yum install is an essential artifact Linux system, just not too convenient. But the new system is generally not yum comes with tools, you need to manually install it.
Environment: centos7
Create a directory to save the yum install package
mkdir install
Into the folder and enter the command
wget http://yum.baseurl.org/download/3.2/yum-3.2.28.tar.gz
Decompression
tar -xvf yum-3.2.28.tar.gz
Focus: After extracting the first not in a hurry to install, create a yum-conf file manually, or file not found error will be reported yum.cli: Config Error: Error accessing file for config file: /// etc /
touch /etc/yum.conf
Enter yum directory, the installation script
cd yum-3.2.28
./yummain.py install yum
Period will be prompted to install the new version, y press Enter
Successful installation!
Upgrade to the new version will not have the check update and clean up, and go directly to use it.