Responding to Subscription Notifications
The CentOS Subscription Manager provides a series of log and UI messages that indicate any changes to the valid certificates of any installed products for a system. In the Subscription Manager GUI, the status of the system entitlements is color-coded, where green means all products are fully subscribed, yellow means that some products may not be subscribed but updates are still in effect, and red means that updates are disabled.

Figure 14.18. Color-Coded Status Views
The command-line tools also indicate that status of the machine. The green-yellow-red codes translate to text status messages of subscribed, partially subscribed, and expired/not subscribed, respectively.
[root@server ~]# subscription-manager list
+-------------------------------------------+
Installed Product Status
+-------------------------------------------+
ProductName: Community Enterprise Linux Server
Status: Not Subscribed
Expires:
SerialNumber:
ContractNumber:
AccountNumber:
Whenever there is a warning about subscription changes, a small icon appears in the top menu bar, similar to a fuel gauge.

Figure 14.19. Subscription Notification Icon
As any installed product nears the expiration date of the subscription, the Subscription Manager daemon will issue a warning. A similar message is given when the system has products without a valid certificate, meaning either the system is not subscribed to a subscription that entitles that product or the product is installed past the expiration of the subscription. Clicking the Manage My Subscriptions... button in the subscription notification window opens the CentOS Subscription Manager GUI to view and update subscriptions.

Figure 14.20. Subscription Warning Message
When the Subscription Manager UI opens, whether it was opened through a notification or just opened normally, there is a box in the upper left corner that shows the number of products that lack a valid certificate. The easiest way to allocate subscriptions which match invalidated products is to click the Update Certificates button.

Figure 14.21. Update Certificates Button
The Subscription Assistant pop-up window shows a targeted list of available subscriptions that apply to the specific products that do not have valid certificates (assuming subscriptions are available).

Figure 14.22. Subscription Assistant
Alternatively, you can respond to entitlements notifications by managing subscriptions generally:
- The entitlements certificate can be updated or a new one can be added ("Updating Entitlements Certificates").
- The system can be subscribed to another subscription that contains the product ("Handling Subscriptions").