I have installed Red Hat Enterprise Linux 6.1 server, it is registered but not subscribed. If I install using yum every time it is showing that no package available, how to resolve it?
Check, if the system is connected to any channels with
rhn-channel -l
If no output is shown, try to add a channel with
rhn-channel -a --channel=<channel-name>
Channel name may be rhel-x86_64-server-6 for example. You will need your RHN username and password for this.
I guess you'll need that subscription, because RH is a commercial distribution. You might want to try CentOS instead.
You said you've registered, but on the RH login page one can pretty clearly see the difference between registration and subscription:
Why Register with Red Hat?
Registering with Red Hat and creating a Red Hat account provides the following benefits:
Quicker online registration for upcoming events
Quicker checkout at the Red Hat store
Access to an extensive library of white papers, product evaluations and more
In addition, if you have purchased or plan to purchase a software subscription, you will have access to:
Support ticketing and reporting systems
Downloads, updates, errata, source code, solutions, articles, and groups
Another proof:
Your Red Hat subscription gives you continuous access to Red Hat software as it is created, tested, and certified by Red Hat and its partners.
With a Red Hat subscription, you have access to all supported versions in both binary and source form, including all enterprise product documentation,
security updates, and bug fixes.
Yet another proof:
The following sections assume your system was registered with Red Hat Subscription Management during installation as described in <cut>
from https://access.redhat.com/documentation/en-US/Red\_Hat\_Enterprise\_Linux/7/html/System\_Administrators_Guide/ch-yum.html