category: RaspberryPi h2. Overview @cmdline.txt@ is a plain text file used by the "Raspberry Pi":https://www.raspberrypi.com to pass parameters to the kernel (i.e. the RISC OS ROM) during system boot. The file should be placed in the DOS partition of the boot SD, alongside _start.elf_ and _fixup.dat_ (for more information on these other files, see [[Software information: Raspberry Pi: Firmware]]). If it is not present, no parameters are passed. It should not be confused with [[config.txt (Raspberry Pi)|config.txt]] (which is used to supply configuration options to the bootloader). h2. Accessing cmdline.txt As stated above, cmdline.txt lives in the DOS partition of the SD card. On a standard RISC OS build using a [[Dual-format SD card]], this can be reached by double-clicking on <b>!Boot.Loader</b> (i.e. shift-doubleclick on !Boot and then double-click on the file called "Loader"). h2. Structure The important thing to remember is that cmdline.txt contains a command *line*. Only the first line of the file is read, so parameters must be space separated on the first line. For example: <pre> disable_mode_changes disable_gamma </pre> h2. Parameters At present, the following parameters are available under RISC OS. h3. disable_gamma Introduced in July 2018, @disable_gamma@ prevents use of the hardware gamma tables in BCMVideo. Use this parameter if you experience "screen blanking":https://www.riscosopen.org/forum/forums/11/topics/10346 problems while running RISC OS 5.25, 5.27 or 5.29. This parameter is not needed at 5.24/5.26/5.28, as the hardware gamma tables are disabled by default in stable releases of RISC OS. h3. disable_mode_changes Introduced in December 2016, @disable_mode_changes@ locks the screen pixel resolution to the one chosen at startup. You may want to use this parameter if you are using the "AnyMode" utility to force upscaling of lower-resolution screen modes. PLEASE NOTE: When using this parameter, you may also need to specify the appropriate @hdmi_group@ and @hdmi_mode@ settings in [[config.txt (Raspberry Pi)|config.txt]].