Yocto How to overwrite a file of linux rootfs depending on an IMAGE-recipe? - embedded-linux

Question

I'm trying to add a simple line in fstab within
the final rootfs that Yocto builds.
My first approach was to add my own fstab in my layer meta-mylayer/recipes-core/base-files/base-files/fstab and the proper meta-mylayer/recipes-core/base-files/base-files/base-files_%.bbappend which only have the following line:
FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
And it works, but as the title of my question says, i want to modify fstab based on the recipe-image i want to build i.e. dev-image & prod-image.
After some investigation i think i have 2 options
Modify fstab within the recipe image, extending the do_install task...
dev-image.bb
--------------
DESCRIPTION = "Development Image"
[...]
inherit core-image
do_install_append () {
echo "======= Modifying fstab ========"
cat >> ${D}${sysconfdir}/fstab <<EOF
# The line i want to Add
EOF
}
[...]
--------------
Problem is that i'm actually not seeing my modified line in my final /etc/fstab and bitbake is not showing any build error or warning about this, actually, i'm not even able to see the echo-trace i put.
My second attempt was to handle these modifications with packages and depending on the recipe-image i will be able to add the package for *-dev or *-prod. This idea was taken from Oleksandr Poznyak in this answer in summary he suggest the following:
1) Create *.bbappend recipe base-files_%s.bbappend in your layer. It
appends to poky "base-files" recipe.
2) Create your own "python do_package_prepend" function where you should
make your recipe produce two different packages
3) Add them to DEPENDS in your image recipe
And based on his example i made my own recipe:
base-files_%.bbappend
-------------------------
FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
SRC_URI += "file://fstab-dev \
file://fstab-prod \
"
PACKAGES += " ${PN}-dev ${PN}-prod"
CONFFILES_${PN}-dev = "${CONFFILES_${PN}}"
CONFFILES_${PN}-prod = "${CONFFILES_${PN}}"
pkg_preinst_${PN}-dev = "${pkg_preinst_${PN}}"
pkg_preinst_${PN}-prod = "${pkg_preinst_${PN}}"
RREPLACES_${PN}-dev = "${PN}"
RPROVIDES_${PN}-dev = "${PN}"
RCONFLICTS_${PN}-dev = "${PN}"
RREPLACES_${PN}-prod = "${PN}"
RPROVIDES_${PN}-prod = "${PN}"
RCONFLICTS_${PN}-prod = "${PN}"
python populate_packages_prepend() {
import shutil
packages = ("${PN}-dev", "${PN}-prod")
for package in packages:
# copy ${PN} content to packages
shutil.copytree("${PKGD}", "${PKGDEST}/%s" % package, symlinks=True)
# replace fstab
if package == "${PN}-dev":
shutil.copy("${WORKDIR}/fstab-dev", "${PKGDEST}/${PN}-dev/etc/fstab")
else:
shutil.copy("${WORKDIR}/fstab-prod", "${PKGDEST}/${PN}-prod/etc/fstab")
}
-------------------------
And in my recipe-image(dev-image.bb) i added base-files-dev packet
dev-image.bb
--------------
DESCRIPTION = "Development Image"
[...]
inherit core-image
IMAGE_INSTALL = " \
${MY_PACKETS} \
base-files-dev \
"
[...]
--------------
Problem with this, is that i'm not familiarized with phyton indentation so probably i'm messing things up, the error log shows as follows.
DEBUG: Executing python function populate_packages
ERROR: Error executing a python function in exec_python_func() autogenerated:
The stack trace of python calls that resulted in this exception/failure was:
File: 'exec_python_func() autogenerated', lineno: 2, function: <module>
0001:
*** 0002:populate_packages(d)
0003:
File: '/home/build/share/build_2/../sources/poky/meta/classes/package.bbclass', lineno: 1138, function: populate_packages
1134:
1135: workdir = d.getVar('WORKDIR')
1136: outdir = d.getVar('DEPLOY_DIR')
1137: dvar = d.getVar('PKGD')
*** 1138: packages = d.getVar('PACKAGES').split()
1139: pn = d.getVar('PN')
1140:
1141: bb.utils.mkdirhier(outdir)
1142: os.chdir(dvar)
File: '/usr/lib/python3.6/shutil.py', lineno: 315, function: copytree
0311: destination path as arguments. By default, copy2() is used, but any
0312: function that supports the same signature (like copy()) can be used.
0313:
0314: """
*** 0315: names = os.listdir(src)
0316: if ignore is not None:
0317: ignored_names = ignore(src, names)
0318: else:
0319: ignored_names = set()
Exception: FileNotFoundError: [Errno 2] No such file or directory: '${PKGD}'
DEBUG: Python function populate_packages finished
DEBUG: Python function do_package finished
I will really appreciate any clue or sort of direction, i'm not an Yocto expert so maybe the options that i suggest are not the most elegant and probably there is a better way to do it, so be free to give me any recommendation.
Thank you very much.
UPDATE:
As always, i was not the only one trying this, the way that i make it work was thanks this answer the only inconvenience with this is that you need to rm what you want to install through a .bbappend but for now is fine for me.
I also tried to do the same with bbclasses, which for me, it is a more elegant wayto do it, but i failed... i got the following error
ERROR: base-files-dev-3.0.14-r89 do_packagedata: The recipe base-files-dev is trying to install files into a shared area when those files already exist. Those files and their manifest location are:
I tried to rm fstab within the .bbappend but the same error is showed
Maybe somebody will share what i'm doing wrong...
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Answer 1

Your recipe which base on Oleksandr doesn't work due to dropped support for variables expansion in newer Poky.
https://www.yoctoproject.org/docs/latest/mega-manual/mega-manual.html#migration-2.1-variable-expansion-in-python-functions
Error explicit says:
Exception: FileNotFoundError: [Errno 2] No such file or directory: '${PKGD}'
It didn't expand the variable.
P.S.
This is not a proper answer to Your question but SO blocks comments.