Build all packages for an image - yocto

Question

Is it possible to build all of the packages for a specific image? I know I can build packages individually, but ideally would like to build all of them at once, through a single command.
Alternatively, is there a way to prevent the do_rootfs task from being executed for a particular image.
Cheers, Donal

Answer 1

First make an image that contains a packagegroup (or just list your dependencies there).
$ cat sources/meta-custom/recipes-custom/images/only-packages-image.bb
SUMMARY = "All dependencies no image"
LICENSE = "CLOSED"
version = "##DISTRO_VERSION##"
BB_SCHEDULER = "speed"
# option 1 - packagegroup, package list can be reused in real image
CORE_IMAGE_BASE_INSTALL += "\
packagegroup_all-depends \
"
# option 2 - list deps here, package list can not be reused in real image
CORE_IMAGE_BASE_INSTALL += "\
lshw \
systemd \
cronie \
glibc \
sqlite \
bash \
python3-dev \
python3-2to3 \
python3-misc \
python3-pyvenv \
python3-modules \
python3-pip \
wget \
apt \
pciutils \
file \
tree \
\
wpa-supplicant \
dhcpcd \
networkmanager \
curl-dev \
curl \
hostapd \
iw \
"
# remove the rootfs step
do_rootfs() {
}
Second make your packagegroup if you opted to reuse the list of packages
$ cat sources/meta-custom/recipes-custom/packagegroups/packagegroup-alldeps.bb
PACKAGE_ARCH = "${MACHINE_ARCH}"
inherit packagegroup
RDEPENDS_${PN} = " \
lshw \
systemd \
cronie \
glibc \
sqlite \
bash \
python3-dev \
python3-2to3 \
python3-misc \
python3-pyvenv \
python3-modules \
python3-pip \
wget \
apt \
pciutils \
file \
tree \
\
wpa-supplicant \
dhcpcd \
networkmanager \
curl-dev \
curl \
hostapd \
iw \
"
Finally build your new image placeholder
$ bitbake only-packages-image

Answer 2

In Yocto >=4.0 this is actually pretty easy to achieve. The packagegroup method did not work for me at all.
I don't know if this works in older versions though.
Create a new file in your custom layer, e.g. meta-custom/classes/norootfs.bbclass and put the following lines in there (as far as I noticed the order does not matter):
deltask do_deploy
deltask do_image
deltask do_rootfs
deltask do_image_complete
deltask do_image_setscene
then in your meta-custom/recipes-core/images/myimage.bb add norootfs to your other inherit commands
e.g. the most basic one
inherit core-image norootfs
You will notice your number of tasks decreasing by a fair amount (mine from ~4700 to ~3000) and there is no complete rootfs image anymore in build/tmp/deploy/images, except for bzImage and modules, just the plain ipk files in build/tmp/deploy/ipk.
I got this information by looking at https://docs.yoctoproject.org/ref-manual/tasks.html?highlight=do_image and .bbclass files in meta/classes where deltask is frequently used.