Description An Update Module to install binary delta rootfs updates on a device. This Update module is available with a commercial Mender plan. Please refer to the Mender.io product page for more information about commercial plans, and sign up for a free trial for Mender Professional here. Example use-cases: Perform a rootfs update using far less bandwidth than a traditional full-image update Specification Specification Module name mender-binary-delta Supports rollback yes Requires reboot yes Artifact generation script yes Full operating system updater yes Source code Closed source Maintainer Northern.tech Prerequisites An existing Yocto environment with a Mender board integration working to be able to deploy “rootfs-image” updates Ability to use read only root filesystem in your build (how to enable it is shown below, Delta updates will not work without it) A Mender Professional or Mender Enterprise account. Sign up for a free trial for Mender Professional. The mender-artifact CLI tool. You can download it by following instructions from the respective section of Mender Docs. Mender client mender-binary-delta requires “read-only” rootfs If you do not already have “read-only” mode on your rootfs images you can enable this with adding the following in e.g local.conf IMAGE_FEATURES_append = " read-only-rootfs" It is a good idea to enable this first and test that your device is still operating as intended, before proceeding in testing mender-binary-delta. Get mender-binary-delta Change directory to $HOME: cd ${HOME} Now, follow the instructions from the respective section of the Mender Docs to download and unpack the mender-binary-delta tarball. You should get the following files in a mender-binary-delta-x.y.z directory (with x.y.z replaced by a real version): . ├── aarch64 │ ├── mender-binary-delta │ └── mender-binary-delta-generator ├── arm │ ├── mender-binary-delta │ └── mender-binary-delta-generator └── x86_64 ├── mender-binary-delta └── mender-binary-delta-generator As you might have guessed, we have prepared binaries for the aarch64, armhf and x86_64 architectures. If your platform architecture does not match the provided binaries, please contact us and we should be able to compile binaries for your target. The mender-binary-delta binary is intended to be installed on the device on which you intend to perform delta updates on. However, the Yocto integration works directly with the .tar.xz file, so we don’t need the binary here. The mender-binary-delta-generator is intended to be used on your development machine to generate deltas between two Mender Artifacts. We only need the generator, so copy it to /usr/bin[1]: sudo cp mender-binary-delta-?.?.?/$(uname -m)/mender-binary-delta-generator /usr/bin/ Then delete the rest of the unpacked files: rm -rf mender-binary-delta-?.?.? Integrating mender-binary-delta to an existing Yocto environment It is assumed that you already have a Yocto Project environment configured using meta-mender and that you are in the build directory. Add meta-mender-commercial layer to your Yocto environment: bitbake-layers add-layer ../sources/meta-mender/meta-mender-commercial Add the following to your local.conf (with x.y.z replaced with the actual version of mender-binary-delta obtained above) to include mender-binary-delta in your build: cat > conf/local.conf # Customizations for Mender delta-update support # This will not impact your image if you already have this enabled IMAGE_FEATURES:append = " read-only-rootfs" IMAGE_INSTALL:append = " mender-binary-delta" LICENSE_FLAGS_ACCEPTED:append = " commercial_mender-yocto-layer-license" SRC_URI:pn-mender-binary-delta = "file://${HOME}/mender-binary-delta-x.y.z.tar.xz" EOF Preparing images and artifacts For the purpose of this tutorial you can set the MENDER_ARTIFACT_NAME to the following: MENDER_ARTIFACT_NAME = "release-v.1.0" Set helper variables (update with the appropriate values used in your environment): TARGET_IMAGE="core-image-base" MACHINE="raspberrypi4" Build an image (target image might differ in your environment): bitbake ${TARGET_IMAGE} Use the output of the build to provision your device with e.g with the provided disk image (e.g .sdimg) file. The result should be that you have a device that has booted and has the following file installed: # ls /usr/share/mender/modules/v3/mender-binary-delta -alh -rwxr-xr-x 1 root root 98.2K Aug 19 08:52 /usr/share/mender/modules/v3/mender-binary-delta Please verify this before proceeding. Save the generated Mender Artifact for later (will be used to generate a delta): cp tmp/deploy/images/${MACHINE}/${TARGET_IMAGE}-${MACHINE}.mender ${HOME}/release-v.1.0.mender Generate a second Mender Artifact which can be used to test deploying delta updates. Start of with making a change to the image content, such as adding an ssh server (for diagnostics purposes): cat > conf/local.conf IMAGE_INSTALL_append = " openssh" EOF Update the MENDER_ARTIFACT_NAME to the following: MENDER_ARTIFACT_NAME = "release-v.2.0" Build the new image (target image might differ in your environment): bitbake ${TARGET_IMAGE} Save the generated Mender Artifact for later (will be used to generate a delta): cp tmp/deploy/images/${MACHINE}/${TARGET_IMAGE}-${MACHINE}.mender ${HOME}/release-v.2.0.mender Generating delta Artifacts This tutorial assumes that Mender Enterprise is being used. If not, then dependencies between Artifacts need to be tracked manually, which is not recommended. See the troubleshooting section for ways to deal with this. Generate delta for v1.0 -> v2.0 update path: mender-binary-delta-generator -o v2.0-deltafrom-v1.0.mender release-v.1.0.mender release-v.2.0.mender Generate delta for v2.0 -> v1.0 update path: mender-binary-delta-generator -o v1.0-deltafrom-v2.0.mender release-v.2.0.mender release-v.1.0.mender Using the delta Mender Artifacts We should have now have the Mender Artifacts ready and you can upload them to the Mender server. The uploaded files should be: release-v.1.0.mender (rootfs-image) release-v.2.0.mender (rootfs-image) v1.0-deltafrom-v2.0.mender (mender-binary-delta) v2.0-deltafrom-v1.0.mender (mender-binary-delta) After having uploaded these four Artifacts, you should have two Releases in the Mender UI. This is because the rootfs-image Artifact and the corresponding mender-binary-delta Artifact are referring to the same software. If you have followed this tutorial your provisioned device should be running release-v1.0 which was provisioned using a disk image (e.g sdimg). Deploy delta updates Start off with deploying release-v.2.0.mender to the device, and once that is completed you can deploy release-v.1.0.mender. Note that at this point there is no distinction between deploying a full rootfs-image Artifact and a mender-binary-delta Artifact. Mender keeps track of dependencies automatically and selects the correct one. More formally, it selects the smallest Artifact which satisfies the dependencies, but will select the bigger rootfs-image Artifact if the device has an unknown delta base. If you want to verify that the mender-binary-delta Artifact is indeed being used, delete the rootfs-image from the one of the Releases in the UI, and then deploy that release. Troubleshooting Error message: Artifact dependency "rootfs_image_checksum" not satisfied by currently installed artifact This message is usually because of one of these reasons: You are using mender-binary-delta version 1.1.1 or earlier together with Mender Server 2.6.0 or later, or together with mender-artifact 3.5.0 or later. For this to work correctly you need to upgrade mender-binary-delta to 1.2.0 or later. You are using a non-Enterprise version of Mender, and there are several mender-binary-delta and/or rootfs-image Artifacts with the same name (grouped under the same Release in the UI). In non-Enterprise versions of Mender, there is no automatic dependency tracking, so each Artifact needs to have a different name, even if the only difference between two Artifacts is the delta base. You are trying to deploy a mender-binary-delta Artifact onto a device which does not have the delta base checksum that the Artifact was made for. If this is the case, you need to make a new mender-binary-delta Artifact based on the Artifact which is currently installed on the device, and install that instead. It can also be an indication that the very first rootfs-image Artifact has not been deployed yet. If so, you need to install a rootfs-image Artifact to the device first, and make sure that the next mender-binary-delta Artifact uses this Artifact as a base. This only needs to be done once for each device. This requirement may be lifted in the future. Deployment finishes with “No artifact” without updating the device This usually happens for one of three reasons: The device has never received a rootfs-image Artifact update. The Release which is being deployed only has mender-binary-delta Artifacts uploaded, and none of them match the delta base on the device. The client is version 2.2 or older, and therefore it doesn’t know how to ask for a delta Artifact. These are the solutions for each case: Upload the corresponding rootfs-image Artifact, which will be used in the deployment instead of the mender-binary-delta Artifact. This only needs to be done once for each device. This requirement may be lifted in the future. Upload a mender-binary-delta Artifact using the currently installed Artifact of the device as a base. Alternatively, solution number 1 is a valid solution for case number 2 as well, but it will use more bandwidth. Solution number 3 is the same as for the error message type_info depends values not yet supported, described below. Error message: type_info depends values not yet supported This can happen if the client is too old to support the dependency tracking information present in mender-binary-delta 1.1 and later. If you encounter this you can specify the --make-transitional argument when making the delta Artifact using mender-binary-delta-generator. The resulting Artifact will not have any dependency information associated with it, and you must give it a different name from the original Artifact it was made from, using the -n argument. For example: ./mender-binary-delta-generator -o v2.0-deltafrom-v1.0.mender --make-transitional -n v2.0-deltafrom-v1.0 release-v.1.0.mender release-v.2.0.mender Note that if you use this, the original rootfs-image Artifact must have been created with the --no-checksum-provide argument (without this you would not have been able to install the original rootfs-image Artifact either). See the bullet point about --no-checksum-provide in the changelog for mender-artifact 3.3.0 for more information. Error messages when trying to use mender-binary-delta with UBIFS UBIFS support requires at least mender-binary-delta version 1.5.0. In addition, either mender-flash or ubiupdatevol need to be installed on the device, and the FlashTool configuration setting must be set to one of them. On Yocto, the you can use the MENDER_FLASH_TOOL variables to control this (defaults to mender-flash). Note that the development machine’s architecture determines which binary to use. This is independent on the architecture of the device where the resulting delta Mender Artifact will be deployed. ↩︎

