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Introduction

You can use external storage (μSD card / USB device) for data exchange purpose (removable media). Can be used from Device Admin 1.16.

If a storage extension is required, please see documentation of Storage extension.

Attention

  • The data on the external storage (μSD card / USB device) is not encrypted. Others can unplug the device and can read the data on another devices.
  • The storage with ext4 and fat32 format are supported (formatting can be done in ctrlX UI: Settings->Storage).
  • There is no exclusive access to the medium for a singe application. Your data can be overwritten by other applications.
  • The data written to the storage cannot be encrypted.

Requirements

A storage is inserted, formatted and mounted:

If the storage is not formatted as fat32 or ext4, please format it first.

To format or mount a storage, use the according buttons in the details window of the Storage. The details window appears, when you select the according tile of the storage:

After the storage is mounted, the path is displayed on the details page of the storage:

Alternatively, the mount point is determinable in the ctrlX Data Layer (in Settings menu) under system/resources/storage

Configuration steps

To access the storage from your app (e.g. storage-test), use the removable-media interface as plug in the snapcraft.yaml of your application:

Example

snapcraft.yaml
name: storage-test # you probably want to 'snapcraft register name'
base: core20 # the base snap is the execution environment for this snap
version: '0.1' # just for humans, typically 'i.2+git' or '1.3.2'
summary: Single-line elevator pitch for your amazing snap # 79 char long summary
description: |
    <!--
    author: Company Name
    url: Company URL
    -->
    Short description of the app.

grade: devel # must be 'stable' to release into candidate/stable channeis
confinement: strict # use 'strict' once you have the right plugs and slots
architectures:
    - all
parts:
    storage:
        plugin: dump
        source: storage
apps:
    storage:
        command: bin/storage
        daemon: simple
        plugs:
            - removable-media

Usage

  • Install your app in ctrlX UI via Settings → Apps → Install from file.

  • After installation, you have permissions to read and write data in the mounted directory. The path is displayed in Storage details page /media/<storage>.