Software Maintenance Upgrade
The Software Maintenance Upgrade (SMU) is a package that can be installed on a system to provide a patch fix or security resolution to a released image.
An SMU package is provided on a per release and per component basis and is specific to the platform.
An SMU provides a significant benefit over classic IOS software as it allows you to address the network issue quickly while reducing the time and scope of the testing required. The Cisco IOS XE platform internally validates the SMU compatibility and does not allow you to install non-compatible SMUs.
All SMUs are integrated into the subsequent Cisco IOS XE software maintenance releases. An SMU is an independent and self-sufficient package and it does not have any prerequisites or dependencies. You can choose which SMUs to install or uninstall in any order.
Starting from Cisco IOS XE Everest 16.6.1, SMUs are supported only on Extended Maintenance releases and for the full lifecycle of the underlying software release.
The following are three basic steps to install an SMU:
Addition of the SMU to the filesystem
Activation of the SMU onto the system
Committing the SMU change so it is persistent across reloads