This system is not registered with an entitlement server. You can use subscription-manager to register.

Problem:

Trying to install/update/search packages using yum fails:

[root@app1 mari_scripts]# yum whatprovides clang
Loaded plugins: amazon-id, product-id, search-
              : disabled-repos, subscription-manager,
              : versionlock
This system is not registered with an entitlement server. You can use subscription-manager to register.

Excluding 1 update due to versionlock (use "yum versionlock status" to show it)
No matches found

Actually, it is still searching for the package, but the messages, in the beginning, are frustrating. So let’s just solve it.

I tried to register the system, but here also did a mistake, I have indicated the email address in the username:

[root@app1 mari_scripts]# subscription-manager register
Registering to: subscription.rhsm.redhat.com:443/subscription
Username: <my RHEL username, email address>
Password:
HTTP error (401 - Unauthorized): Invalid username or password. To create a login, please visit https://www.redhat.com/wapps/ugc/register.html

I was able to login through browser but could not register the system with it.

Solution:

After searching a lot and losing my time, I came accross one thread where the person was saying that account id should be used instead of email address. By the way, later found out the the RHEL also was mentioning that in one of its articles:

“Please use your Login ID/User ID instead of your Email Address to register your RHEL machine.”

So go to you account settings from browser and see what is your Login name, register the system with it:

[root@app1 mari_scripts]# subscription-manager register
Registering to: subscription.rhsm.redhat.com:443/subscription
Username: <myloginnamegoeshere>
Password:
The system has been registered with ID: 22328e0c-f672-4489-939b-529a9d2875a1
The registered system name is: app1.mycompany.mydomain