Balena.io layers for Yocto

Description

This repository enables building balenaOS for various devices.

Layers Structure

• meta-balena-common : layer which contains common recipes for all our supported platforms.
• meta-balena-* : layers which contain recipes specific to yocto versions.
• other files : README, COPYING, etc.

Dependencies

• http://www.yoctoproject.org/docs/latest/yocto-project-qs/yocto-project-qs.html#packages
• docker
• jq

Versioning

meta-balena version is kept in DISTRO_VERSION variable. balena-<board> version is kept in the file called VERSION located in the root of the balena-<board> repository and read in the build as variable HOSTOS_VERSION.

• The version of meta-balena is in the format is 3 numbers separated by a dot. The patch number can have a beta label. e.g. 1.2.3, 1.2.3-beta1, 2.0.0-beta1.
• The version of balena-<board> is constructed by appending to the meta-balena version a rev label. This will have the semantics of a board revision which adapts a specific meta-balena version for a targeted board. For example a meta-balena 1.2.3 can go through 3 board revisions at the end of which the final version will be 1.2.3+rev3 .
• The first balena-board release based on a specific meta-balena release X.Y.Z, will be X.Y.Z+rev1 . Example: the first balena-board version based on meta-balena 1.2.3 will be 1.2.3+rev1 .
• When updating meta-balena version in balena-board, the revision will reset to 1. Ex: 1.2.3+rev4 will be updated to 1.2.4+rev1 .
• Note that the final OS version is NOT based on semver specification so parsing of such a version needs to be handled in a custom way.
• e.g. For meta-balena release 1.2.3 there can be balena-<board> releases 1.2.3+revX.
• e.g. For meta-balena release 2.0.0-beta0 there can be balena-<board> releases 2.0.0-beta0+revX.

We define host OS version as the balena-<board> version and we use this version as HOSTOS_VERSION.

Build flags

Before bitbake-ing with meta-balena support, a few flags can be changed in the conf/local.conf from the build directory. Editing of local.conf is to be done after source-ing. See below for explanation on such build flags.

Development Images

The DEVELOPMENT_IMAGE variable gets injected into DISTRO_FEATURES. If DEVELOPMENT_IMAGE = "1" then 'development-image' distro feature is added. Based on this, recipes can decide what development specific changes are needed. By default DEVELOPMENT_IMAGE = "0" which corresponds to a normal (non-development) build (development-image won't be appended to DISTRO_FEATURE). If user wants a build which creates development images (to use the serial console for example), DEVELOPMENT_IMAGE = "1" needs to be added to local.conf.

To make it short:

• If DEVELOPMENT_IMAGE is not present in your local.conf or it is not "1" : Non-development images will be generated (default behavior)
• If DEVELOPMENT_IMAGE is defined local.conf and its value is "1" : Development images will be generated

Generation of host OS update bundles

In order to generate update balena host OS bundles, edit the build's local.conf adding:

RESINHUP = "yes"

Configure custom network manager

By default balena uses NetworkManager on host OS to provide connectivity. If you want to change and use other providers, list your packages using NETWORK_MANAGER_PACKAGES. You can add this variable to local.conf. Here is an example:

NETWORK_MANAGER_PACKAGES = "mynetworkmanager mynetworkmanager-client"

Customizing splash

We configure all of our initial images to produce a balena logo at boot, shutdown or reboot. But we encourage any user to go and replace that logo with their own. All you have to do is replace the splash/balena-logo.png file that you will find in the first partition of our images (boot partition) with your own image. NOTE: As it currently stands plymouth expects the image to be named balena-logo.png. In older releases this file was called resin-logo.png.

Docker storage driver

By default the build system will set all the bits needed for the docker to be able to use the aufs storage driver. This can be changed by defining BALENA_STORAGE in your local.conf. It supports aufs and overlay2.

The OS

SSH and Avahi services

The OS runs SSH (openSSH) on port 22222. Running this service takes advantage of the socket activation systemd feature so the SSH daemon will only run when there is a SSH connection to the device saving idle resources in this way. In order to connect to a device, one can use it's IP when known or resolve the hostname over mDNS as its hostname is advertised over network using an avahi service. When the latter is used, configuration of the client is needed (see for example https://wiki.archlinux.org/index.php/Avahi#Hostname_resolution).

Time in the OS

We currently have three time sources:

• build time - stored in /etc/timestamp and generated by the build system when the image is generated
• network time - managed by chronyd
• RTC time when available

Early in the boot process, the OS will start three services associated with the sources listed above, which manage the system clock.

The first one is timeinit-rtc. This service, when a RTC is available (/etc/rtc) will update the system clock using the value read from the RTC. If there is no RTC available, the service will not do anything. The second service is timeinit-timestamp which reads the build timestamp and updates the system clock if the timestamp is after the current system clock. The third service is chronyd.service which is responsible of managing the time afterwards over NTP.

The order of the services is as stated above and provides a robust time initialization at boot in both cases where RTC is or not available.

