随记：RHEL修改yum源
安装了RHEL6.2准备学习邮件系统安装配置，发现忘记安装C环境，准备yum一下又悲催的发现yum不能用。对于我这种懒人，最不耐烦就是一个个的去下载各种包，还是决定拿yum开刀
由于RHEL默认的yum源需要注册（有费用，对于我等学习型选手实在没必要），但又想使用yum方便安装些软件，于是只能考虑修改更新源（其实默认的站点在国外，改成国内的反而更好）。那么理所当然的想到了RedHat的全职小弟CentOS
我使用的是网易镜像
下载repo文件
cd /etc/yum.repos.d
wget http://mirrors.163.com/.help/CentOS6-Base-163.repo
mv CentOS6-Base-163.repo CentOS-Base.repo //不改名我第一次试不行，改完好了，不知道是不是名字的问题
修改repo文件
vi CentOS-Base.repo
:%s/\$releasever/6/g //把版本变量替换成6，整个文件如下
1: # CentOS-Base.repo
2: #
3: # The mirror system uses the connecting IP address of the client and the
4: # update status of each mirror to pick mirrors that are updated to and
5: # geographically close to the client. You should use thisfor CentOS updates
6: # unless you are manually picking other mirrors.
7: #
8: # If the mirrorlist= does not work for you, as a fall back you can try the
9: # remarked out baseurl= line instead.
10: #
11: #
12:
13: [base]
14: name=CentOS-6 - Base - 163.com
15: baseurl=http://mirrors.163.com/centos/6/os/$basearch/
16: #mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os
17: gpgcheck=1
18: gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6
19:
20: #released updates
21: [updates]
22: name=CentOS-6 - Updates - 163.com
23: baseurl=http://mirrors.163.com/centos/6/updates/$basearch/
24: #mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updates
25: gpgcheck=1
26: gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6
27:
28: #additional packages that may be useful
29: [extras]
30: name=CentOS-6 - Extras - 163.com
31: baseurl=http://mirrors.163.com/centos/6/extras/$basearch/
32: #mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=extras
33: gpgcheck=1
34: gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6
35:
36: #additional packages that extend functionality of existing packages
37: [centosplus]
38: name=CentOS-6 - Plus - 163.com
39: baseurl=http://mirrors.163.com/centos/6/centosplus/$basearch/
40: #mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=centosplus
41: gpgcheck=1
42: enabled=0
43: gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6
44:
45: #contrib - packages by Centos Users
46: [contrib]
47: name=CentOS-6 - Contrib - 163.com
48: baseurl=http://mirrors.163.com/centos/6/contrib/$basearch/
49: #mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=contrib
50: gpgcheck=1
51: enabled=0
52: gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6
53:
导入GPG key
rpm --import http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-6
好了，打完收工，测试下
yum clean all
yum makecache
都通过了
补充：
细看文件结构其实很简单
name= //系统名称(标示而已)
baseurl= //url地址
gpgcheck= //gpg检查，可选，若为1则后面要制定gpgkey位置，如无默认为0
enabled= //可选，如无则默认为1,
gpgkey= //gpgkey地址
如此完全可以构建基于本地光盘的yum（当然只是基本的安装包）
echo "[base]">local.repo
echo "name=RHEL6" >>local.repo
echo "baseurl=file:///mnt/Server" >>local.repo
echo "enabled=1" >>local.repo
mount /dev/sr0 /mnt