Create a New Meta Layer and Write a Hello World Recipe in Yocto Project.

In this tutorial, you will learn how to create a new meta-layer and how to write a new hello world bitbake recipe in the Yocto Project. We will build the image with the hello recipe for QEMU and verify this package present in the rootfs.

1-Create a new meta layer and add it to bblayer.conf file

• Yocto provides a tool that can create the meta-layer and maintain the directory structure which Yocto Project supports.
• Run the below command to create a new layer.

$ cd poky
$ source oe-init-build-env
# Now, build folder would your current working directory.

$ bitbake-layers create-layer ../meta-tutorial
# This command creates the meta-tutorial layer inside the poky directory. 

# Add this layer into bblayer.conf file
$ bitbake-layers add-layer ../meta-tutorial

# Display all layer present in the bblayer.conf file. 
$ bitbake-layers show-layers

2-Create Directory For Recipe and Source Files

• Our meta tutorial layer directory structure looks like this.

• We need to create a hello and files directory at the below location.
• poky/meta-tutorial/recipe-example/hello
• poky/meta-tutorial/recipe-example/hello/files/

3-Write the simple hello world c program

Create the hello.c file at the poky/meta-tutorial/recipe-example/hello/files/hello.c

//Simple Hello World Program 
#include<stdio.h>
int main() { 
printf("Hello World , Created Bitbake recipe successfully\n"); 
return 0;
}

4-Write the simple hello recipe file

Create hello_1.0.bb recipe file at the poky/meta-tutorial/recipe-example/hello/hello_1.0.bb

DESCRIPTION = "Simple helloworld application"
LICENSE = "MIT"
LIC_FILES_CHKSUM = "file://${COMMON_LICENSE_DIR}/MIT;md5=0835ade698e0bcf8506ecda2f7b4f302"

SRC_URI = "file://hello.c"

S = "${WORKDIR}"

do_compile() {
        ${CC} hello.c ${LDFLAGS} -o hello
}

do_install() {
        install -d ${D}${bindir}
        install -m 0755 hello ${D}${bindir}
}

Reference: Hello recipe

• This hello recipe fetch the source file( hello.c) using the SRC_URI variable and do_compile used to compile the hello.c source file and generated the hello binary.
• do_install function install hello binary at the /usr/bin of the target rootfs.
• Now, the latest directory looks like this.

5-Select machine configuration and Add hello package to rootsfs

We are building an image for machine QEMUx86-64 so we have to add this machine in conf/local.conf file.

#By default, this machine selection is enabled. 
MACHINE ??= "qemux86-64" 

#We need to add the hello software package to the target image 
IMAGE_INSTALL_append = " hello"

6-Build Image

Run bitbake to build the minimal boot image for QEMU.

$bitbake core-minimal-image

7-Run the QEMU image and verify the installed Package

Use the below command to run the QEMU image on Your host PC.

$runqemu qemux86-64

We installed the hello package at /usr/bin so run hello from the terminal and it gives the output.

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