The Mender client is a user space Linux executable with one main purpose: to install software updates to the device it is running on. Broadly speaking, there are two types of updates: full filesystem when you update the complete filesystem, and application updates where, for example, you change one file, install some packages, or execute arbitrary commands. Device integration is the set of steps needed to ensure Mender is running on your system, with appropriate configuration for your update type.
In most instances, the full filesystem update will use a redundant root filesystem partition and the application updates will update components in the active root filesystem.
If Mender is to be used only for application updates, then it can be installed like any other application using your system package management utilities. You can find more details about this in the section on Install with Debian package
To support full file system updates, a more thorough integration is required which includes install Mender on top of a running operating system as well as modifying the boot commands and providing extra partitions. The mechanisms used for this are specific to the distribution or build system you are using to maintain your image. We provide detailed instructions for full system integration with the Yocto Project and with Debian-based distributions.
For a more general overview of where the Mender client fits in as part of the deployment process, please see the Architecture overview.
At its basics, the definition of Device integration includes
To use robust system updates with Mender, your bootloader needs to be updated with logic to select the appropriate partition at boot time. Additionally, utilities that can update the bootloader environment need to be installed into the root filesystem.
The Mender client application is a standard Linux executable that is installed into the root filesystem. If your design uses managed mode, you also need to ensure that the Mender client is running as a system servce.
The Mender configuration files need to be installed into your root filesystem. These are standard text files containing JSON code that defines parameters for the Mender client, such as polling intervals.
If you require support of payload types other than the full root filesystem updates, you will need to ensure that appropriate Update Modules are installed into your root filesystem, to be invoked by the Mender client.
If you require support of root filesystem State Scripts, you need to ensure that they are installed into your root filesystem, to be invoked by the Mender client.
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