Why this update module depend on Yocto?

@shainert.israel Hi This could be run on other systems also, however, Yocto is set as a dependency due to the read-only rootfs requirement. So this is where we test it.

Is this update’s generation and deployment based on full roofs partition binary file delta or is file based delta? I mean, when generating the update, does it take as input a base rootfs image file and a target rootfs image file and create a binary diff, or it mount them both and compare the file-system files (optionally with exclude list) and put in the update any file that is different?

Hi @oleorhagen, I didn’t understand your answer, please see a clarification of my question (edited). Thank You

Hi @shainert.israel, I’m sry, my response was a bit short. It does the former. Meaning that it creates a binary diff from two rootfs images. No mounting is done. In fact, currently we are using the xdelta binary diff algorithm

Is this also available with debian images for raspberry pi?

Not out of the box I am afraid. The reason is that the deltas need a read only filesystem to work on, and this is not the case for the raspbian debian images. I guess it should be possible though, but I have not looked into it myself. Another way of doing this could be to maybe write an rsync update module, or something similar, which does the diffing on the fly :slight_smile:

Is this something that will be supported out of the box in a Debian image eventually? This lack of support causes us to not use Mender in our product.

It depends mostly on Raspbian/Debian. The problem is that Debian isn’t typically installed in a read-only mode. You can take a look at this document to see how to use a read-only image with Debian. If you can get that working, then Binary Delta updates should work as well. But my gut feeling is that it’s easier to use Yocto for this, and probably there will be less surprises as well.

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Robust delta update rootfs

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