添加Epel源:

方法一：
sudo yum install epel-release -y
方法二：
sudo yum install https://dl.fedoraproject.org/pub/epel/epel-release-latest-8.noarch.rpm
sudo yum install https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm
sudo yum install https://dl.fedoraproject.org/pub/epel/epel-release-latest-6.noarch.rpm
注：
安装后执行yum install soft-package -y报
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
Error: Cannot retrieve metalink for repository: epel. Please verify its path and try again
或
Peer cert cannot be verified or peer cert invalid
解决方法：
添加 "sslverify=false" 到 /etc/yum.conf
添加Elrepo源：

sudo rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org
sudo yum install https://www.elrepo.org/elrepo-release-8.0-2.el8.elrepo.noarch.rpm
sudo yum install https://www.elrepo.org/elrepo-release-7.0-4.el7.elrepo.noarch.rpm
sudo yum install https://www.elrepo.org/elrepo-release-6-9.el6.elrepo.noarch.rpm
添加Rpmforge源：

sudo yum install http://repository.it4i.cz/mirrors/repoforge/redhat/el7/en/x86_64/rpmforge/RPMS/rpmforge-release-0.5.3-1.el7.rf.x86_64.rpm
sudo yum install http://repository.it4i.cz/mirrors/repoforge/redhat/el6/en/x86_64/rpmforge/RPMS/rpmforge-release-0.5.3-1.el6.rf.x86_64.rpm
添加Remi源：

sudo yum install http://rpms.remirepo.net/enterprise/remi-release-8.rpm
sudo yum install http://rpms.famillecollet.com/enterprise/remi-release-7.rpm
sudo yum install http://rpms.famillecollet.com/enterprise/remi-release-6.rpm
添加IUS repo源：

CentOS

sudo yum install https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm
sudo yum install https://dl.fedoraproject.org/pub/epel/epel-release-latest-6.noarch.rpm
sudo yum install https://centos7.iuscommunity.org/ius-release.rpm
sudo yum install https://centos6.iuscommunity.org/ius-release.rpm

RHEL

sudo yum install https://rhel7.iuscommunity.org/ius-release.rpm
sudo yum install https://rhel6.iuscommunity.org/ius-release.rpm
添加Webtatic源：

sudo yum install http://rpms.famillecollet.com/enterprise/remi-release-7.rpm
sudo yum install http://repo.webtatic.com/yum/el7/webtatic-release.rpm
sudo yum install http://rpms.famillecollet.com/enterprise/remi-release-6.rpm
sudo yum install http://repo.webtatic.com/yum/el6/latest.rpm
添加nux-dextop源：

sudo rpm --import http://li.nux.ro/download/nux/RPM-GPG-KEY-nux.ro
sudo rpm -Uvh http://li.nux.ro/download/nux/dextop/el7/x86_64/nux-dextop-release-0-2.el7.nux.noarch.rpm
sudo rpm -Uvh http://li.nux.ro/download/nux/dextop/el6/x86_64/nux-dextop-release-0-2.el6.nux.noarch.rpm
aliyun-repo

http://mirrors.aliyun.com/repo/

search it

sudo yum search htop sysstat

get more info, if found

sudo yum info htop sysstat

install it

sudo yum install htop sysstat