在RaspberryPi3上的CentOS 7.2中无法使用yum

这种症状

当执行yum update时，会出现以下错误。

# yum update
読み込んだプラグイン:fastestmirror
base                            | 3.6 kB  00:00:00     
http://mirror.centos.org/altarch/7/kernel/armhfp/kernel-%24kvariant/repodata/repomd.xml: [Errno 14] HTTP Error 404 - Not Found
他のミラーを試します。
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/



 One of the configured repositories failed (CentOS Kernels for armhfp),
 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. Run the command with the repository temporarily disabled
            yum --disablerepo=centos-kernel ...

     4. Disable the repository permanently, 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 centos-kernel
        or
            subscription-manager repos --disable=centos-kernel

     5. 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=centos-kernel.skip_if_unavailable=true

failure: repodata/repomd.xml from centos-kernel: [Errno 256] No more mirrors to try.
http://mirror.centos.org/altarch/7/kernel/armhfp/kernel-$kvariant/repodata/repomd.xml: [Errno 14] HTTP Error 404 - Not Found

The reason

查看http://mirror.centos.org/altarch/7/kernel/armhfp/kernel-%24kvariant/repodata/repomd.xml这个链接时我得到了一个404错误。
虽然我不知道原因，但是当我查看目标链接（http://mirror.centos.org/altarch/7/kernel/armhfp/）时发现已经准备好了一个名为kernel-rpi2/的目录。
我的终端是RaspBerryPi3，所以我们将参考这个目录。

解决的方式

打开 /etc/yum.repos.d/CentOS-armhfp-kernel.repo 文件。

[centos-kernel]
name=CentOS Kernels for armhfp
baseurl=http://mirror.centos.org/altarch/7/kernel/$basearch/kernel-$kvariant
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
       file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-SIG-AltArch-Arm32

将此
baseurl=http://mirror.centos.org/altarch/7/kernel/$basearch/kernel-$kvariant
替换为
baseurl=http://mirror.centos.org/altarch/7/kernel/$basearch/kernel-rpi2。
再次强调，虽然是RaspBerryPi3，但没有名为rpi3的目录，所以参考rpi2。

如果可以更改，那么执行 yum clean all 然后执行 yum update。

我认为这应该没有问题，可以顺利更新！