問題描述

在yum check-update的時候，總是提示錯誤。按照網上的方法做處理，結果提示各種錯誤，大致如下：

• YumRepo Error: All mirror URLs are not using ftp, http[s] or file
• Error: Cannot retrieve repository metadata (repomd.xml) for repository: addons.
• Loaded plugins: fastestmirror, refresh-packagekit, security Loading mirror speeds from cached hostfi

試了網上解決方案，我的問題均未解決。最後自己試出來了，先說明下大概情況：
1.最新版的CentOS系統是7.4.1708，如圖

2.國內的各大映象站只有最新版本目錄有內容，其他版本目錄下僅有readme檔案
3.各大映象站下載的CentOS-Base.repo檔案，放到/etc/yum.repos.d/下都用不了

解決方案

在readme檔案中發現http://vault.centos.org/網站是有各個版本映象的，所以
1.通過lsb_release -a查詢下，系統版本如圖

2.根據查詢資訊，將/etc/yum.repos.d/CentOS-Base.repo中baseurl路徑做調整,檔案內容如下：

# 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-$releasever - Base
baseurl=http://vault.centos.org/5.5/os/i386/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5
#released updates 
[updates]
name=CentOS-$releasever - Updates
baseurl=http://vault.centos.org/5.5/updates/i386/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5
#packages used/produced in the build but not released
[addons]
name=CentOS-$releasever - Addons
baseurl=http://vault.centos.org/5.5/addons/i386/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5
#additional packages that may be useful
[extras]
name=CentOS-$releasever - Extras
baseurl=http://vault.centos.org/5.5/extras/i386/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-$releasever - Plus
baseurl=http://vault.centos.org/5.5/centosplus/i386/
gpgcheck=1
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5
#contrib - packages by Centos Users
[contrib]
name=CentOS-$releasever - Contrib
baseurl=http://vault.centos.org/5.5/contrib/i386/
gpgcheck=1
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5

3.儲存檔案後，執行yum clean all
4.執行yum check-update測試下，ok

國內的幾個yum映象源

1. http://ftp.sjtu.edu.cn/centos/，上海交大，但伺服器位於北京，中國教育網網路中心，我看像是朝陽區那邊的IP，以前在那邊上過 班，下載速度高達十M。 北方使用者與教育網使用者推薦，速度飛快。
2. http://mirrors.sohu.com/，sohu的開源映象伺服器，伺服器位於山東省聯通。 速度飛快，全國使用者推薦，經常用FireFox下載CD映象。
3. http://mirrors.163.com/centos，網易的開源伺服器映象 速度也不錯，全國使用者推薦. 下載CentOS-Base-163.repo, 放入/etc/yum.repos.d/