systemd-sysext can load a raw-image containing usr/ and opt/ folders to mount them as RO overlay over the rootfs, to "extend" the systems.
This class provides the necessary changes/additions to the enclosed file-system so that systemd-sysext accepts the extension for "merge" into the rootfs. With such an created image, placed into the correct folder (see [1]), `systemd-sysext list` should be able to list the "extension" and `systemd-sysext merge` should enable the overlay. On both commands a preceding "SYSTEMD_LOG_LEVEL=debug" can aide in figuring out what is amiss. The strict name checking systemd-sysext does against the name of extension-release.NAME file, is disabled, as there is only one such in the resulting image. This is done to allow a user to freely rename the resulting image file. Note that for e.g. squashfs, the kernel needs CONFIG_SQUASHFS_XATTR=y Link: https://www.freedesktop.org/software/systemd/man/latest/systemd-sysext.html Link: https://0pointer.net/blog/testing-my-system-code-in-usr-without-modifying-usr.html Signed-off-by: Johannes Schneider <johannes.schnei...@leica-geosystems.com> --- meta/classes-recipe/image-sysext.bbclass | 42 ++++++++++++++++++++++++ 1 file changed, 42 insertions(+) create mode 100644 meta/classes-recipe/image-sysext.bbclass diff --git a/meta/classes-recipe/image-sysext.bbclass b/meta/classes-recipe/image-sysext.bbclass new file mode 100644 index 0000000000..012db83353 --- /dev/null +++ b/meta/classes-recipe/image-sysext.bbclass @@ -0,0 +1,42 @@ +# SPDX-License-Identifier: MIT +# +# Copyright Leica Geosystems AG +# + +# systemd-sysext [1] has a simple mechanism for version compatibility: +# the extension to be loaded has to contain a +# /usr/lib/extension-release.d/extension-release.NAME +# with "NAME" *exactly* matching the filename of the extensions +# raw-device filename/ +# +# from the extension-release file the "ID" and "VERSION_ID" fields are +# matched against the etc/os-release and the extension is only "merged" +# if no mismatches between NAME, ID, and VERSION_ID. +# +# Link: https://www.freedesktop.org/software/systemd/man/latest/systemd-sysext.html + +inherit image + +IMAGE_NAME_SUFFIX = ".sysext" +EXTENSION_NAME = "${IMAGE_NAME}${IMAGE_NAME_SUFFIX}.${IMAGE_FSTYPES}" + +DEPENDS += " os-release" + +sysext_image_mangle_rootfs() { + R=${IMAGE_ROOTFS} + + # pull a copy of the rootfs version information, which systemd-sysext matches against + cp -av ${RECIPE_SYSROOT}/${nonarch_libdir}/os-release ${WORKDIR}/extension-release.base + + echo 'EXTENSION_RELOAD_MANAGER=1' >> ${WORKDIR}/extension-release.base + + install -d $R${nonarch_libdir}/extension-release.d + install -m 0644 ${WORKDIR}/extension-release.base \ + $R${nonarch_libdir}/extension-release.d/extension-release.${EXTENSION_NAME} + + # disable systemd-sysext's strict name checking, so that the image file can be renamed, while still being 'merge'-able + setfattr -n user.extension-release.strict -v false \ + $R${nonarch_libdir}/extension-release.d/extension-release.${EXTENSION_NAME} +} + +ROOTFS_POSTPROCESS_COMMAND += " sysext_image_mangle_rootfs; " -- 2.34.1
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