For backup, using a command like ps2fpkg -b to save the current firmware to a file.
I should also check if the tool requires administrator privileges on Windows, or sudo in Linux.
The title says it's a long guide, so I need to cover all aspects of the tool. Let me start by recalling what I know about PS2 modding. There are tools for modding the PlayStation 2, especially for homebrew or flash memories. Maybe ps2fpkg is a firmware flasher or a package manager for PS2 flash cards like MemoryCard Pro or others.