'YOCTO - Build partial image for application

I want to create a small application image. That image installed at a separate partition shall be mounted to /usr/local. I created a recipe like this:

inherit image
IMAGE_BASENAME = "appfs"
IMAGE_NAME_SUFFIX = ".appfs"

IMAGE_INSTALL_append = " app_lib "
IMAGE_INSTALL_append = " app_prog1 "
IMAGE_INSTALL_append = " app_prog2 "
IMAGE_INSTALL_append = " app_prog3 "

The result looks not bad, I can control the installation of the files by the prefix-Variable in the recipes of the application programms. So the will be installed in /bin, which means /usr/local/bin in the device.

But the image contains the whole directory structure of a root filesystem. Is there any comfortable way to generate the reduced directory structure of the /usr/local directory? Or do I need to clean it up by myself in a IMAGE_POSTPROCESS_COMMAND?

Kind regards

yoctoopenembedded


Solution 1:[1]

It sounds like what you want is a package or package group and not an image.

An image is a full distribution installation, usually using the poky distro. This is built-in to yocto and unavoidable, as all dependencies of your app will need to be in the image. (runtimes, supporting libs, basic linux env, etc.)

In your tmp/deploy/rpm or tmp/deploy/deb directory you should have packages related to your apps.

Something that may help organize is to create a package group to aggregate your applications.

Solution 2:[2]

If you look at your tmp/deploy/images/<machine>/<imagename>.manifest file you will notice that in addition to the packages you specified, some additional ones such as libc6 and base-files are included.

You can remove them by naming the packages in ROOTFS_RO_UNNEEDED. This variable is used to remove recipes such as shadow and run-postinsts which are processed when creating a read-only image. You can add the other undesirable recipes to this list until your manifest matches exactly the packages you want included.

For example:

# tested with Yocto 2.6
IMAGE_FSTYPES = "ext4"
IMAGE_INSTALL = "my-go-app" 
inherit image

# Don't run ldconfig on the rootfs
LDCONFIGDEPEND = ""

# If not building an RO filesystem, you can force use of ROOTFS_RO_UNNEEDED
# but be aware of the other packages included in the variable by image.bbclass 
FORCE_RO_REMOVE = "1"

# Use _append because image.bbclass includes other packages
ROOTFS_RO_UNNEEDED_append = "base-files base-files-lic \
                            bash bash-lic \
                            libc6 libc6-lic \
                            ncurses-libtinfo libtinfo5 \
                            opkg-utils-lic \
                            ncurses-terminfo-base ncurses-lic \
                            run-postinsts-lic \
                            "

The resulting filesystem I get looks like this:

tmp
??? etc
?   ??? shells.rpmsave
?   ??? timestamp
?   ??? version
??? lost+found [error opening dir]
??? usr
?   ??? bin
?   ?   ??? my-go-app
?   ??? lib
?   ?   ??? go
?   ?       ??? pkg
?   ?           ??? linux_arm64_dynlink
?   ?               ??? libstd.so
?   ??? share
?       ??? common-licenses
?       ?   ??? license.manifest
?       ??? licenses
?           ??? go-runtime
?           ?   ??? generic_BSD-3-Clause
?           ?   ??? LICENSE
?           ??? my-go-app
??? var
    ??? cache
    ??? lib

There may still be a few files left to clean up using a postprocess function:

postprocess_partial_image() {
  rm -f ${IMAGE_ROOTFS}/etc/shells.rpmsave
  rm -rf ${IMAGE_ROOTFS}/var 
}

ROOTFS_POSTPROCESS_COMMAND += "postprocess_partial_image; "

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution Source
Solution 1 mascoj
Solution 2 benf

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