1、事件描述：CentOS7下使用tree指令，發現該指令沒有被安裝，在安裝的過程中發現yum報錯
<code>[root@openstack-01 ~]</code><code># tree -d</code>
<code>bash</code><code>: tree: 未找到指令...</code>
<code>[root@openstack-01 ~]</code><code># yum -y install tree</code>
<code>已加載插件：fastestmirror, langpacks</code>
<code>Repodata is over 2 weeks old. Install yum-</code><code>cron</code><code>? Or run: yum makecache fast</code>
2、處理過程
a、直接執行yum makecache fast
[root@openstack-01 ~]# yum makecache fast
已加載插件：fastestmirror, langpacks
Repodata is over 2 weeks old. Install yum-cron? Or run: yum makecache fast
備注：根據它的提示資訊執行操作，發現提示資訊依舊
b、清除yum緩存
<code>[root@openstack-01 ~]</code><code># yum clean all</code>
<code>正在清理軟體源： base centos-ceph-hammer centos-openstack-mitaka centos-qemu-ev extras updates</code>
<code>Cleaning up everything</code>
<code>Cleaning up list of fastest mirrors</code>
<code>[5]- 已殺死 yum update</code>
<code>[root@openstack-01 ~]</code><code># yum makecache</code>
<code>Could not retrieve mirrorlist http:</code><code>//mirrorlist</code><code>.centos.org/?release=7&arch=x86_64&repo=os&infra=stock error was</code>
<code>14: curl</code><code>#6 - "Could not resolve host: mirrorlist.centos.org; 未知的錯誤"</code>
<code> </code><code>One of the configured repositories failed (未知),</code>
<code> </code><code>and yum doesn't have enough cached data to </code><code>continue</code><code>. At this point the only</code>
<code> </code><code>safe thing yum can </code><code>do</code> <code>is fail. There are a few ways to work </code><code>"fix"</code> <code>this:</code>
<code> </code><code>1. Contact the upstream </code><code>for</code> <code>the repository and get them to fix the problem.</code>
<code> </code><code>2. Reconfigure the baseurl</code><code>/etc</code><code>. </code><code>for</code> <code>the repository, to point to a working</code>
<code> </code><code>upstream. This is most often useful </code><code>if</code> <code>you are using a newer</code>
<code> </code><code>distribution release than is supported by the repository (and the</code>
<code> </code><code>packages </code><code>for</code> <code>the previous distribution release still work).</code>
<code> </code><code>3. Disable the repository, so yum won't use it by default. Yum will </code><code>then</code>
<code> </code><code>just ignore the repository </code><code>until</code> <code>you permanently </code><code>enable</code> <code>it again or use</code>
<code> </code><code>--enablerepo </code><code>for</code> <code>temporary usage:</code>
<code> </code><code>yum-config-manager --disable <repoid></code>
<code> </code><code>4. Configure the failing repository to be skipped, </code><code>if</code> <code>it is unavailable.</code>
<code> </code><code>Note that yum will try to contact the repo. when it runs most commands,</code>
<code> </code><code>so will have to try and fail each </code><code>time</code> <code>(and thus. yum will be be much</code>
<code> </code><code>slower). If it is a very temporary problem though, this is often a </code><code>nice</code>
<code> </code><code>compromise:</code>
<code> </code><code>yum-config-manager --save --setopt=<repoid>.skip_if_unavailable=</code><code>true</code>
<code>Cannot </code><code>find</code> <code>a valid baseurl </code><code>for</code> <code>repo: base</code><code>/7/x86_64</code>
這時候我開始懷疑是不是我的yum所在的網絡也存在問題
c、檢測網絡連通性狀态，發現的确是網絡存在問題
<code>檢查了網卡配置，發現DNS配置存在一些問題，手動修改并重置網卡資訊，網絡恢複正常</code>
<code>base | 3.6 kB 00:00:00 </code>
