Firmware can be upgraded via TFTP from Cisco CallManager or via USB through the Cisco 7920 Configuration Utility.
Use this procedure to load the latest version firmware image for the Cisco Wireless IP Phone 7920 on Cisco CallManager 3.3(3) SR1 and later. You must install the firmware image on all Cisco CallManager servers that run TFTP service.
Note If you are using Cisco CallManager Release 3.3(2) and earlier, you must also use the phone load image helper file OS7920.txt. The 7920 device type is not supported in earlier releases of Cisco CallManager.
Sure, this is a good way to test out the new Firmware before going system wide. Once you have loaded up the new files on the TFTP Server you change this setting via Device>Phone (find specific phone) then halfway down the phone config page;
Firmware Load Information (leave blank to use default)
Phone Load Name (put the new load name here and reboot the phone so it loads this new firmware)
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.