Generic x86_64 System

This is the base Nerves System configuration for a generic x86_64 system that can be run with Qemu. It can be used as a base for real x86_64 systems, but it probably will require some work.

Feature	Description
CPU	Intel
Memory	512 MB+ DRAM
Storage	Hard disk/SSD/etc. (/dev/sda)
Linux kernel	6.6
IEx terminal	Virtual serial - ttyS0
Hardware I/O	None
Ethernet	Yes

Using

The most common way of using this Nerves System is create a project with mix nerves.new and to export MIX_TARGET=x86_64. See the Getting started guide for more information.

If you need custom modifications to this system for your device, clone this repository and update as described in Making custom systems

Running in qemu

It's possible to run Nerves projects built with this system in Qemu with some work. If you create a Nerves projects with the nerves_system_x86_64 dependency, here are the steps:

Create firmware like normal:

export MIX_TARGET=x86_64
mix deps.get
mix firmware

Create the disk image (virtual MicroSD/SD/eMMC):

qemu-img create -f raw disk.img 1G

Use fwup to write the image for the first time:

# Substitute the .fw file based on your project
fwup -d disk.img _build/x86_64_dev/nerves/images/circuits_quickstart.fw

Run qemu:

qemu-system-x86_64 -drive file=disk.img,if=virtio,format=raw -net nic,model=virtio -net user,hostfwd=tcp::10022-:22 -nographic -serial mon:stdio -m 1024

You should eventually get an IEx prompt. The first boot takes longer since the application data partition will be formatted. Run poweroff at the IEx prompt to exit out of Qemu or if you're having trouble, run killall qemu-system-x86_64 in another shell window.

You can ssh into the system by using port 10022. Try ssh -p 10022 localhost. It's possible to run an "over-the-air" firmware update also using ssh by running the following:

mix firmware.gen.script # create the upload.sh script
SSH_OPTIONS="-p 10022" ./upload.sh localhost

Root disk naming

If you have multiple SSDs, or other devices connected, it's possible that Linux will enumerate those devices in a nondeterministic order. This can be mitigated by using udev to populate the /dev/disks/by-* directories, but even this can be inconvenient when you just want to refer to the drive that provides the root filesystem. To address this, erlinit creates /dev/rootdisk0, /dev/rootdisk0p1, etc. and symlinks them to the expected devices. For example, if your root file system is on /dev/mmcblk0p1, you'll get a symlink from /dev/rootdisk0p1 to /dev/mmcblk0p1 and the whole disk will be /dev/rootdisk0. Similarly, if the root filesystem is on /dev/sdb1, you'd still get /dev/rootdisk0p1 and /dev/rootdisk0 and they'd by symlinked to /dev/sdb1 and /dev/sdb respectively.

Provisioning devices

This system supports storing provisioning information in a small key-value store outside of any filesystem. Provisioning is an optional step and reasonable defaults are provided if this is missing.

Provisioning information can be queried using the Nerves.Runtime KV store's Nerves.Runtime.KV.get/1 function.

Keys used by this system are:

Key	Example Value	Description
nerves_serial_number	"12345678"	By default, this string is used to create unique hostnames and Erlang node names. If unset, it defaults to part of the Ethernet adapter's MAC address.

The normal procedure would be to set these keys once in manufacturing or before deployment and then leave them alone.

For example, to provision a serial number on a running device, run the following and reboot:

iex> cmd("fw_setenv nerves_serial_number 12345678")

This system supports setting the serial number offline. To do this, set the NERVES_SERIAL_NUMBER environment variable when burning the firmware. If you're programming MicroSD cards using fwup, the commandline is:

sudo NERVES_SERIAL_NUMBER=12345678 fwup path_to_firmware.fw

Serial numbers are stored on the MicroSD card so if the MicroSD card is replaced, the serial number will need to be reprogrammed. The numbers are stored in a U-boot environment block. This is a special region that is separate from the application partition so reformatting the application partition will not lose the serial number or any other data stored in this block.

Additional key value pairs can be provisioned by overriding the default provisioning.conf file location by setting the environment variable NERVES_PROVISIONING=/path/to/provisioning.conf. The default provisioning.conf will set the nerves_serial_number, if you override the location to this file, you will be responsible for setting this yourself.