This is a text-only version of the following page on https://raymii.org:

This is a text-only version of the following page on https://raymii.org:
---
Title : Execute a script in a Yocto package on every image build
Author : Remy van Elst
Date : 22-02-2022
URL : https://raymii.org/s/snippets/Execute_a_script_in_a_Yocto_package_on_every_image_build.html
Format : Markdown/HTML
---

This is a small snippet showing a Yocto recipe that executes a script on every build of an image that includes that recipe. I use it to write the build hosts date/time to a file on the image, but you could do anything you want inside the script.
It's not recommended to do this, for example, if you want to place a binary on your image you should version it correctly. Yocto can build from a git repo, no need to copy binaries. If you include the `buildinfo` class your image or the `os-release` recipe, build info is also written to your image.

In my case I had issues with the SD cards that I was using to flash the image on.
Vague errors, sometimes corruption, sometimes leftover data from a previous write,
all kinds of weird stuff. Including this recipe in my image was an extra measurement
to be sure that the SD card write succeeded, but I would not use this in an
actual production image.

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The recipe writes the current date and time to the file `/build-timestamp`. Here's how
it looks once flashed, the three commands below were each of a different image:

root@b2qt-raspberrypi4:~# cat /build-timestamp
build-timestamp-20220221181616

---

root@b2qt-raspberrypi4:~# cat /build-timestamp
build-timestamp-20220221200325

---

root@b2qt-raspberrypi4:~# cat /image-version
image-timestamp-20220221202056

---

For one reason or another, I didn't look in to in further, the `boot2qt` image
had a date/time of 2018 in `/etc/version`.

This is the recipe. I assume you know how to make your own layer and add
this recipe to, including adding it to your own image. If you include
it in your image, due to the two lines at the bottom, the script will be
executed every time that image is built.

DESCRIPTION = "Writes yocto image build datetime to image filesystem"
AUTHOR = "[email protected]"
LICENSE = "CLOSED"
PR = "r2"

S = "${WORKDIR}"

INSANE_SKIP_${PN} = "installed-vs-shipped"
FILES_${PN} += " /"

do_install() {
date_1=build-timestamp-
date_2=$(date "+%Y%m%d%H%M%S")

echo $date_1$date_2 > ${WORKDIR}/build-timestamp
install -m 0644 ${WORKDIR}/build-timestamp ${D}/build-timestamp
}

# These two lines force the recipe to be built every time.
do_compile[nostamp] = "1"
do_install[nostamp] = "1"

---

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