Bootstrapping

During the production and provisioning of devices, a standard image is usually flashed onto each device. This image is identical across all devices to maintain consistency and simplify the provisioning process. After flashing the image, each device is then typically booted for the first time as part of an end-of-line configuration and quality assurance testing procedure. This initial boot process can also be used for setting up and initializing device-specific configurations, a process to which we refer as bootstrapping.

The bootstrapping process can include a variety of steps such as:

• Growing the partition table to utilize the full storage capacity of the device.
• Creating necessary partitions and filesystems that are not part of the image.
• Initializing on-device chips and one-time-programmable storage.
• Generating unique device identifiers and security certificates.
• Customizing configurations to suit device-specific requirements.

When configured to run before the init system, Rugix Ctrl can also carry out bootstrapping steps. For instance, unless configured otherwise, it will grow the partition table and initialize the data partition where the persistent state lives. Rugix Ctrl’s bootstrapping process is flexible and you can adapt it to your specific needs by adding bootstrapping hooks. Note that the bootstrapping process runs very early during the boot process before the init system because properly booting the system, in particular, with state management, requires the existence of a data partition, which may first need to be created.

System Layout

While one may choose to already prepare the provisioning image and its partition table for the exact storage capacity of a device, this may not always be feasible. Maybe you have different variants of a device with different storage capacities and want to use the same image for all of them, or you may want your users to be able to flash an image onto their own storage media. In these cases, the partition table of the image will not match the storage capacity and typically does not even contain all the required partitions, such as redundant system partitions and the data partition. In that case, you can configure Rugix Ctrl to adapt the partition table and create the necessary partitions and filesystems. The desired system layout is defined in the layout configuration section.

Custom Layouts

Rugix Ctrl supports MBR (DOS) partition tables and GPT partition tables. Here are two example layouts:

[layout]
type = "mbr"
partitions = [
    { name = "config", size = "256MiB", type = "0c" },
    { name = "boot-a", size = "128MiB", type = "0c" },
    { name = "boot-b", size = "128MiB", type = "0c" },
    { name = "extended", type = "05" },
    { name = "system-a", size = "6GiB" },
    { name = "system-b", size = "6GiB" },
    { name = "data", filesystem = { type = "ext4" } },
]

[layout]
type = "gpt"
partitions = [
    { name = "EFI", size = "256MiB", type = "C12A7328-F81F-11D2-BA4B-00A0C93EC93B" },
    { name = "boot-a", size = "256MiB" },
    { name = "boot-b", size = "256MiB" },
    { name = "system-a", size = "6GiB" },
    { name = "system-b", size = "6GiB" },
    { name = "data", filesystem = { type = "ext4" } },
]

Both layouts prepare the system for an A/B update setup with two boot and two system partitions. The last partition is not required to have a size, in which case, it will take up the entire remaining space. So, in case of the examples, the data partition will take up all the remaining space. In case of an MBR partition table, the extended partition also does not require a size and will extend to the end of the disk. The filesystem option is optional and will cause Rugix Ctrl to create a filesystem. The type option is also optional defaulting to 83 and 0FC63DAF-8483-4772-8E79-3D69D8477DE4 for MBR and GPT, respectively.

Default Layout

For a typical system, you would use one of the layouts above. As a shortcut, the type of the layout can be set to default. In that case, only a system-size needs to be configured. Rugix Ctrl will then automatically create a matching partition table based on the type of table it finds on the root disk and the configured system size. Here is an example:

[layout]
type = "default"
system-size = "4GiB"

Disable Partition Creation

If you do not want Rugix Ctrl to create any partitions, simply set the layout’s type to none:

[layout]
type = "none"

Configuration Reference

For reference, here is the complete schema for the bootstrapping configuration file:

mbr

ext4

gpt

ext4

default

none

You will find the most recent version of this schema on GitHub.