Mac + DockerでCentOSを立ち上げたらyumが全く使えなかった話

CentOSでNodeを動かしたくてMac + DockerでCentosを立ち上げていたときの話...

Loaded plugins: fastestmirror, ovl
  Loading mirror speeds from cached hostfile
  
  
   One of the configured repositories failed (Unknown),
   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=<repoid> ...
  
       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 <repoid>
          or
              subscription-manager repos --disable=<repoid>
  
       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=<repoid>.skip_if_unavailable=true
  
  Cannot find a valid baseurl for repo: base/$releasever/x86_64
  

yum系のコマンドを使うと上記のようなエラーが出てしまってどうすることもできない。

vi /etc/yum.repos.d/CentOS-Base.repo
  

のmirrorlistをコメントアウトしてbaseurlにしてもだめ スタックオーバーフローでこんな記述を発見 https://stackoverflow.com/questions/42131460/centos-yum-fails-installing-anything-or-updating-system なんやら、URLに埋め込まれてる$releaseverがうまく機能してないって話らしい ただ、この手順をやろうとするとwgetが必要になりwgetが使えないマンだったので yum install wget はい、使えるわけがない 要は$releaseverが死んでるんだからそこの部分を決めうちにしてしまえば良いんじゃない?と思って

baseurl=http://mirror.centos.org/centos/$releasever/updates/$basearch/
  

の部分を

baseurl=http://mirror.centos.org/centos/7/updates/$basearch/
  

に全部変更 そしたら無事動きました!!!! dockerから最新のCentOS引っ張ってきてるはずなんだけどな?