3. Using RAUC

For using RAUC in your embedded project, you will need to build at least two versions of it:

  • One for your host (build or development) system. This will allow you to create, inspect and modify bundles.

  • One for your target system. This can act both as the service for handling the installation on your system, or as a command line tool that allows triggering the installation, inspecting your system and obtaining bundle information.

All common embedded Linux build system recipes for RAUC will solve the task of creating appropriate binaries for you as well as caring for bundle creation and partly system configuration. If you intend to use RAUC with Yocto, use the meta-rauc layer, in case you use PTXdist, simply enable RAUC in your configuration.


When using the RAUC service from your application, the D-Bus interface is preferable to using the provided command-line tool.

3.1. Creating Bundles

To create an update bundle on your build host, RAUC provides the bundle sub-command:

rauc bundle --cert=<certfile|certurl> --key=<keyfile|keyurl> <input-dir> <bundle-name>

The <input-dir> must point to a directory containing all images, scripts and other files that should be part of the created update bundle. Additionally, a RAUC manifest file manifest.raucm is expected in <input-dir>. The manifest describes the bundle content and the purpose of each included image.

The created bundle will be stored under the given <bundle-name>.

The --cert and --key argument specify the certificate and private key for signing the bundle. They can be provided either as PEM files or as PKCS#11-URIs (to avoid storing sensitive key material as plain files).

With the optional --signing-keyring=<certfile> argument, the signed bundle can be verified against the keyring file as part of the bundle creation process, for example to prevent signing with invalid or expired certificates.


A more detailed description of how to create bundles can be found in the Bundle Generation section in the Integration chapter.

3.2. Obtaining Bundle Information

rauc info --keyring=<certfile> [--output-format=<format>] <input-file>

The info command lists the basic meta data of a bundle (compatible, version, build-id, description) and the images and hooks contained in the bundle.

To authenticate the bundle information, it needs to be verified against a keyring. You can provide it via the system configuration or the --keyring argument. If the verification should explicitly be skipped, you may also use --no-verify instead.

You can control the output <format> depending on your needs. By default (or with readable), it will print a human readable representation of the bundle not intended for being processed programmatically. Alternatively, with shell you can obtain a shell-parsable description or a JSON representation of the bundle content with json-2.

3.3. Installing Bundles

To actually install an update bundle on your target hardware, RAUC provides the install command:

rauc install <bundle>

The <bundle> argument can be a local path, a local file URI, or a remote (HTTP/HTTPS) URL.

Alternatively you can trigger a bundle installation using the D-Bus API.


Installing a bundle requires RAUC to be integrated in your system. Refer to the Integration chapter for more.

3.4. Accessing the System Status

For debugging purposes and for scripting it is helpful to gain an overview of the current system as RAUC sees it. The status command allows this:

rauc status [--detailed] [--output-format=<format>]

You can choose the output <format> depending on your needs. By default (or with readable), it will print a human readable representation of your system’s most important properties. Alternatively, with shell you can obtain a shell-parsable description, or with json or json-pretty a JSON representation of the system status. If more information is needed such as the slots’ status add the command line option --detailed.

3.5. React to a Successfully Booted System/Failed Boot

Normally, the full system update chain is not complete before being sure that the newly installed system runs without any errors. As the definition and detection of a successful operation is really system-dependent, RAUC provides commands to preserve a slot as being the preferred one to boot or to discard a slot from being bootable.

rauc status mark-good

After verifying that the currently booted system is fully operational, one wants to signal this information to the underlying bootloader implementation which then, for example, resets a boot attempt counter.

rauc status mark-bad

If the current boot failed in some kind, this command can be used to communicate that to the underlying bootloader implementation. In most cases this will disable the currently booted slot or at least switch to a different one.

Although not very useful in the field, both commands recognize an optional argument to explicitly identify the slot to act on:

rauc status mark-{good,bad} [booted | other | <SLOT_NAME>]

This is to maintain consistency with respect to rauc status mark-active where that argument is definitively wanted, see here.

