[root@192Python-3.6.6]#yum m-y instalt zlib-devel bzip2-devel openssi-devel ncurses-devel sqlite-devel readline-devel tk-devel gcc make gdb
m-devel db4-devel libpcap-devel xz-devel libffi-devel
Loadedplugins:fastestmirror，langpacks
Loading mirror speedsfrom cached hostfile
Couldnotretrievemirrorlisthttp://mirrorlist.centos.org/?release=7&arch=x8664&repo=os&infra=stockerrorwas
14:curl#6-"Couldnotresolvehost:mirrorlist.centos.org;Unknownerror"
One of the configuredrepositoriesfailed（Unknown），
andyumdoesnthaveenough cacheddatato continue.Atthispointtheonly
safe thing yum can do is fail.There are a fewways to work "fix" this:
1.Contact theupstreamfor therepository and getthem tofixtheproblem
2.Reconfigurethebaseurl/etc.fortherepository，topoint toaworking
upstream.Thisismost often useful ifyouareusinganewer
distributionreleasethanis supportedby therepository（andthe
packages for the previous distribution release still work）.
3.Run the command with the repository temporarily disabled
4.Disable the repository permanently，soyum 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-managerrepos--disable=<repoid
5.Configure the failing repository to be skipped，if itis unavailable.
Note thatyumwiLl try to contact therepo.whenitrunsmostcommands，
So will have to try and fail each time（and thus.yum will be be much
slower）.If itis a very temporary problem though，this is often a nice
compromise CSDN@春晖饶阳
我能ping外网还需要检查什么，或者是因为什么原因
