Embedded Linux build systems

Buildroot

• use an external layer, don’t forget to set the env variable before make my_defconfig
• build images with genimage and sign in post-image.sh
• generate configs image with in-fakeroot.sh (why? I don’t remember)
• create patches with quilt
• can have multiple rootfs_overlays, use a common base for multiple boards

override built-in package build steps in external.mk

# Strongswan TPM2 support
#STRONGSWAN_CONF_OPTS += \
#   --enable-tss-tss2=yes \
#   --enable-tpm=yes \

#STRONGSWAN_DEPENDENCIES += tpm2-tss tpm2-abrmd

# Start TPM2 abrmd before Strongswan
define TPM2_ABRMD_INSTALL_INIT_SYSV
    $(INSTALL) -D -m 0755 $(TPM2_ABRMD_PKGDIR)/S80tpm2-abrmd \
        $(TARGET_DIR)/etc/init.d/S38tpm2-abrmd
endef

Yocto

Fundamental concepts:

• Yocto always builds binary packages (package feed)
• bitbake: task scheduler (make)
• recipes: describes steps (tasks) to build a package
• virtual packages: kernel, u-boot, libc, can be provided by multiple recipes
• class: reusable tasks are described in classes
• metadata: configurations + classes + recipes, things bitbake can use to organise
• machine conf
• special recipe: image

Good for: Collecting Software BOM

Debug:

bitbake-getvar -r ncurses SRC_URI

bitbake -e ncurses

TODO: Document custom layer

Tips from kc8apf