3.6. Manually Switch to a Different Slot

One can think of a variety of reasons to switch the preferred slot for the next boot by hand, for example:

  • Recurrently test the installation of a bundle in development starting from a known state.

  • Activate a slot that has been installed sometime before and whose activation has explicitly been prevented at that time using the system configuration file’s parameter activate-installed.

  • Switch back to the previous slot because one really knows better™.

To do so, RAUC offers the subcommand

rauc status mark-active [booted | other | <SLOT_NAME>]

where the optional argument decides which slot to (re-)activate at the expense of the remaining slots. Choosing other switches to the next bootable slot that is not the one that is currently booted. In a two-slot-setup this is just… the other one. If one wants to explicitly address a known slot, one can do so by using its slot name which has the form <slot-class>.<idx> (e.g. rootfs.1), see this part of section System Configuration File. Last but not least, after switching to a different slot by mistake, before having rebooted this can be remedied by choosing booted as the argument which is, by the way, the default if the optional argument has been omitted. The date and time of activation as well as the number of activations is part of the slot’s metadata which is stored in the slot status file, see section Slot Status.

3.7. Customizing the Update

RAUC provides several ways to customize the update process. Some allow adding and extending details more fine-grainedly, some allow replacing major parts of the default behavior of RAUC.

In general, there exist three major types of customization:

  • configuration parameters (in rootfs config file /etc/rauc/system.conf)

  • handlers (executables in rootfs)

  • hooks (executables in bundle)

The first type, configuration parameters, allow controlling parameters of the update in a predefined way.

The second type, using handlers, allows extending or replacing the installation process. They are executables (most likely shell scripts) located in the root filesystem and configured in the system’s configuration file. They control static behavior of the system that should remain the same over future updates.

The last type are hooks. They are similar to handlers, except that they are contained in the update bundle. Thus they allow to flexibly extend or customize one or more updates by some special behavior. A common example would be using a per-slot post-install hook that handles configuration migration for a new software version. Hooks are especially useful to handle details of installing an update which were not considered in the previously deployed version.

In the following, configuration parameters, handlers and hooks will be explained in more detail.

3.7.1. System Configuration Parameters

Beside providing the basic slot layout, RAUC’s system configuration file (system.conf) also allows you to configure parts of its runtime behavior, such as handlers (see below), paths, etc. For a detailed list of possible configuration options, see System Configuration File section in the Reference chapter.

3.7.2. System-Based Customization: Handlers

Handlers are executables located in the target’s root file system that allow extending the installation process on system side. They must be specified in the targets System Configuration File.

For a detailed list of all environment variables exported for the handler scripts, see the Custom Handlers (Interface) section.

Pre-Install Handler


RAUC will call the pre-install handler (if given) during the bundle installation process, right before calling the default or custom installation process. At this stage, the bundle is mounted, its content is accessible and the target group has been determined successfully.

If calling the handler fails or the handler returns a non-zero exit code, RAUC will abort installation with an error.

Post-Install Handler


The post-install handler will be called right after RAUC successfully performed a system update. If any error occurred during installation, the post-install handler will not be called.

Note that a failed call of the post-install handler or a non-zero exit code will cause a notification about the error but will not change the result of the performed update anymore.

A possible usage for the post-install handler could be to trigger an automatic restart of the system.

System-Info Handler


The system-info handler is called after loading the configuration file. This way it can collect additional variables from the system, like the system’s serial number.

The handler script can return variables by echoing <VARIABLE-NAME>=<value> to stdout, like RAUC_SYSTEM_SERIAL or RAUC_SYSTEM_VARIANT.

3.7.3. Bundle-Based Customization: Hooks

Unlike handlers, hooks are defined in the update bundle and must be specified in the bundle’s Manifest file. All hooks are handled by a common executable that must be included in the bundle. Hooks allow the author of a bundle to add or replace functionality for the installation of a specific bundle. This can be useful for performing additional migration steps, checking for specific previously installed bundle versions or for manually handling updates of images RAUC cannot handle natively.