<code>centos-ceph-hammer | 2.9 kB 00:00:00 </code>
<code>centos-openstack-mitaka | 2.9 kB 00:00:00 </code>
<code>centos-qemu-ev | 2.9 kB 00:00:00 </code>
<code>extras | 3.4 kB 00:00:00 </code>
<code>updates | 3.4 kB 00:00:00 </code>
<code>(1</code><code>/7</code><code>): centos-ceph-hammer</code><code>/7/x86_64/primary_db</code> <code>| 30 kB 00:00:01 </code>
<code>(2</code><code>/7</code><code>): extras</code><code>/7/x86_64/primary_db</code> <code>| 132 kB 00:00:00 </code>
<code>(3</code><code>/7</code><code>): updates</code><code>/7/x86_64/primary_db</code> <code>| 4.9 MB 00:00:01 </code>
<code>(4</code><code>/7</code><code>): centos-openstack-mitaka</code><code>/x86_64/primary_db</code> <code>| 452 kB 00:00:04 </code>
<code>(5</code><code>/7</code><code>): base</code><code>/7/x86_64/primary_db</code> <code>| 5.3 MB 00:00:07 </code>
<code>(6</code><code>/7</code><code>): base</code><code>/7/x86_64/group_gz</code> <code>| 155 kB 00:00:15 </code>
<code>(7</code><code>/7</code><code>): centos-qemu-ev</code><code>/7/x86_64/primary_db</code> <code>| 23 kB 00:00:16 </code>
<code>Determining fastest mirrors</code>
<code> </code><code>* base: mirrors.zju.edu.cn</code>
<code> </code><code>* extras: mirrors.aliyun.com</code>
<code> </code><code>* updates: mirrors.aliyun.com</code>
<code>正在解決依賴關系</code>
<code>--> 正在檢查事務</code>
<code>---> 軟體包 tree.x86_64.0.1.6.0-10.el7 将被 安裝</code>
<code>--> 解決依賴關系完成</code>
<code>依賴關系解決</code>
<code>====================================================================================================================================================</code>
<code> </code><code>Package 架構 版本 源 大小</code>
<code>正在安裝:</code>
<code> </code><code>tree x86_64 1.6.0-10.el7 base 46 k</code>
<code>事務概要</code>
<code>安裝 1 軟體包</code>
<code>總下載下傳量：46 k</code>
<code>安裝大小：87 k</code>
<code>Downloading packages:</code>
<code>tree-1.6.0-10.el7.x86_64.rpm | 46 kB 00:00:00 </code>
<code>Running transaction check</code>
<code>Running transaction </code><code>test</code>
<code>Transaction </code><code>test</code> <code>succeeded</code>
<code>Running transaction</code>
<code> </code><code>正在安裝 : tree-1.6.0-10.el7.x86_64 1</code><code>/1</code>
<code> </code><code>驗證中 : tree-1.6.0-10.el7.x86_64 1</code><code>/1</code>
<code>已安裝:</code>
<code> </code><code>tree.x86_64 0:1.6.0-10.el7 </code>
<code>完畢！</code>
<code>[root@openstack-01 ~]</code><code># tree</code>
<code>.</code>
<code>├── anaconda-ks.cfg</code>
<code>├── keystonerc_admin</code>
<code>├── keystonerc_demo</code>
<code>├── packstack-answers-20160505-132946.txt</code>
<code>├── packstack-answers-20160505-134047.txt</code>
<code>├── packstack-answers-20160505-152256.txt</code>
<code>├── \345\205\254\345\205\261</code>
<code>├── \346\250\241\346\235\277</code>
<code>├── \350\247\206\351\242\221</code>
<code>├── \345\233\276\347\211\207</code>
<code>├── \346\226\207\346\241\243</code>
<code>├── \344\270\213\350\275\275</code>
<code>├── \351\237\263\344\271\220</code>
<code>└── \346\241\214\351\235\242</code>
<code> </code><code>├── \346\234\252\345\221\275\345\220\215\346\226\207\344\273\266\345\244\271</code>
<code> </code><code>└── \346\234\252\345\221\275\345\220\215\346\226\207\344\273\266\345\244\271\ 2</code>
<code>10 directories, 6 files</code>
3、小結
在分析報錯資訊的時候，不能片面的根據提示資訊去做，要抓住核心，才能速度解決問題。
本文轉自 冰凍vs西瓜 51CTO部落格，原文連結：http://blog.51cto.com/molewan/1785975，如需轉載請自行聯系原作者
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