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Variables

This section provides a reference of variables Mender use during the Yocto Project build process. The variables are either specific to- and defined by Mender, as shown by the MENDER_ prefix, or defined by the Yocto Project and used by Mender.

ARTIFACTIMG_FSTYPE

Defines which file system type Mender will build for the rootfs partitions in the .biosimg, .sdimg, .uefiimg and the .mender file. See File system types for more information.

IMAGE_ROOTFS_SIZE

The size of the generated rootfs, expressed in kiB. This will be the size that is shipped in a .mender update. This variable is a standard Yocto Project variable and is influenced by several other factors. See the Yocto Project documentation for more information.

Note that this variable has no effect when generating a complete disk image (any suffix ending in img), since in that case the size is determined automatically. See MENDER_STORAGE_TOTAL_SIZE_MB for more information.

MENDER_ARTIFACT_EXTRA_ARGS

Flags added to this variable will be used as extra arguments to the mender-artifact tool when creating the .mender artifact. For example:

MENDER_ARTIFACT_EXTRA_ARGS_append = " -v 1"

The above example builds an artifact with the version 1 format.

MENDER_ARTIFACT_NAME

The name of the image or update that will be built. This is what the device will report that it is running, and different updates must have different names. This variable must be defined or the build will fail.

MENDER_ARTIFACT_SIGNING_KEY

Can be set to a private key which will be used to sign the update artifact. The default is empty, which means the artifact won't be signed.

The signature can also be added or changed outside the build process, by using the mender-artifact tool's -k option. For more information, see signing Mender Artifacts.

MENDER_ARTIFACT_VERIFY_KEY

If set, this will add the given public verification key to the client configuration, which means that the client will reject updates which are not signed by the corresponding private key (see MENDER_ARTIFACT_SIGNING_KEY).

More specifically, it will add the key to the root filesystem under /etc/mender/artifact-verify-key.pem, and add a ArtifactVerifyKey entry to mender.conf, pointing to this key. Using MENDER_ARTIFACT_VERIFY_KEY is recommended when the key is hosted in a file external to the build system / Yocto Project layer.

An alternative way to specify a verification key is to include a file named artifact-verify-key.pem in SRC_URI. This is a better approach if the key is hosted inside a Yocto Project layer, as opposed to living externally on the local host somewhere. Otherwise it has the same effect as defining MENDER_ARTIFACT_VERIFY_KEY.

Note that you cannot both use MENDER_ARTIFACT_VERIFY_KEY and have artifact-verify-key.pem in SRC_URI at the same time.

MENDER_BOOT_PART

The partition Mender uses as the boot partition. See More detailed storage configuration for more information.

MENDER_BOOT_PART_FSTYPE

Filesystem type of boot partition. This configuration is only used in fstab. Most filesystems can be auto detected, but some can not and hence this variable exists to override the auto detection.

MENDER_BOOT_PART_SIZE_MB

The size of the boot partition in the generated .biosimg, .sdimg or .uefiimg file. See Configuring the partition sizes for more information.

MENDER_DATA_PART

The partition Mender uses as the persistent data partition. See More detailed storage configuration for more information.

MENDER_DATA_PART_DIR

This variable and the associated method is obsolete in Yocto Project 2.5 sumo and later. Simply using recipes to put files in the /data partition is enough.

This variable is used to add files to the data partition of the Mender partitioned image. You will need to update your recipe file and your image file. The update to the recipe file ensures that the persistent files are deployed to a common location and the updates to the image file ensures that these files are included in the target image.

The changes needed in a particular recipe include inheriting the deploy class and ensuring that the persistent files are copied into the DEPLOYDIR for access by the image generation package.

inherit deploy
do_deploy() {
    install -d ${DEPLOYDIR}/persist
    install -m 0644 persistent.txt ${DEPLOYDIR}/persist
}
addtask do_deploy after do_compile before do_build

The changes to the image recipe will add the contents of persist directory to the .sdimg or .uefiimg file by setting the MENDER_DATA_PART_DIR variable.

MENDER_DATA_PART_DIR = "${DEPLOY_DIR_IMAGE}/persist"

The current implementation has a limitation of only one occurrence of MENDER_DATA_PART_DIR containing one directory.

MENDER_DATA_PART_FSTYPE

Filesystem type of data partition. This configuration is only used in fstab. Most filesystems can be auto detected, but some can not and hence this variable exists to override the auto detection.

MENDER_DATA_PART_SIZE_MB

The size of the persistent data partition in the generated .biosimg, .sdimg or .uefiimg file. See Configuring the partition sizes for more information.

MENDER_DEMO_HOST_IP_ADDRESS

As the name indicates, this variable is only relevant if you are building Mender with the meta-mender-demo layer. If set to an IP address, this variable sets the hostname resolution of the API gateway and the storage proxy (docker.mender.io and s3.docker.mender.io) to that address. The default is empty, which reverts to querying DNS (but note that the Docker setup comes with its own DNS server).

MENDER_DEVICE_TYPE

A string that defines the type of device this image will be installed on. This variable is only relevant when building a complete partitioned image (any suffix ending in img). Once a device is flashed with this, it will not change, even if the device is updated.

