What is required to restore functionality to a critical server that crashed after applying new patches?

Restoring functionality to a critical server that crashed after applying new patches typically involves using a backout plan. A backout plan is a predefined procedure that is initiated to revert a system to its previous stable state before the changes were made, in this case, before the new patches were applied. Implementing this plan helps ensure that the server can resume normal operations while minimizing downtime and data loss.

Using a backout plan is crucial in situations where patches cause stability issues or other problems that affect the server's functionality. By following this procedure, administrators can effectively manage the risks associated with patching, which sometimes leads to unexpected issues due to incompatibilities or bugs in the patches.

The other approaches, like rebooting the server or reapplying the patches, may not effectively address the underlying problem caused by the patches. In some cases, they might even exacerbate the situation. Installing additional patches could lead to further complications if the initial patches are unstable.

Thus, a backout plan is the essential and systematic approach to restore the server’s functionality after an unsuccessful patch application.