To reduce the complexity and number of files in a bundle, all hooks must be handled by a single executable that is registered in the bundle’s manifest:


The filename must match the name of the script or binary executable placed inside the content folder the bundle is generated from.

The actual hook invocations must be registered in the respective [image.*] or [hooks] manifest sections via hooks=<hook-names> settings where <hook-names> is a ;-separated list of hooks to invoke.

For each invoked hook, the common hook executable will be called with a specific argument indicating the name of the invoked hook. The executable is responsible for multiplexing the different hook calls.

In the following the available hooks are listed. Depending on their purpose, some are image-specific, i.e. they will be executed for the installation of a specific image only, while some other are global. Install Hooks

Install hooks operate globally on the bundle installation.

For a detailed list of all environment variables exported for the hooks executable, see the Install Hooks Interface section.

For install hooks, the hook call argument is just the hook name itself (e.g. install-check).

Install-Check Hook


This hook will be executed instead of the normal compatible check in order to allow performing a custom compatibility check based on compatible and/or version information.

To indicate that a bundle should be rejected, the script must return with an exit code >= 10.

If available, RAUC will use the last line printed to standard error by the hook executable as the rejection reason message and provide it to the user:


case "$1" in
                if [[ "$RAUC_MF_COMPATIBLE" != "$RAUC_SYSTEM_COMPATIBLE" ]]; then
                        echo "Compatible does not match!" 1>&2
                        exit 10
                exit 1

exit 0 Slot Hooks

Slot hooks are called for each slot an image will be installed to. In order to enable them, you have to specify them in the hooks key under the respective image section.

Note that hook slot operations will be passed to the executable with the prefix slot-. Thus if you intend to check for the pre-install hook, you have to check for the argument to be slot-pre-install.

For a detailed list of all environment variables exported for the hooks executable, see the Slot Hooks Interface section.

Pre-Install Hook

The pre-install hook will be called right before the update procedure for the respective slot will be started. For target slot types that represent a mountable file system, the hook will be executed with the target slots’ file system mounted. Note that a broken or unformatted target slot will currently cause the installation to be aborted with an error.



Post-Install Hook

The post-install hook will be called right after the update procedure for the respective slot was finished successfully. For slot types that represent a mountable file system, the hook will be executed with having the file system mounted. This allows to write some post-install information to the slot. It is also useful to copy files from the currently active system to the newly installed slot, for example to preserve application configuration data.



An example on how to use a post-install hook:


case "$1" in
                # only rootfs needs to be handled
                test "$RAUC_SLOT_CLASS" = "rootfs" || exit 0

                touch "$RAUC_SLOT_MOUNT_POINT/extra-file"
                exit 1

exit 0

Install Hook

The install hook will replace the entire default installation process for the target slot of the image it was specified for. Note that when having the install hook enabled, pre- and post-install hooks will not be executed and having an image (i.e. filename set) is optional, too! The install hook allows to fully customize the way a slot is updated. This allows performing special installation methods that are not natively supported by RAUC, for example to upgrade the bootloader to a new version while also migrating configuration settings.



or, without filename:



3.7.4. Full Custom Update

For some special tasks (recovery, testing, migration), it might be required to completely replace the default RAUC update mechanism and to only use its infrastructure and the signature verification for executing an application or a script on the target side.

For this case, RAUC allows to define a full custom handler in a bundle’s manifest that will be executed instead of the built-in slot update handling:

compatible=Test Platform


The handler script/binary must be part of the bundle.

Refer manifest [handler] section description for details about how the full custom handler can be configured and gets called.

3.8. Using the D-Bus API

The RAUC D-BUS API allows seamless integration into existing or project-specific applications, incorporation with bridge services such as the rauc-hawkbit client and also the rauc CLI uses it.

The API’s service domain is de.pengutronix.rauc while the object path is /.

3.8.1. Installing a Bundle

The D-Bus API’s main purpose is to trigger and monitor the installation process via its Installer interface.

The InstallBundle method call triggers the installation of a given bundle in the background and returns immediately. Upon completion of the installation RAUC emits the Completed signal, indicating either successful or failed installation. For details on triggering the installation process, see the The InstallBundle() Method chapter in the reference documentation.