Rollback framework

Check docs/rollbacks.md for the rollback documentation

Devices support

WiFi Adapters

We currently tested and provide explicit support for the following WiFi adapters:

• bcm43143 based adapters
  • Example: Official RPI WiFi adapter link

Modems

We currently test as part of our release process and provide explicit support for the following modems:

• USB modems (tested on Raspberry Pi 3, Balena Fin, Intel NUC and Nvidia TX2)
  • Huawei MS2131i-8
  • Huawei MS2372
• mPCI modems (tested on Balena Fin and Nvidia TX2 Spacely carrier)
  • Huawei ME909s-120
  • Quectel EC20
  • SIM7600E

Recommended WiFi USB dongle

• Panda N600 Dual-Band (2.4 GHz + 5 GHz) Wireless-N USB Adapter This USB dongle is based on the Ralink RT5572 chipset and is supported by the generic rt2800usb driver. Tests have been done on the PAU09 model of the Panda N600 Dual-Band USB Adapter and having the firmware version 0.36 from firmware file rt2870.bin

How to fix various build errors

• Supervisor fails with a log similar to:

Step 3 : RUN chmod 700 /entry.sh
---> Running in 445fe69866f9
operation not supported

This is probably because of a docker bug where, if you update kernel and don't reboot, docker gets confused. The fix is to reboot your system. More info: http://stackoverflow.com/questions/29546388/getting-an-operation-not-supported-error-when-trying-to-run-something-while-bu

config.json

The behavior of balenaOS can be configured by setting the following keys in the config.json file in the boot partition. This configuration file is also used by the supervisor.

hostname

(string) The configured hostname of the device, otherwise the device UUID is used.

persistentLogging

(boolean) Enable or disable persistent logging on the device - defaults to false.

country

(string) Two-letter country code for the country in which the device is operating. This is used for setting the WiFi regulatory domain, and you should check the WiFi device driver for a list of supported country codes.

ntpServers

(string) A space-separated list of NTP servers to use for time synchronization. Defaults to resinio.pool.ntp.org servers:

• 0.resinio.pool.ntp.org
• 1.resinio.pool.ntp.org
• 2.resinio.pool.ntp.org
• 3.resinio.pool.ntp.org

dnsServers

(string) A space-separated list of preferred DNS servers to use for name resolution.

• When dnsServers is not defined, or empty, Google's DNS server (8.8.8.8) is added to the list of DNS servers obtained via DHCP or statically configured in a NetworkManager connection profile.
• When dnsServers is "null" (a string), Google's DNS server (8.8.8.8) will NOT be added as described above.
• When dnsServers is defined and not "null", the listed servers will be added to the list of servers obtained via DHCP or statically configured via a NetworkManager connection profile.

balenaRootCA

(string) A base64-encoded CA certificate if trusted and required for connection.

os

An object containing settings that customize the host OS at runtime.

network

wifi

An object that defines the configuration related to Wi-Fi.

• "randomMacAddressScan" (boolean) Configures MAC address randomization of a Wi-Fi device during scanning

The following example disables MAC address randomization of Wi-Fi device during scanning:

"os": {
 "network" : {
  "wifi": {
    "randomMacAddressScan": false
  }
 }
}

connectivity

An object that defines configuration related to networking connectivity checks. This feature builds on NetworkManager's connectivity check, which is further documented in the connectivity section here.

• "uri" (string) Value of the url to query for connectivity checks. Defaults to $API_ENDPOINT/connectivity-check.
• "interval" (string) Interval between connectivity checks in seconds. Defaults to 3600. To disable the connectivity checks set the interval to "0".
• "response" (string). If set controls what body content is checked for when requesting the URI. If it is an empty value, the HTTP server is expected to answer with status code 204 or send no data.

The following example configures the connectivity check by passing the balenaCloud connectivity endpoint with a 5-minute interval.

"os": {
 "network" : {
  "connectivity": {
    "uri" : "https://api.balena-cloud.com/connectivity-check",
    "interval" : "300"
  }
 }
}

udevRules

An object containing one or more custom udev rules as key:value pairs.

To turn a rule into a format that can be easily added to config.json, use the following command:

cat rulefilename | jq -sR .

For example:

cat 64.rules | jq -sR .
"ACTION!=\"add|change\", GOTO=\"modeswitch_rules_end\"\nKERNEL==\"ttyACM*\", ATTRS{idVendor}==\"1546\", ATTRS{idProduct}==\"1146\", TAG+=\"systemd\", ENV{SYSTEMD_WANTS}=\"[email protected]'%E{DEVNAME}'.service\"\nLBEL=\"modeswitch_rules_end\"\n"

The following example contains two custom udev rules that will create /etc/udev/rules.d/56.rules and /etc/udev/rules.d/64.rules. The first time rules are added, or when they are modified, udevd will reload the rules and re-trigger.

"os": {
 "udevRules": {
  "56": "ENV{ID_FS_LABEL_ENC}==\"resin-root*\", IMPORT{program}=\"resin_update_state_probe $devnode\", SYMLINK+=\"disk/by-state/$env{BALENA_UPDATE_STATE}\"",
  "64" : "ACTION!=\"add|change\", GOTO=\"modeswitch_rules_end\"\nKERNEL==\"ttyACM*\", ATTRS{idVendor}==\"1546\", ATTRS{idProduct}==\"1146\", TAG+=\"systemd\", ENV{SYSTEMD_WANTS}=\"[email protected]'%E{DEVNAME}'.service\"\nLBEL=\"modeswitch_rules_end\"\n"
 }
}

sshKeys

(Array) An array of strings containing a list of public SSH keys that will be used by the SSH server for authentication.

"os": {
 "sshKeys": [
  "ssh-rsa AAAAB3Nza...M2JB [email protected]",
  "ssh-rsa AAAAB3Nza...nFTQ [email protected]"
 ]
}

Yocto version support

The following Yocto versions are supported:

• Thud (2.6)
• TESTED
• Sumo (2.5)
• TESTED
• Rocko (2.4)
• TESTED
• Pyro (2.3)
• TESTED