1.11. Image MetaData (IMD)

barebox images can be enriched with metadata. This is useful to get information the board an image is compiled for and which barebox version an image contains.

There are predefined tags for:

  • The build timestamp

  • The barebox release version

  • The model (board) the image is compiled for

  • The toplevel device tree compatible properties the image can handle

Additionally there is a generic key/value tag to add information which does not fit into the above categories, for example the memory size for boards which come with different memory sizes which can’t be automatically detected.

The informations can be extracted with the bareboximd tool which lives under scripts/ in the barebox sourcecode. If enabled it is compiled for the compile host and also for the target architecture. barebox itself has the imd - extract metadata from barebox binary command to extract the informations. Here is an example output of the tool called without additional options:

# imd barebox-phytec-pbab01dl-1gib.img
build: #890 Wed Jul 30 16:15:24 CEST 2014
release: 2014.07.0-00167-ge6632a9-dirty
parameter: memsize=1024
of_compatible: phytec,imx6x-pbab01 phytec,imx6dl-pfla02 fsl,imx6dl
model: Phytec phyFLEX-i.MX6 Duallite Carrier-Board

Single informations can be extracted with the -t <type> option:

# imd barebox-phytec-pbab01dl-1gib.img -t release
2014.07.0-00167-ge6632a9-dirty

Since the barebox hush does not have output redirection the barebox too has the -s <var> option to assign the output to a variable for later evaluation.

1.11.1. Limitations

The IMD tags are generated in the barebox binary before a SoC specific image is generated. Some SoCs encrypt or otherwise manipulate the images in a way that the IMD information is lost. The IMD mechanism does not work on these SoCs. A known example is the Freescale i.MX28.

1.11.2. IMD and barebox_update

The IMD information can be used to check if an image is suitable for updating barebox for a particular board. This is done by comparing the OF compatible of the running barebox image against the compatible tags in the barebox binary being installed.