While the installation is in progress, constant progress information will be emitted in form of changes to the Progress property.

3.8.2. Processing Progress Data

The progress property will be updated upon each change of the progress value. For details see the The “Progress” Property chapter in the reference documentation.

To monitor Progress property changes from your application, attach to the PropertiesChanged signal and filter on the Operation properties.

Each progress step emitted is a tuple (percentage, message, nesting depth) describing a tree of progress steps:

├"Installing" (0%)
│ ├"Determining slot states" (0%)
│ ├"Determining slot states done." (20%)
│ ├"Checking bundle" (20%)
│ │ ├"Verifying signature" (20%)
│ │ └"Verifying signature done." (40%)
│ ├"Checking bundle done." (40%)
│ ...
└"Installing done." (100%)

This hierarchical structure allows applications to decide for the appropriate granularity to display information. Progress messages with a nesting depth of 1 are only Installing and Installing done.. A nesting depth of 2 means more fine-grained information while larger depths are even more detailed.

Additionally, the nesting depth information allows the application to print tree-like views as shown above. The percentage value always goes from 0 to 100 while the message is always a human-readable English string. For internationalization you may use a gettext-based approach.

3.8.3. Examples Using busctl Command

Triggering an installation:

busctl call de.pengutronix.rauc / de.pengutronix.rauc.Installer InstallBundle sa{sv} "<bundle-path>/<bundle-url>" 0

Mark a slot as good:

busctl call de.pengutronix.rauc / de.pengutronix.rauc.Installer Mark ss "good" "rootfs.0"

Mark a slot as active:

busctl call de.pengutronix.rauc / de.pengutronix.rauc.Installer Mark ss "active" "rootfs.0"

Get the Operation property containing the current operation:

busctl get-property de.pengutronix.rauc / de.pengutronix.rauc.Installer Operation

Get the Progress property containing the progress information:

busctl get-property de.pengutronix.rauc / de.pengutronix.rauc.Installer Progress

Get the LastError property, which contains the last error that occurred during an installation.

busctl get-property de.pengutronix.rauc / de.pengutronix.rauc.Installer LastError

Get the status of all slots

busctl call de.pengutronix.rauc / de.pengutronix.rauc.Installer GetSlotStatus

Get the current primary slot

busctl call de.pengutronix.rauc / de.pengutronix.rauc.Installer GetPrimary

Monitor the D-Bus interface

busctl monitor de.pengutronix.rauc

Obtain bundle information

busctl call de.pengutronix.rauc / de.pengutronix.rauc.Installer InspectBundle sa{sv} "<bundle-path>/<bundle-url>" 0

3.9. Debugging RAUC

When RAUC fails to start on your target during integration or later during installation of new bundles it can have a variety of causes.

This section will lead you through the most common options you have for debugging what actually went wrong.

In each case it is quite essential to know that RAUC, if not compiled with -Dservice=false runs as a service on your target that is either controlled by your custom application or by the RAUC command line interface.

The frontend will always only show the ‘high level’ error output, e.g. when an installation failed:

rauc-Message: 08:27:12.083: installing /home/enrico/Code/rauc/good-bundle-hook.raucb: LastError: Failed mounting bundle: failed to run mount: Child process exited with code 1
rauc-Message: 08:27:12.083: installing /home/enrico/Code/rauc/good-bundle-hook.raucb: idle
Installing `/home/enrico/Code/rauc/good-bundle-hook.raucb` failed

In simple cases this might be sufficient for identifying the actual problem, in more complicated cases this may give a rough hint. For a more detailed look on what went wrong you need to inspect the rauc service log instead.

If you run RAUC using systemd, the log can be obtained using

journalctl -u rauc

When using SysVInit, your service script needs to configure logging itself. A common way is to dump the log e.g. /var/log/rauc.

It may also be worth starting the RAUC service via command line on a second shell to have a live view of what is going on when you invoke e.g. rauc install on the first shell.

