报错如下：

[ root@localhost ~]# yum install -y tomcat
L oaded plugins: fastestmirror
base
3.6 kB
00: 00:00
http:// 192.168.1.191/cobbler/ks_ mirror/centos7 .4-x8664/ repodata/ repomd.xmt: [Errno 12] Timeout on htt
p:// 192.168.1.191/cobbler/ks_ mirror/centos7 .4-x8664/ repodata/ repomd. xml: (28， ' Connection timed out a
fter 30001 milliseconds')
Trying other mirror
^Chttp:// 192.168.1.191/cobbler/ks mirror/centos7.4-x86 64/ repodata/ repomd. xml: [Errno 14] curL#56
"C
allback aborted"
Trying other mirror .

查看/etc/yum.repos.d/目录发现多出一个cobbler-config.repo

[ root@localhost ~]# 11 /etc/ yum. repos . d/
total 32
rw-r--r--.1 root root 1664 Aug 302017 CentOS -Base. repo
rw-r--r--.1 root root 1309 Aug 302017 CentOS CR. repo
rW-r--r--.1 root root649 Aug 302017 CentOS Debuginfo. repo
rW-r--r--.1 root root314 Aug 302017 CentOS- fas ttrack. repo 
rw-r--r--.1 root root630 Aug 302017 CentOS Media. repo
rw-r--r--.1 root root 1331 Aug 30 2017 CentOS - Sources . repo
rw-r--r--.1 root root 3830 Aug 302017 CentOS - Vault. repo
rW-r-- r--1 root root120 Aug 27 17 :50 cobbler-config. repo

rm -rf 删除该文件之后恢复正常。