Occasionally, we may find there was no CLI command 'installed-systems' to perform the upgrade in Management Center as given the Upgrade/Downgrade Guide.
https://origin-symwisedownload.symantec.com/resources/webguides/managementcenter/1.8.1.1/ManagementCenter.htm#ConfigurationManagementGuide/9_Troubleshoot/upgrade_downgrade.htm%3FTocPath%3DAdministrate%2520Management%2520Center%7C_____2
When the failover mode is enabled, the system forbids the attempt to modify system images.
The solution is to first disable the failover mode then reconfigure the failover after the upgrade is completed.
Management Center# failover view
Status:
Primary*: 10.169.102.53
Secondary: 10.169.100.104
Last status update 3 second(s) ago
(*) this Management Center
Management Center# failover disable
Failover:
Status:
Primary*: 10.169.102.53
Secondary: 10.169.100.104
Last status update 0 second(s) ago
(*) this Management Center
Warning: Failover data replication is in progress. Disabling failover will stop all replication between primary and secondary nodes. Are you sure you want to disable failover? [y/N] Y
Failover:
Status: Disabled
Management Center# ?
backup Create, view and restore backups
disable Turn off privileged commands
exit Exit command line interface
failover Configure failover settings
help (or ?) Display this help
http-proxy Configure Explicit HTTP Proxy settings
installed-systems Upgrade and manage installed systems <<<
license Install and update the Management Center license
pcap Packet capturing utility
ping Ping utility