Containers and Jaguar

Jaguar is Toit's development tool. It dynamically installs and runs program (as containers) on devices.

Prerequisites

We assume that you have read the container introduction.

Listing containers

When Jaguar is flashed onto a device (with jag flash) it automatically adds a service version of Jaguar as container to the device. All other programs that are executed or installed with Jaguar are installed dynamically.

After flashing Jaguar onto a device, you can list the installed containers:

jag container list

By default this should list a single container called jaguar.

ᐅ jag container list
DEVICE     IMAGE                                  NAME
kind-bet   cfdacf51-230f-2628-53dc-fe8c011c0ae6   jaguar

Installing containers

You can install additional containers with the jag container install:

jag container install hello hello.toit

Note that Jaguar automatically compiles the given program (hello.toit) into a snapshot before installing it.

Containers that are installed this way are automatically started after installation and at boot time.

Uninstalling containers

You can uninstall containers with jag container uninstall:

jag container uninstall hello

Disabling Jaguar

Sometimes it can be useful or necessary to disable Jaguar when running a specific container.

This can be done by installing the container with the -D jag.disabled flag:

jag container install -D jag.disabled hello hello.toit

At the next boot this gives the container 10 seconds to run before Jaguar is started. If 10 seconds is not enough, you can specify a different timeout with -D jag.timeout=<duration>, where <duration> is a duration string like 10s or 1m.

Example:

jag container install -D jag.disabled -D jag.timeout=1m hello hello.toit

Use cases

The primary use case for disabling Jaguar is to run a container that needs full access to the WiFi module. For example, a container that implements a WiFi access point. The provision package falls into this category.

Disabling Jaguar can also be used to limit battery usage. For example, a program could sample a sensor at regular intervals and immediately go to deep-sleep without giving Jaguar a chance to run and start the WiFi. Only if a certain condition is met (like a button is pressed), it could avoid the call to deep-sleep and instead let Jaguar run.