...
http://ftp.sjtu.edu.cn/centos/7.6.1810/os/x86_64/Packages/ftp-0.17-67.el7.x86_64.rpm: [Errno 14] HTTP Error 404 - Not Found
Trying other mirror
1.清理无效的软件源
$ yum clean all
2.缓存软件
$ yum makecache
...
http://ftp.sjtu.edu.cn/centos/7.6.1810/os/x86_64/Packages/ftp-0.17-67.el7.x86_64.rpm: [Errno 14] HTTP Error 404 - Not Found
Trying other mirror
1.清理无效的软件源
$ yum clean all
2.缓存软件
$ yum makecache