CentOS 7.2：Yum 存储库配置失败

Question

全新安装 CentOS 7.2.1511。服务器最初是用网络管理器配置的，yum 工作正常。最近禁用了网络管理器并使用传统服务 (/etc/sysconfig/network-scripts) 配置了网络。新的 IP 地址已分配给 NIC。安装程序最初在 10.xxx 网络上，现在在 192.168.xx 网络上。

当我尝试运行 yum 时，出现以下错误：

Loaded plugins: fastestmirror, langpacks
http://mirror.centos.org/centos/%24releasever/os/x86_64/repodata/repomd.xml: [Errno 14] HTTP Error 404 - Not Found
Trying other mirror.
To address this issue please refer to the below knowledge base article 

https://access.redhat.com/articles/1320623

If above article doesn't help to resolve this issue please create a bug on https://bugs.centos.org/

http://mirror.centos.org/centos/%24releasever/extras/x86_64/repodata/repomd.xml: [Errno 14] HTTP Error 404 - Not Found
Trying other mirror.


 One of the configured repositories failed (CentOS-$releasever - Extras),
 and yum doesn't have enough cached data to continue. At this point the only
 safe thing yum can do is fail. There are a few ways to work "fix" this:

 1. Contact the upstream for the repository and get them to fix the problem.

 2. Reconfigure the baseurl/etc. for the repository, to point to a working
    upstream. This is most often useful if you are using a newer
    distribution release than is supported by the repository (and the
    packages for the previous distribution release still work).

 3. Disable the repository, so yum won't use it by default. Yum will then
    just ignore the repository until you permanently enable it again or use
    --enablerepo for temporary usage:

        yum-config-manager --disable extras

 4. Configure the failing repository to be skipped, if it is unavailable.
    Note that yum will try to contact the repo. when it runs most commands,
    so will have to try and fail each time (and thus. yum will be be much
    slower). If it is a very temporary problem though, this is often a nice
    compromise:

        yum-config-manager --save --setopt=extras.skip_if_unavailable=true

failure: repodata/repomd.xml from extras: [Errno 256] No more mirrors to try.
http://mirror.centos.org/centos/$releasever/extras/x86_64/repodata/repomd.xml: [Errno 14] HTTP Error 404 - Not Found

以下是网络接口的设置。em1 和 em2 具有相同的基本配置：

TYPE=Ethernet
BOOTPROTO=none
DEFROUTE=yes
PEERDNS=yes
PEERROUTES=yes
NAME=em1
NM_CONTROLLED=no
IPV4_FAILURE_FATAL=no
UUID=d67971e8-846d-428c-9a1d-ff2768ae6ddb
DEVICE=em1
HWADDR=14:18:77:69:D5:DB
ONBOOT=yes
IPADDR=192.168.x.x
NETMASK=255.255.255.0
GATEWAY=192.168.x.x

我的 /etc/hosts 文件：

127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
192.168.x.x hostname

我的 /etc/resolv.conf 文件：

nameserver 68.105.28.12
nameserver 68.105.29.11

我的 CentOS-Base.repo 文件。我取消了 baseurl 设置的注释，以查看它是否有效：

# 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=$basearch&repo=os&infra=$infra
baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
skip_if_unavailable = 1
keepcache = 0

#released updates 
[updates]
name=CentOS-$releasever - Updates
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updates&infra=$infra
baseurl=http://mirror.centos.org/centos/$releasever/updates/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7

#additional packages that may be useful
[extras]
name=CentOS-$releasever - Extras
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=extras&infra=$infra
baseurl=http://mirror.centos.org/centos/$releasever/extras/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7

#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-$releasever - Plus
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=centosplus&infra=$infra
baseurl=http://mirror.centos.org/centos/$releasever/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7

yum repolist 的结果：

Loaded plugins: fastestmirror, langpacks
http://mirror.centos.org/centos/%24releasever/os/x86_64/repodata/repomd.xml:   [Errno 14] HTTP Error 404 - Not Found
Trying other mirror.
To address this issue please refer to the below knowledge base article 

https://access.redhat.com/articles/1320623

If above article doesn't help to resolve this issue please create a bug on   https://bugs.centos.org/

  http://mirror.centos.org/centos/%24releasever/extras/x86_64/repodata/repomd.xml: [Errno 14] HTTP Error 404 - Not Found
Trying other mirror.
http://mirror.centos.org/centos/%24releasever/extras/x86_64/repodata/repomd.xml: [Errno 14] HTTP Error 404 - Not Found
Trying other mirror.
http://mirror.centos.org/centos/%24releasever/updates/x86_64/repodata/repomd.xml: [Errno 14] HTTP Error 404 - Not Found
Trying other mirror.
repo id                                                                           repo name                                                                         status
extras/$releasever/x86_64                                                       CentOS-$releasever - Extras                                                   0
updates/$releasever/x86_64                                                  CentOS-$releasever - Updates                                                  0
repolist: 0

卷曲结果：

curl 'http://mirrorlist.centos.org/?release=6&arch=i386&repo=os'
http://mirrors.usc.edu/pub/linux/distributions/centos/6.8/os/i386/
http://mirror.lug.udel.edu/pub/centos/6.8/os/i386/
http://mirrors.lga7.us.voxel.net/centos/6.8/os/i386/
http://mirror.chpc.utah.edu/pub/centos/6.8/os/i386/
http://centos.unixheads.org/6.8/os/i386/
http://centos.mirror.lstn.net/6.8/os/i386/
http://centos.mirror.nac.net/6.8/os/i386/
http://mirror.tocici.com/centos/6.8/os/i386/
http://mirror.supremebytes.com/centos/6.8/os/i386/
http://mirror.steadfast.net/centos/6.8/os/i386/

我可以 ping 外部主机并可以挖掘域名：

dig cnn.com

; <<>> DiG 9.9.4-RedHat-9.9.4-29.el7_2.3 <<>> cnn.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 29420
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;cnn.com.           IN  A

;; ANSWER SECTION:
cnn.com.        156 IN  A   157.166.226.26
cnn.com.        156 IN  A   157.166.226.25

;; Query time: 1 msec
;; SERVER: 68.105.28.12#53(68.105.28.12)
;; WHEN: Mon Jun 20 12:28:44 EDT 2016
;; MSG SIZE  rcvd: 68

我确定这与 em1 和 em2 的旧配置有关，当它们绑定到不同的 IP 地址时，但我不知道还能在哪里查看。我可能会错过什么让 yum 工作？

Answer 1

经过更多的侦查，我想通了。缺少目录层次结构，yum 无法检测到我的 CentOS 版本。运行以下命令修复它：

mkdir -p /etc/yum/vars
echo 7.2.1511 > /etc/yum/vars/releasever

如果您遇到此问题并且没有其他任何工作，请将“7.2.1511”替换为您自己的发行版本。

2017 年 5 月 21 日更新：“7.2.1511”路径已被弃用。如果您仍然使用 CentOS 7.2.1511，请运行以下命令以保持 yum 工作：

echo 7 > /etc/yum/vars/releasever

如果您突然发现 yum 已停止工作，那应该解决它。