Well it is not so easy to install a subscription-manager without an active yum repo. but there is a way
outside container (must be registered with RHN already!):
```
yum install -y yum-utils
cd /opt/gluu-server-2.4.4/root
yumdownloader --archlist=x86_64 python-rhsm-certificates gobject-introspection pygobject3-base python-dateutil python-rhsm subscription-manager
cp /etc/pki/consumer/key.pem /opt/gluu-server-2.4.4/etc/pki/
/usr/sbin/gluu-serverd-2.4.4 login
```
(because of login, inside container)
```
rpm -ivh python-rhsm-certificates gobject-introspection pygobject3-base python-dateutil python-rhsm subscription-manager
subscription-manager register
subscription-manager attach
```
if you need a proxy to access the internet, make sure you have a valid https_proxy pointing to your proxy.