件包。網上不少文章無法直接使用就是由於軟件包的版本問題。

3.安裝軟件包。
rpm -ivh python-iniparse-0.3.1-2.1.el6.noarch.rpm
rpm -ivh python-urlgrabber-3.9.1-11.el6.noarch.rpm
rpm -ivh yum-metadata-parser-1.1.2-16.el6.x86_64.rpm
rpm -ivh yum-plugin-fastestmirror-1.1.30-37.el6.noarch.rpm yum-3.2.29-73.el6.centos.noarch.rpm
*註釋yum-plugin-fastestmirror和yum-3.2.29要一塊兒安裝。

若是按照遇到問題：發現錯誤，python-urlgrabber版本必須大於等於3.9.1-10
 # rpm -ivh  yum-3.2.29-73.el6.centos.noarch.rpm yum-plugin-fastestmirror-1.1.30-37.el6.noarch.rpm
warning: yum-3.2.29-73.el6.centos.noarch.rpm: Header V3 RSA/SHA1 Signature, key ID c105b9de: NOKEY
error: Failed dependencies:
    python-urlgrabber >= 3.9.1-10 is needed by yum-3.2.29-73.el6.centos.noarch
查看系統的python信息
# rpm -qa|grep python

發現python-urlgrabber-3.9.1-9.el6.noarch 版本低於3.9.1-10 
卸載：python-urlgrabber-3.9.1-9.el6.noarch
 rpm -e python-urlgrabber-3.9.1-9.el6.noarch
安裝：rpm -ivh python-urlgrabber-3.9.1-11.el6.noarch.rpm

安裝yum
# rpm -ivh yum-*
更改yum源
cd /etc/yum.repos.d/
下載配置文件
wget http://mirrors.163.com/.help/CentOS6-Base-163.repo
將此配置文件替換/etc/yum.repos.d同名文件
sed -i "s;\$releasever;6;g" CentOS6-Base-163.repo
mv rhel-source.repo rhel-source.repo.bak

或者編輯配置文件


#vim CentOS-Base.repo

把$releasever替換成現有系統的版本號(6)
vim替換命令
：%s/$releasever/6/g
退出保存

清理yum緩存
#yum clean all
將服務器軟件包信息緩存至本地，提升搜索安裝效率
#yum makecache

測試
#yum seach vim





執行yum repolist查看，若是顯示出repo倉庫列表，並顯示軟件包數量則OK。（或者使用yum makecache）


6.使用yum安裝軟件包測試。
yum -y install lrzsz

至此，若是不出現意外，lrzsz軟件包安裝成功。yum也就能夠正常使用了。


一.安裝NTP軟件包：

yum -y install ntp /*yum安裝NTP服務*/

chkconfig --add ntpd /*添加NTP*/

chkconfig ntpd on /*開機自啓動NTP*/

二.修改NTP配置文件：

vi /etc/ntp.conf
***************************************************************

# For more information about this file, see the man pages
# ntp.conf(5), ntp_acc(5), ntp_auth(5), ntp_clock(5), ntp_misc(5), ntp_mon(5).

driftfile /var/lib/ntp/drift
restrict default ignore 設置默認策略爲拒絕全部訪問方式的請求
# Permit time synchronization with our time source, but do not
# permit the source to query or modify the service on this system.
restrict default kod nomodify notrap nopeer noquery
restrict -6 default kod nomodify notrap nopeer noquery

# Permit all access over the loopback interface. This could
# be tightened as well, but to do so would effect some of
# the administrative functions.
restrict 127.0.0.1 
restrict -6 ::1

# Hosts on local network are less restricted.
restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap 容許局域網內機器同步時間

# Use public servers from the pool.ntp.org project.
# Please consider joining the pool (http://www.pool.ntp.org/join.html).
server 0.CentOS.pool.ntp.org
server 1.centos.pool.ntp.org 設置同步服務器
server 2.centos.pool.ntp.org

#broadcast 192.168.1.255 autokey # broadcast server
#broadcastclient # broadcast client
#broadcast 224.0.1.1 autokey # multicast server
#multicastclient 224.0.1.1 # multicast client
#manycastserver 239.255.254.254 # manycast server
#manycastclient 239.255.254.254 autokey # manycast client

restrict 0.centos.pool.ntp.org nomodify notrap noquery
restrict 1.centos.pool.ntp.org nomodify notrap noquery 容許與上層服務器同步時間
restrict 2.centos.pool.ntp.org nomodify notrap noquery

# Undisciplined Local Clock. This is a fake driver intended for backup
# and when no outside source of synchronized time is available. 
server 127.127.1.0 # local clock
fudge 127.127.1.0 stratum 10 外界同步源沒法聯繫時，使用本地時間爲同步服務

# Enable public key cryptography.
#crypto

includefile /etc/ntp/crypto/pw

# Key file containing the keys and key identifiers used when operating
# with symmetric key cryptography. 
keys /etc/ntp/keys

# Specify the key identifiers which are trusted.
#trustedkey 4 8 42

# Specify the key identifier to use with the ntpdc utility.
#requestkey 8

# Specify the key identifier to use with the ntpq utility.
#controlkey 8

# Enable writing of statistics records.
#statistics clockstats cryptostats loops

***************************************************************


時間同步
命令：
# ntpdate ip (同步時間服務器ip)
#hwclock -w //將時間寫入硬件
例子
ntpdate 210.167.182.10
同步時間服務器：
server
ntp-sop.inria.frserver 210.72.145.44(中國國家授時中心服務器IP地址)
server ntp.sjtu.edu.cn(上海交通大學網絡中心NTP服務器地址)

執行：
# ntpdate 210.167.182.10 (同步時間服務器ip)
#hwclock -w //將時間寫入硬件