Is subscription-manager available for CentOS?
Solution 1:
Yes, the subscription-manager tool is Red Hat-specific, allowing you to manage Red Hat subscriptions. Since CentOS doesn't have subscriptions, CentOS 6 omitted this tool.
CentOS 7 now includes subscription-manager, which you can use with Red Hat Satellite or its open source versions Spacewalk or Foreman/Katello.
Solution 2:
subscription-manager for CentOS 6 is available
wget -O /etc/yum.repos.d/epel-rhsm.repo http://repos.fedorapeople.org/repos/candlepin/subscription-manager/epel-subscription-manager.repo
yum install subscription-manager -y