Today need to use rhel7 to test opencv. When I wanted to install opencv, yum suddenly became unavailable.

prompt:

bash: yum:command not found

I found the following methods on the Internet, and the pro-test is effective (I modified the article a little bit based on my own testing experience).

Steps
The first step:
Download the following RPM package
Python-iniparse-0.4-9.el7.noarch.rpm
yum- metadata-parser-1.1.4-10.el7.x86_64.rpm
yum-3.4.3-161.el7.centos.noarch.rpm
yum-plugin-fastestmirror-1.1.31-40.el7.noarch.rpm After the
download is complete , Use the rpm command to install, as follows:
rpm -ivh –force –nodeps python-iniparse-0.4-9.el7.noarch.rpm
rpm -ivh –force –nodeps yum-metadata-parser-1.1.4- 10.el7.x86_64.rpm
rpm -ivh –force –nodeps yum-3.4.3-161.el7.centos.noarch.rpm
rpm -ivh –force –nodeps yum-plugin-fastestmirror-1.1.31- 40.el7.noarch.rpm
needs to be noted when installing here, be sure to add –force –nodeps, otherwise it will report an error and cannot be installed

At this point, but the following error still appears when I enter the yum command:

Step 2:
Download yum-3.4.3.tar.gz and perform the following steps
wget http://yum.baseurl.org/download/3.4/yum-3.4.3.tar.gz
tar -zxvf yum-3.4.3 .tar.gz
#Unzip and enter the yum-3.4.3 directory./yummain.py     update