Image replicator intro

This platform supports our Image Replicator tool. The Image Replicator tool is intended for use by developers as a means to write bootable images or filesystems onto a device's media (SD / eMMC / SATA / etc.) as part of the developer's production or preparation process. In addition to writing media, the Image Replicator tool can capture images from a device's media and prepare them to be written to other devices.

The Image Replicator tool is a USB disk image that boots from a target device to capture or write USB drive-resident media directly onto the target without a host workstation. It runs from a USB drive and allows:

• Capturing an image of the device storage (eMMC/microSD)
• Writing an existing image back to media
• Creating bootable media for mass deployment

The USB disk image is based on Buildroot and contains a set of scripts that handle the capture and write processes. The processes and scripts are flexible, can be used as-is, or adapted into larger production processes to format and load data onto devices. A single USB drive can be used to capture images from a device and then, once inserted in to other devices, write those same images onto other devices. The capture process is not necessary if it is not needed. Images for the target device can be copied to the USB drive, booted on compatible units, and have the target images written to that unit's media.

Image Capture Process

The image capture process performs the following steps. For more detailed information, see the Image Capture section below.

1. If no valid images exist on the disk, image capture starts.
2. For each valid media present on the unit, a bit for bit copy of the source is made.
3. This image is mounted, sanitized (to remove unneeded files and allow safe copying of the image to other units), and saved as either a disk image or a tarball, depending on the partition layout of the source disk.
4. All images and tarballs are compressed, with both the output files' MD5 hash saved, as well as all of the files contained in the root partition (MD5 hashes saved) to a file for later verification.

The captured images and tarballs are named such that the USB Image Replicator disk can be immediately used to boot another unit and have it perform the Image Write process, writing that unit's media with the captured images.

Note:

When using this process, the USB drive used for the Image Replicator must be sized large enough to handle multiple compressed images as well as the uncompressed copy of an active media image. If the image capture process runs out of space, the process indicates a failure.

Image Write Process

The image write process performs the following steps. For more detailed information see the Image Write section below.

1. For each valid media present on the unit, find the first valid source image file for it.
2. If a source image exists for a media that is not present on the unit, then the process indicates a failure.
3. If the source image is a tarball, format the target disk with an appropriate file system and unpack it to the target disk, verifying all files against the MD5 hash file list after they are written.
4. If the source image is a disk image, write that to the target disk. If an MD5 file for the disk image exists, read back the written disk and compare it to the hash.