3.9.1. Inspecting Bundle Contents

Sometimes during development, it is useful to check whether the bundle contents are as expected. While RAUC bundles could just be mounted as a squashfs, using rauc mount also uses the same checks and mechanisms as rauc install (device-mapper/loopback & network support). The bundle is mounted below the configured mount prefix (/mnt/rauc/bundle by default). When you are done, just use umount <mount point> to unmount the bundle.

$ rauc mount /var/tmp/test/good-verity-bundle.raucb
rauc-Message: 12:37:36.869: Reading bundle: /var/tmp/test/good-verity-bundle.raucb
rauc-Message: 12:37:36.889: Verifying bundle signature...
rauc-Message: 12:37:36.894: Verified inline signature by 'O = Test Org, CN = Test Org Release-1'
rauc-Message: 12:37:36.896: Mounting bundle '/var/tmp/test/good-verity-bundle.raucb' to '/mnt/rauc/bundle'
rauc-Message: 12:37:36.931: Configured loop device '/dev/loop0' for 24576 bytes
rauc-Message: 12:37:36.934: Configured dm-verity device '/dev/dm-0'
Mounted bundle at /mnt/rauc/bundle. Use 'umount /mnt/rauc/bundle' to unmount.
$ ls -l /mnt/rauc/bundle
total 21
-rw-r--r-- 1 root root 8192 Jun 21 14:51 appfs.img
-rwxr-xr-x 1 root root 2241 Sep 15  2017 custom_handler.sh
-rwxr-xr-x 1 root root 1421 Aug 31  2017 hook.sh
-rw-r--r-- 1 root root  308 Jun 21 14:51 manifest.raucm
-rw-r--r-- 1 root root 8192 Jun 21 14:51 rootfs.img
$ umount /mnt/rauc/bundle


This command is only intended for use during development.

3.9.2. Increasing Debug Verbosity

Both for the service and the command line interface it is often useful to increase the log level for narrowing down the actual error cause or gaining more information about the circumstances when the error occurs.

RAUC uses glib and the glib logging framework with the basic log domain ‘rauc’.

For simple cases, you can activate logging by passing the -d or --debug option to either the CLI:

rauc install -d bundle.raucb ..

or the service (you might need to modify your systemd or SysVInit service file).

rauc service -d

For more fine grained and advanced debugging options, use the G_MESSAGES_DEBUG environment variable. This allows enabling different log domains. Currently available are:


enable all log domains


enable default RAUC log domain (same as calling with -d)


enable logging of signature details

This will dump the full CMS structure during verification and can help identify problems with the signature details.


enable logging of subprocess calls

This will dump the entire program call invoked by RAUC and can help tracing down or reproducing issues caused by other programs invoked.

Example invocation:

G_MESSAGES_DEBUG="rauc rauc-subprocess" rauc service Enabling Verbose CURL Output

If you suspect an issue is related to network access (using the CURL library), you can set RAUC_CURL_VERBOSE=1. This will cause RAUC to enable CURLOPT_VERBOSE when configuring a CURL context.

3.9.3. Reproducing Issues using QEMU Test Setup

The RAUC source code repository provides a :ref:qemu-test sec-contributing-qemu-test script, mainly meant to be used for running the unit tests in a safe environment. But this can also be used to reproduce and debug basic functionality of rauc.

When running:

$ ./qemu-test system

you will boot into a QEMU shell that has a mocked RAUC setup allowing you to inspect status, install procedure, etc. For example:

root@qemu-test:/home/user/git/rauc# rauc status
=== System Info ===
Compatible:  Test Config
Booted from: rootfs.0 (A)

=== Bootloader ===
Activated: rootfs.0 (A)

=== Slot States ===
x [rootfs.0] (/dev/root, raw, booted)
        bootname: A
        mounted: /
        boot status: good
    [appfs.0] (/dev/null, raw, active)

o [rootfs.1] (/tmp/rootdev, raw, inactive)
        bootname: B
        boot status: good
    [appfs.1] (/tmp/appdev, raw, inactive)