An aspect relates to fail safe flashing techniques for a management device of a computer system. A non-volatile memory of the management device stores a current firmware, an actual critical information and a backup critical information, which is rewritable in a booting mode and read-only in a flash mode. A flasher module is launched to operate the management device in the flash mode. The actual critical information is copied to a volatile memory and erased in the non-volatile memory. A replacement firmware is used to upgrade the current firmware. The actual critical information is mixed and matched with a new critical information. A user input is requested to write the mixed and matched critical information back to the non-volatile memory as the actual critical information. When the user input is not received after a first predetermined time period, the mixed and matched critical information is automatically written back.