廢話不多說，下面記錄了centos下更換系統預設yum源為網易yum源的操作過程：
1）備份原有的預設yum源
[root@bastion-IDC ~]# cp /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.bak
2）修改CentOS-Base.repo檔案。將檔案中的baseurl地址修改為網易163的yum源地址即可！
[root@bastion-IDC ~]# vim /etc/yum.repos.d/CentOS-Base.repo
# CentOS-Base.repo # # The mirror system uses the connecting IP address of the client and the # update status of each mirror to pick mirrors that are updated to and # geographically close to the client. You should use this for CentOS updates # unless you are manually picking other mirrors. # # If the mirrorlist= does not work for you, as a fall back you can try the # remarked out baseurl= line instead. # # [base] name=CentOS-$releasever - Base #mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os baseurl=http://mirrors.163.com/centos/$releasever/os/$basearch/ gpgcheck=1 gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-6 #released updates [updates] name=CentOS-$releasever - Updates #mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updates baseurl=http://mirrors.163.com/centos/$releasever/updates/$basearch/ gpgcheck=1 gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-6 #additional packages that may be useful [extras] name=CentOS-$releasever - Extras #mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=extras baseurl=http://mirrors.163.com/centos/$releasever/extras/$basearch/ gpgcheck=1 gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-6 #additional packages that extend functionality of existing packages [centosplus] name=CentOS-$releasever - Plus #mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=centosplus baseurl=http://mirrors.163.com/centos/$releasever/centosplus/$basearch/ gpgcheck=1 enabled=0 gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-6 #contrib - packages by Centos Users [contrib] name=CentOS-$releasever - Contrib #mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=contrib baseurl=http://mirrors.163.com/centos/$releasever/contrib/$basearch/ gpgcheck=1 enabled=0 gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-6
[root@bastion-IDC ~]# yum clean all
[root@bastion-IDC ~]# yum makecache //將伺服器上的軟體包資訊快取到本地,以提高搜尋安裝軟體的速度
[root@bastion-IDC ~]# yum update //更新系統
依照上面操作後，yum源就更換成網易的了，並能正常使用。
要特別注意的是：如果要想CentOS使用yum update更新時不升級核心，方法如下：
[root@bastion-IDC ~]# cp /etc/yum.conf /etc/yum.confbak
方法一）修改yum的配置檔案
[root@bastion-IDC ~]# vim /etc/yum.conf
在[main]的最後新增 exclude=kernel*
方法二）直接在yum的命令後面加上如下的引數：
[root@bastion-IDC ~]# yum --exclude=kernel* update
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如果要更換成阿里雲的yum源，只需要將/etc/yum.repos.d/CentOS-Base.repo內容替換成下面內容即可，然後yum clean all、yum makecache、yum update
# CentOS-Base.repo
#
# The mirror system uses the connecting IP address of the client and the
# update status of each mirror to pick mirrors that are updated to and
# geographically close to the client. You should use this for CentOS updates
# unless you are manually picking other mirrors.
#
# If the mirrorlist= does not work for you, as a fall back you can try the
# remarked out baseurl= line instead.
#
#
[base]
name=CentOS-$releasever - Base - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/os/$basearch/
http://mirrors.aliyuncs.com/centos/$releasever/os/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os
gpgcheck=1
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-6
#released updates
[updates]
name=CentOS-$releasever - Updates - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/updates/$basearch/
http://mirrors.aliyuncs.com/centos/$releasever/updates/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updates
gpgcheck=1
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-6
#additional packages that may be useful
[extras]
name=CentOS-$releasever - Extras - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/extras/$basearch/
http://mirrors.aliyuncs.com/centos/$releasever/extras/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=extras
gpgcheck=1
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-6
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-$releasever - Plus - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/centosplus/$basearch/
http://mirrors.aliyuncs.com/centos/$releasever/centosplus/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=centosplus
gpgcheck=1
enabled=0
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-6
#contrib - packages by Centos Users
[contrib]
name=CentOS-$releasever - Contrib - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/contrib/$basearch/
http://mirrors.aliyuncs.com/centos/$releasever/contrib/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=contrib
gpgcheck=1
enabled=0
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-6
[root@bastion-IDC ~]# yum clean all
[root@bastion-IDC ~]# yum makecache
如果出現下面報錯：
https://mirrors.aliyun.com/centos/$releasever/os/x86_64/repodata/repomd.xml: [Errno 14] PYCURL ERROR 22 - "The requested URL returned error: 404 Not Found"
原因分析：
$releasever這個變數在CentOS-Base.repo檔案中沒有被識別出來。可以去aliyun的映象官網上檢視下正確地址：
即正確地址是：https://mirrors.aliyun.com/centos/6.9/os/x86_64/repodata/repomd.xml
解決辦法：將$releasever換成6.9
[root@bastion-IDC ~]# sed -i 's/$releasever/6.9/g' CentOS-Base.repo
==================================================================
如果更換成163的yum源, 出現這種問題, 即"http://mirrors.163.com/centos/6/os/x86_64/repodata/repomd.xml: [Errno 14] PYCURL ERROR 22 - "The requested URL returned error: 404 Not Found"", 解決方法和上面是一樣的, 也是到http://mirrors.163.com/centos下檢視哪個6.x/os/x86_64/repodata/repomd.xml下存在這個檔案, 然後把CentOS-Base.repo檔案中的$releasever全部更換為這個6.x即可!