Targets Overview

Perhaps the most important goal of a FoundriesFactory is to deliver immutable software updates to devices. This is achieved by using the The Update Framework (TUF). The central piece to TUF is the notion of a Target. A Target defines a cryptographically verifiable description of the software a device should run. A simplified example could be:

"raspberrypi3-64-lmp-42" : {
   "hashes" : {"sha256" : "0xdeadbeef"},
   "custom" : {
     "version" : "42"
     "docker_compose_apps" : {
       "shellhttpd" : {
         "uri" : ""
     "hardwareIds" : ["raspberrypi3-64"],
     "tags" : ["master"],

This Target specifies some important bits of information:

  • This is build 42
  • The immutable OSTree hash of the base image is 0xdeadbeef
  • The Compose App, shellhttpd, is part of the Target.

The Target is the goal. Developers push changes to Git in hopes of building a Target. Devices look to the OTA system for the latest Target they should run. Operators oversee the intersection of these goals.

The point of the Factory is to create Targets. The magic of the Factory is how a simple git push can make this all happen and is where you can start to visualize a Factory. The Factory Definition file instructs CI what it’s supposed to build when changes hit The default factory-config.yml tells CI:

  • If an LmP change (lmp-manifest.git or meta-subscriber-overrides.git) comes in on the master branch, do a platform build and tag it with “master”.
  • If a container change (containers.git) comes in on master branch, do a container build and tag it with master.

However, this can grow much more complex.

CI must also take into account that Targets require both an OSTree image and Compose Apps. This turns out to be a fairly simple calculation. CI looks at the previous Target for a given tag. In the case of a platform build, it will copy the Compose Apps defined for it. In the case of a container build, it will copy the OSTree hash. In this way, there aren’t “container targets” and “platform targets”. There are only Targets.

Visualizing a Factory

Start with factory-config.yml. The tagging and ref_options stanzas describe the intent. Then take a high-level view of the fleet:

$ fioctl status
Total number of devices: 2

---     -------  ----------  ------
master  2        1           1

## Tag: master
  ------  -------  -------
  46      1        `fioctl targets show 46`
  112     1        `fioctl targets show 112`

This will show all Targets active in the field. Now take a look at a specific Target:

$ fioctl targets show 46

## Target: intel-corei7-64-lmp-46-master
       Created:       2022-03-22T15:23:03Z
       Tags:          master
       OSTree Hash:   8f8a74e0fac31c1c3f43d737246e7320d453c377c6724c398a506b857d224e55


       APP          HASH
       ---          ----
       shellhttpd   sha256:e4a7b3a31c0126d28aaf75e1b8b6e83c7afd160b110267530b8572ce192160da

This command gives the exact details of the Target, including the CI change that produced it.