============================== Customizing NSH Initialization ============================== **Ways to Customize NSH Initialization**. There are three ways to customize the NSH start-up behavior. Here they are presented in order of increasing difficulty: #. You can extend the initialization logic in ``boards/arm/stm32/stm3240g-eval/src/stm32_appinit.c``. The logic there is called each time that NSH is started and is good place in particular for any device-related initialization. #. You replace the sample code at ``apps/examples/nsh/nsh_main.c`` with whatever start-up logic that you want. NSH is a library at ``apps/nshlib``. ``apps.examples/nsh`` is just a tiny, example start-up function (``CONFIG_INIT_ENTRYPOINT``\ ()) that runs immediately and illustrates how to start NSH If you want something else to run immediately then you can write your write your own custom ``CONFIG_INIT_ENTRYPOINT``\ () function and then start other tasks from your custom ``CONFIG_INIT_ENTRYPOINT``\ (). #. NSH also supports a start-up script that executed when NSH first runs. This mechanism has the advantage that the start-up script can contain any NSH commands and so can do a lot of work with very little coding. The disadvantage is that is is considerably more complex to create the start-up script. It is sufficiently complex that is deserves its own paragraph NuttShell Start up Scripts -------------------------- First of all you should look at `NSH Start-Up Script <#startupscript>`__ paragraph. Most everything you need to know can be found there. That information will be repeated and extended here for completeness. **NSH Start-Up Script**. NSH supports options to provide a start up script for NSH. The start-up script contains any command support by NSH (i.e., that you see when you enter 'nsh> help'). In general this capability is enabled with ``CONFIG_NSH_ROMFSETC=y``, but has several other related configuration options as described with the `NSH-specific configuration settings <#nshconfiguration>`__ paragraph. This capability also depends on: - ``CONFIG_DISABLE_MOUNTPOINT=n``. If mount point support is disabled, then you cannot mount *any* file systems. - ``CONFIG_FS_ROMFS`` enabled. This option enables ROMFS file system support. **Default Start-Up Behavior**. The implementation that is provided is intended to provide great flexibility for the use of Start-Up files. This paragraph will discuss the general behavior when all of the configuration options are set to the default values. In this default case, enabling ``CONFIG_NSH_ROMFSETC`` will cause NSH to behave as follows at NSH start-up time: - NSH will create a read-only RAM disk (a ROM disk), containing a tiny ROMFS file system containing the following:: `--init.d/ `-- rcS `-- rc.sysinit Where ``rcS`` is the NSH start-up script. Where ``rc.sysinit`` is the NSH system-init script. - NSH will then mount the ROMFS file system at ``/etc``, resulting in:: |--dev/ | `-- ram0 `--etc/ `--init.d/ `-- rcS `-- rc.sysinit - By default, the contents of ``rc.sysinit`` script are:: # Create a RAMDISK and mount it at /tmp mkrd -m 1 -s 512 1024 mkfatfs /dev/ram1 mount -t vfat /dev/ram1 /tmp - NSH will execute the script at ``/etc/init.d/rc.sysinit`` at system init (before the first NSH prompt). After execution of the script, the root FS will look like:: |--dev/ | |-- ram0 | `-- ram1 |--etc/ | `--init.d/ | `-- rcS | `-- rc.sysinit `--tmp/ **Example Configurations**. Here are some configurations that have ``CONFIG_NSH_ROMFSETC=y`` in the NuttX configuration file. They might provide useful examples: - ``boards/arm/stm32/hymini-stm32v/nsh2`` - ``boards/arm/dm320/ntosd-dm320/nsh`` - ``boards/sim/sim/sim/nsh`` - ``boards/sim/sim/sim/nsh2`` - ``boards/sim/sim/sim/nx`` - ``boards/sim/sim/sim/nx11`` - ``boards/sim/sim/sim/touchscreen`` In most of these cases, the configuration sets up the *default* ``/etc/init.d/rc.sysinit`` and ``/etc/init.d/rcS`` script. The default script is here: ``apps/nshlib/rc.sysinit.template`` and ``apps/nshlib/rcS.template``. (The funny values in the rc.sysinit.template like ``XXXMKRDMINORXXX`` get replaced via ``sed`` at build time). This default configuration creates a ramdisk and mounts it at ``/tmp`` as discussed above. If that default behavior is not what you want, then you can provide your own custom ``rc.sysinit`` and ``rcS`` script by defining ``CONFIG_NSH_ARCHROMFS=y`` in the configuration file. **Modifying the ROMFS Image**. The contents of the ``/etc`` directory are retained in the file ``apps/nshlib/nsh_romfsimg.h`` OR, if ``CONFIG_NSH_ARCHROMFS`` is defined, ``include/arch/board/nsh_romfsimg.h``. In order to modify the start-up behavior, there are three things to study: #. **Configuration Options.** The additional ``CONFIG_NSH_ROMFSETC`` configuration options discussed with the other `NSH-specific configuration settings <#nshconfiguration>`__. #. ``tools/mkromfsimg.sh`` **Script**. The script ``tools/mkromfsimg.sh`` creates ``nsh_romfsimg.h``. It is not automatically executed. If you want to change the configuration settings associated with creating and mounting the ``/tmp`` directory, then it will be necessary to re-generate this header file using the ``tools/mkromfsimg.sh`` script. The behavior of this script depends upon several things: #. The configuration settings then installed configuration. #. The ``genromfs`` tool(available from `http://romfs.sourceforge.net `__) or included within the NuttX buildroot toolchain. There is also a snapshot available in the NuttX tools repository `here `__. #. The ``xxd`` tool that is used to generate the C header files (xxd is a normal part of a complete Linux or Cygwin installation, usually as part of the ``vi`` package). #. The file ``apps/nshlib/rc.sysinit.template`` (OR, if ``CONFIG_NSH_ARCHROMFS`` is defined ``include/arch/board/rc.sysinit.template``. The file ``apps/nshlib/rcS.template`` (OR, if ``CONFIG_NSH_ARCHROMFS`` is defined ``include/arch/board/rcs.template``. #. ``rc.sysinit.template``. The file ``apps/nshlib/rc.sysinit.template`` contains the general form of the ``rc.sysinit`` file; configured values are plugged into this template file to produce the final ``rc.sysinit`` file. ``rcS.template``. The file ``apps/nshlib/rcS.template`` contains the general form of the ``rcS`` file; configured values are plugged into this template file to produce the final ``rcS`` file. To generate a custom ``rc.sysinit`` and ``rcS`` file a copy of ``rc.sysinit.template`` and ``rcS.template`` needs to be placed at ``tools/`` and changed according to the desired start-up behaviour. Running ``tools/mkromfsimg.h`` creates ``nsh_romfsimg.h`` which needs to be copied to ``apps/nshlib`` OR if ``CONFIG_NSH_ARCHROMFS`` is defined to ``boards////include``. ``rc.sysinit.template``. The default ``rc.sysinit.template``, ``apps/nshlib/rc.sysinit.template``, generates the standard, default ``apps/nshlib/nsh_romfsimg.h`` file. ``rcS.template``. The default ``rcS.template``, ``apps/nshlib/rcS.template``, generates the standard, default ``apps/nshlib/nsh_romfsimg.h`` file. If ``CONFIG_NSH_ARCHROMFS`` is defined in the NuttX configuration file, then a custom, board-specific ``nsh_romfsimg.h`` file residing in ``boards////include``\ will be used. NOTE when the OS is configured, ``include/arch/board`` will be linked to ``boards////include``. All of the startup-behavior is contained in ``rc.sysinit.template`` and ``rcS.template``. The role of ``mkromfsimg.sh`` script is to (1) apply the specific configuration settings to ``rc.sysinit.template`` to create the final ``rc.sysinit``, and ``rcS.template`` to create the final ``rcS``, and (2) to generate the header file ``nsh_romfsimg.h`` containing the ROMFS file system image. To do this, ``mkromfsimg.sh`` uses two tools that must be installed in your system: #. The ``genromfs`` tool that is used to generate the ROMFS file system image. #. The ``xxd`` tool that is used to create the C header file.