It defaults to the value of ${MACHINE}.

MENDER_DEVICE_TYPES_COMPATIBLE

A space separated string of device types that determine which types of devices this update is suitable for. This complements the MENDER_DEVICE_TYPE variable, and is only relevant when building a .mender update, not when building a partitioned image (any suffix ending in img).

It defaults to the value of ${MACHINE}.

MENDER_FEATURES_DISABLE

Features appended to this variable will be disabled in the build. See the section on features for more information.

MENDER_FEATURES_ENABLE

Features appended to this variable will be enabled in the build. See the section on features for more information.

MENDER_GRUB_STORAGE_DEVICE

The storage device, as referred to by GRUB (e.g. hd1). This variable can be used in cases where the Linux kernel and GRUB refer to the same device with different names. See The bootloader and the Linux kernel do not agree about the indexes of storage devices for more information.

MENDER_IMAGE_BOOTLOADER_BOOTSECTOR_OFFSET

Together with MENDER_IMAGE_BOOTLOADER_FILE, this sets the offset where the bootloader should be placed, counting from the start of the storage medium. The offset is specified in units of 512-byte sectors. Obviously this needs to be non-zero, or the partition table itself would be overwritten.

MENDER_IMAGE_BOOTLOADER_FILE

Together with MENDER_IMAGE_BOOTLOADER_BOOTSECTOR_OFFSET, this specifies a file that you would like to write directly into the boot sector, in the intervening space between the partition table and the first partition.

MENDER_IS_ON_MTDID

This variable is only relevant if the the mender-ubi feature is enabled. The variable should be set to the MTDID of the device that mender, and the root filesystem in particular, resides on. This is set automatically in cases where it's possible, but in some cases it must be set manually.

For example:

MENDER_MTDIDS = "nand0=20000000.flash"
MENDER_IS_ON_MTDID = "20000000.flash"

See also MENDER_MTDIDS.

MENDER_KERNEL_IMAGETYPE_FORCE

In certain build scenarios, the detection of kernel image type may not work for specific boards. This is usually caused by custom post-processing steps required to generate the images bypassing the standard Yocto logic. Setting this variable will ensure that Mender packages the proper files in these cases.

MENDER_MBR_BOOTLOADER_FILE

Specifies a first stage bootloader to flash to the very first sector of the storage device (Master Boot Record, or "MBR"), in the same sector as the partition table. This is often used on BIOS based systems and frequently in combination with MENDER_IMAGE_BOOTLOADER_FILE to flash a second stage bootloader on a later sector on the same storage device. The bootloader is normally very short, usually shorter than the sector size itself, so that the partition table will also fit on the same sector. The size of the bootloader is specified with MENDER_MBR_BOOTLOADER_LENGTH.

The default depends on which features are enabled. If mender-bios and mender-grub are enabled, then the default is the GRUB first stage bootloader, otherwise the default is empty.

MENDER_MBR_BOOTLOADER_LENGTH

The number of bytes to flash into the Master Boot Record (MBR) using MENDER_MBR_BOOTLOADER_FILE.

MENDER_MTD_UBI_DEVICE_NAME

The MTD part name where UBI volumes are stored.

Defaults to ubi when mender-ubi feature is on and building a .ubimg, otherwise the default is empty.

MENDER_MTDIDS

This variable is only relevant if the the mender-ubi feature is enabled, in which case it is mandatory. It lists the MTDID assignments on the system, separated by comma. For example:

MENDER_MTDIDS = "nand0=20000000.flash,nand1=30000000.flash"

If it has more than one entry, then MENDER_IS_ON_MTDID must be set too.

MENDER_MTDPARTS

This variable is only relevant if the the mender-ubi feature is enabled. The variable holds the MTDPARTS string for the Flash based device. This is set automatically in cases where it's possible, but in some cases it must be set manually. For example:

MENDER_MTDPARTS = "20000000.flash:1m(u-boot),-(ubi)"

Two volume names have special meaning to the Mender mtdimg image builder:

  • u-boot - The image builder will place the bootloader specified in MENDER_IMAGE_BOOTLOADER_FILE into this volume, if it is specified. Can be omitted if the platform doesn't need it.
  • ubi - The ubimg image (UBI image) will be put into this volume. The ubi volume should virtually always be present.

See also MENDER_MTDIDS.

MENDER_NAND_FLASH_PAGE_SIZE

This variable sets the page size, in bytes, of the NAND flash on the device, and is used to calculate parameters for the UBI volumes.

MENDER_PARTITIONING_OVERHEAD_MB

A rough estimate of space lost due to partition alignment, expressed in MB. The build process will calculate that automatically using a simple heuristic. See the definition of MENDER_PARTITIONING_OVERHEAD_MB in meta-mender for details on the calculation.

MENDER_PARTITION_ALIGNMENT

Alignment of partitions used when building partitioned images, expressed in bytes. Note that this is not always a whole number of KiB, particularly when the storage device is a UBI volume.

