# Nerves basics ## Terminology | Term | Definition | | --------------- | --------------------------------------------------------------------------------------------------------------------- | | host | The computer on which you are editing source code, compiling, and assembling firmware | | target | The platform for which your firmware is built (for example, Raspberry Pi Zero W, Raspberry Pi 4, or Beaglebone Black) | | toolchain | The tools required to build code for the target, such as compilers, linkers, binutils, and C runtime | | system | A lean Buildroot-based Linux distribution that has been customized and cross-compiled for a particular target | | firmware bundle | A single file with the extension `.fw` that contains your compiled application and everything else needed to run on your target | | firmware image | Built from a firmware bundle. It's a raw representation of what's on the MicroSD card. These aren't used in normal development and firmware updates. | ## Nerves systems | Nerves system | MIX_TARGET | Hardware | | --- | --- | --- | | [nerves_system_rpi](https://github.com/nerves-project/nerves_system_rpi) | `rpi` | Raspberry Pi A+, B, B+ | | [nerves_system_rpi0](https://github.com/nerves-project/nerves_system_rpi0) | `rpi0` | Raspberry Pi Zero and Zero W | | [nerves_system_rpi2](https://github.com/nerves-project/nerves_system_rpi2) | `rpi2` | Raspberry Pi 2 | | [nerves_system_rpi3](https://github.com/nerves-project/nerves_system_rpi3) | `rpi3` | Raspberry Pi 3 B, B+ | | [nerves_system_rpi3a](https://github.com/nerves-project/nerves_system_rpi3a) | `rpi3a` | Raspberry Pi 3A and Zero 2 W (32-bit) | | [nerves_system_rpi0_2](https://github.com/nerves-project/nerves_system_rpi0_2) | `rpi0_2` | Raspberry Pi Zero 2 W and 3A (64-bit) | | [nerves_system_rpi4](https://github.com/nerves-project/nerves_system_rpi4) | `rpi4` | Raspberry Pi 4 | | [nerves_system_rpi5](https://github.com/nerves-project/nerves_system_rpi5) | `rpi5` | Raspberry Pi 5 | | [nerves_system_bbb](https://github.com/nerves-project/nerves_system_bbb) | `bbb` | BeagleBone Black, Green, Green Wireless, and PocketBeagle | | [nerves_system_osd32mp1](https://github.com/nerves-project/nerves_system_osd32mp1) | `osd32mp1` | OSD32MP1 | | [nerves_system_x86_64](https://github.com/nerves-project/nerves_system_x86_64) | `x86_64` | Generic x86_64 | | [nerves_system_grisp2](https://github.com/nerves-project/nerves_system_grisp2) | `grisp2` | GRiSP 2 | | [nerves_system_mangopi_mq_pro](https://github.com/nerves-project/nerves_system_mangopi_mq_pro) | `mangopi_mq_pro` | MangoPi MQ Pro | While the Nerves core team only officially supports the above hardware, the community has added support for other boards. See [Nerves Systems on hex.pm](https://hex.pm/packages?search=depends:nerves_system_br). ## Useful shell commands {: .col-2} ### Making a new firmware from scratch #### Creating a Nerves application ```bash $ mix nerves.new hello_nerves $ cd hello_nerves ``` #### Specifying Nerves target ```bash $ export MIX_TARGET= ``` #### Installing dependencies ```bash $ mix deps.get ``` #### Building firmware ```bash $ mix firmware ``` #### Creating a bootable MicroSD card ```bash $ mix burn ``` The `mix burn` command discovers any MicroSD cards on your computer. It will confirm before writing the card. ### Uploading firmware to a Nerves device over SSH ```bash $ export MIX_TARGET= $ mix upload nerves.local ``` Substitute `nerves.local` with `nerves-abcd.local` when you have multiple Nerves devices. ### Connecting to the target over SSH #### Testing the network connection ```bash $ ping nerves.local ``` #### Making the network connection ```bash $ ssh nerves.local ``` ### Connecting to the target with a serial cable #### Serial ports On boards with USB gadget support (e.g., rpi0, rpi0_2, bbb), the IEx prompt is available over a virtual serial port on the USB cable. Other boards (e.g., rpi5) require a separate USB-to-serial adapter. Serial devices show up as `/dev/tty.usbmodem*` or `/dev/ttyUSB0`. #### Using screen ```bash $ screen /dev/tty 115200 ``` Exit `screen` with CTRL+A, CTRL+\ #### Using picocom ```bash $ picocom -b 115200 /dev/tty ``` Exit `picocom` with CTRL+A, CTRL+X ### Misc #### Printing Nerves information ```bash $ mix nerves.info ``` #### Discovering Nerves devices on the local network ```bash $ mix nerves.discover ``` #### Listing Nerves artifacts cached locally ```bash $ ls ~/.nerves/artifacts ``` #### Listing Nerves downloads cached locally ```bash $ ls ~/.nerves/dl ``` > If `$XDG_DATA_HOME` is set, Nerves stores data under `$XDG_DATA_HOME/nerves/` instead of `~/.nerves`. ## Useful IEx commands {: .col-2} ### Firmware ```elixir iex> uname iex> reboot iex> Nerves.Runtime.revert iex> Nerves.Runtime.KV.get_all iex> NervesMOTD.print ``` ### Logging ```elixir iex> log_attach iex> log_detach iex> RingLogger.viewer ``` ### Linux commands ```elixir iex> cmd "ps" ``` ### Reverse search ``` text to find ``` ### Misc ```elixir iex> h Toolshed iex> hostname iex> top iex> weather iex> cat "/proc/cpuinfo" iex> hex 255 ```