nerves_pack v0.3.2 NervesPack View Source

Nerves Pack

Hex version CircleCI

This library is a compilation of dependencies and default configuration for getting a Nerves project up and running with minimal work. Essentially nerves_init_gadget 2.0 to work with new networking libraries and practices.

When added to your project, the following services are enabled by default:

  • Networking - Utilizes VintageNet
  • mDNS - via MdnsLite. Supports nerves.local and the default hostname (i.e. nerves-1234.local) This is also configurable to other hostnames as well.
  • SSH - Includes SSH access, firmware updates over SSH, and SFTP

Installation

def deps do
  [
    {:nerves_pack, "~> 0.1.0"}
  ]
end

This will start NervesPack and all its services with your application. However, since it controls the networking and SSH interface, it is recommended to use it with shoehorn to start it up separately so you still have access to your device in the event that the main application fails. This can be done by adding to your config.exs

config :shoehorn,
  init: [:nerves_runtime, :nerves_pack],
  app: Mix.Project.config()[:app]

SSH port

By default, nerves_pack will start an IEx console on port 22, this can be overridden by specifying :ssh_port in the config. The SFTP subsystem is also enabled so that you can transfer files back and forth as well. To disable this feature, set :ssh_port to nil. This console will use the same ssh public keys as those configured for :nerves_firmware_ssh (see the docs for how to configure your keys). Usernames are ignored.

config :nerves_pack, ssh_port: 2222

Connect by running:

ssh nerves.local

To exit the SSH session, type exit or type the ssh escape sequence ~. . (See the ssh man page for other escape sequences). Typing Ctrl+D or logoff at the IEx prompt to exit the session won't work.

Erlang distribution

nerves_pack does not start Erlang distribution. Distribution is not hard to enable, but it requires some thought on node naming and security.

Erlang distribution requires that the hostname part of the device's node name be reachable from the computer that's trying to connect. Options include IP addresses, DNS names, mDNS names or names that you put in your /etc/hosts file. Many Nerves users use mDNS names for simplicity, but they have limitations. You may need to adjust the following script based on your environment.

The Nerves project generator configures mdns_lite to advertise two hostnames: nerves.local and nerves-1234.local. The latter one is based on the serial number of the device. If you only have one Nerves device on the network, use nerves.local. If you have many devices, you'll have to figure out the name with the serial number. This can be done by using a mDNS discovery program or by logging into a device via a serial console and typing hostname at the IEx prompt.

The following uses nerves.local, but substitute for the name that you want. Run this by ssh'ing into your Nerves device.

iex> System.cmd("epmd", ["-daemon"])
{"", 0}
iex> Node.start(:"nerves@nerves.local")
{:ok, #PID<0.26318.2>}
iex(nerves@nerves.local)> Node.set_cookie(:my_secret_cookie)
true

For a programmatic implementation, see :inet.gethostname/0 for constructing a device-specific node name.

Now that Erlang distribution is running, try to connect to the device on your computer.

$ iex --name me@0.0.0.0 --cookie my_secret_cookie --remsh nerves@nerves.local
Erlang/OTP 22 [erts-10.6.4] [source] [64-bit] [smp:32:32] [ds:32:32:10]
[async-threads:1] [hipe]

Interactive Elixir (1.9.4) - press Ctrl+C to exit (type h() ENTER for help)
iex(nerves@nerves.local)1> use Toolshed
Toolshed imported. Run h(Toolshed) for more info
:ok
iex(nerves@nerves.local)2> cat "/proc/cpuinfo"
processor       : 0
model name      : ARMv6-compatible processor rev 7 (v6l)
BogoMIPS        : 697.95
Features        : half thumb fastmult vfp edsp java tls
CPU implementer : 0x41
CPU architecture: 7
CPU variant     : 0x0
CPU part        : 0xb76
CPU revision    : 7

Hardware        : BCM2835
Revision        : 9000c1
Serial          : 00000000b27aa712
Model           : Raspberry Pi Zero W Rev 1.1

iex(nerves@nerves.local)6>

Optional WiFi wizard setup

When and how to start the WiFi wizard is generally very dependent on your use-case so it's recommended that you implement the startup logic on your own.

See the vintage_net_wizard docs for more information on use and configuration.