MENDER_ROOTFS_PART_A

The partition Mender uses as the first (A) rootfs partition. See More detailed storage configuration for more information.

MENDER_ROOTFS_PART_A_NAME

Alternative name for MENDER_ROOTFS_PART_A. Used if you need two different references to MENDER_ROOTFS_PART_A.

Example:

# will only accept a UBI volume name (but we normally work with index numbers e.g. `mender_boot_part`)
ubifsmount ubi0:rootfsa

Defaults to the value of ${MENDER_ROOTFS_PART_A} when building .biosimg, .sdimg or .uefiimg.

Defaults to ${MENDER_STORAGE_DEVICE}:rootfsa when building .ubimg.

MENDER_ROOTFS_PART_B

The partition Mender uses as the second (B) rootfs partition. See More detailed storage configuration for more information.

MENDER_ROOTFS_PART_B_NAME

See MENDER_ROOTFS_PART_A_NAME

Defaults to the value of ${MENDER_ROOTFS_PART_B} when building .biosimg, .sdimg or .uefiimg.

Defaults to ${MENDER_STORAGE_DEVICE}:rootfsb when building .ubimg.

MENDER_SERVER_URL

Variable to override the URL of the server for the client to connect to. Default value is https://docker.mender.io

MENDER_STATE_SCRIPTS

Variable to override the location of state scripts. See MENDER_STATE_SCRIPTS_DIR for more information.

MENDER_STATE_SCRIPTS_DIR

Only usable inside recipes that inherit mender-state-scripts. Recipes can put executable binaries or scripts into this location to have the scripts be included as state scripts for the Mender artifact. This should be done inside the do_compile task of a recipe.

If neither building nor other preprocessing is necessary then it is also possible to list a source archive in SRC_URI that extracts directly into ${PN}-${PV}/mender-state-scripts, where $PN and ${PV} are the usual Bitbake values of recipe name and version, respectively.

And finally, it is possible to set MENDER_STATE_SCRIPTS (note the missing _DIR) manually to a location containing state scripts, however it is recommended to use one of the two above methods.

The three methods should not be mixed.

MENDER_STORAGE_DEVICE

The storage device holding all partitions (rootfs, boot, data) used by Mender. See Configuring storage for more information.

MENDER_STORAGE_PEB_SIZE

Holds the size, in bytes, of the physical erase blocks (PEBs) on the Flash device.

MENDER_STORAGE_TOTAL_SIZE_MB

Total size of the medium that mender partitioned images will be written to, expressed in MB. The size of rootfs partition will be calculated automatically by subtracting the sizes of boot (see MENDER_BOOT_PART_SIZE_MB) and data partitions (see MENDER_DATA_PART_SIZE_MB) along with some predefined overhead (see MENDER_PARTITIONING_OVERHEAD_MB)). Default value is 1024.

MENDER_TENANT_TOKEN

Set this variable in local.conf in order to make the device recognize the organization to which it belongs. This option should always be set, except when running a custom Mender server installation with multitenancy module disabled.

MENDER_UBI_LEB_PEB_BLOCK_OVERHEAD

The overhead that each logical erase block (LEB) of the UBI device adds to the physical erase block (PEB), in bytes. In other words, how many bytes are "wasted" in each LEB. Usually set automatically, but can be overridden.

MENDER_UBI_LEB_SIZE

The size of each logical erase block (LEB) on the UBI device, in bytes. Usually set automatically from the various MENDER_UBI_*_OVERHEAD variables, but can be overridden.

MENDER_UBI_TOTAL_BAD_PEB_OVERHEAD

Total overhead on the whole UBI device, in bytes, resulting from bad physical erase blocks (PEBs). Usually zero.

MENDER_UBOOT_ENV_STORAGE_DEVICE_OFFSET

Specifies the offset from the start of the raw block storage where the U-Boot environment should be stored, expressed in bytes. The default is equal to MENDER_PARTITION_ALIGNMENT_KB (converted to bytes), and if the value is overridden, it must also be aligned to MENDER_PARTITION_ALIGNMENT_KB.

MENDER_UBOOT_POST_SETUP_COMMANDS

A set of U-Boot commands to be executed at the end of the MENDER_SETUP code in the MENDER_BOOTENV.

MENDER_UBOOT_PRE_SETUP_COMMANDS

A set of U-Boot commands to be executed at the beginning of the MENDER_SETUP code in the MENDER_BOOTENV.

MENDER_UBOOT_STORAGE_DEVICE

The storage device, as referred to by U-Boot (e.g. 1). This variable can be used in cases where the Linux kernel and U-Boot refer to the same device with different names. See The bootloader and the Linux kernel do not agree about the indexes of storage devices for more information.

MENDER_UBOOT_STORAGE_INTERFACE

The storage interface, as referred to by U-Boot (e.g. mmc). This variable can be used in cases where the Linux kernel and U-Boot refer to the same device with different names. See The bootloader and the Linux kernel do not agree about the indexes of storage devices for more information.

SYSTEMD_AUTO_ENABLE_pn-mender

Controls whether to run Mender as a systemd service. See Modes of operations and Image configuration for more information.