Explanation
The Cisco IOS Resilient Configuration feature enables a router to secure and maintain a working copy of the
running image and configuration so that those files can withstand malicious attempts to erase the contents of
persistent storage (NVRAM and flash).
In 12.3(8)T this feature was introduced.
The following commands were introduced or modified: secure boot-config, secure boot-image, showsecure
bootset.
https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/sec_usr_cfg/configuration/15-mt/sec-usr-cfg-15-mt-book/sec-