Q：sudo xxx的时候提示“xxx不在sudoers列表中”

A：

gvim /etc/sudoers
#在root后面添加一行
root    ALL=(ALL)       ALL
lee     ALL=(ALL)       ALL

Q：修改源列表

网络源+光盘源(先弄网络源)
cd /etc/yum.repos.d/
gvim CentOS-Base.repo

修改的源列表
# 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-$releasever - Base
mirrorlist=http://http://mirror.zjustu.org/centos/$releasever/os/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os
#baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/
gpgcheck=1
gpgkey=http://mirror.zjustu.org/centos/RPM-GPG-KEY-CentOS-6
#gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6
 
#released updates 
[updates]
name=CentOS-$releasever - Updates
mirrorlist=http://http://mirror.zjustu.org/centos/$releasever/updates/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updates
#baseurl=http://mirror.centos.org/centos/$releasever/updates/$basearch/
gpgcheck=1
gpgkey=http://mirror.zjustu.org/centos/RPM-GPG-KEY-CentOS-6
#gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6
 
#additional packages that may be useful
[extras]
name=CentOS-$releasever - Extras
mirrorlist=http://http://mirror.zjustu.org/centos/$releasever/extras/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=extras
#baseurl=http://mirror.centos.org/centos/$releasever/extras/$basearch/
gpgcheck=1
gpgkey=http://mirror.zjustu.org/centos/RPM-GPG-KEY-CentOS-6
#gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6
 
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-$releasever - Plus
mirrorlist=http://http://mirror.zjustu.org/centos/$releasever/centosplus/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=centosplus
#baseurl=http://mirror.centos.org/centos/$releasever/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirror.zjustu.org/centos/RPM-GPG-KEY-CentOS-6
#gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6
 
#contrib - packages by Centos Users
[contrib]
name=CentOS-$releasever - Contrib
mirrorlist=http://http://mirror.zjustu.org/centos/$releasever/contrib/$basearch
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=contrib
#baseurl=http://mirror.centos.org/centos/$releasever/contrib/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirror.zjustu.org/centos/RPM-GPG-KEY-CentOS-6
#gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6

参照http://lug.ustc.edu.cn/wiki/mirrors/help/centos 进行的修改