yocto

Question 1

How to enable the yocto build environment?

Answer 1

> source    oe-init-build-env

You will be dropped in build directory.

Question 2

How to list/show existing yocto layers?

Answer 2

> bitbake-layers  show-layers

Question 3

In yocto, how to add/remove a layer?

Answer 3

First clone the layer inside the poky directory. Then,

> bitbake-layers  add-layer  ../meta-openembedded/meta-oe

This will modify the file conf/bblayers.conf

You can also modify the conf/bblayers.conf file manually.

To remove a layer,

> bitbake-layers  remove-layer  meta-openembedded/meta-oe

Question 4

In yocto, how to find the value of a variable?

Answer 4

> bitbake-getvar  TOPDIR
> bitbake-getvar   PACKAGE_CLASSES

Question 5

In yocto, which are two most important configuration files?

Answer 5

build/conf/bblayers.conf
This contains all layers that will be used for image building.

build/conf/local.conf
We set/modify variables here.

Question 6

Name some important yocto variables.

Answer 6

• TOPDIR
• DL_DIR
• DISTRO
• PACKAGE_CLASSES
• EXTRA_IMAGE_FEATURES
• RM_OLD_IMAGE
• INHERIT

bitbake-getvar TOPDIR

Question 7

In yocto what is the relationship between a layer and recipes?

Answer 7

A layer contains many recipes. E.g., layer poky/meta contains many recipes in various subdirectories. E.g., subdir poky/meta/recipes-extended containes recipes for tar, grep, wget etc.

All recipes for a layer are contained in subdirs of that layer.

Question 8

How to list recipes in yocto?

Answer 8

> bitbake-layers   show-recipes    # lists all recipes
> bitbake-layers show-recipes  git  libxml2  # only shows info about these components.

Question 9

Name some yocto image names.

Answer 9

> bitbake  core-image-minimal
> bitbake  core-image-full-cmdline

Question 10

How to include additional software/utilities/recipes (like python3, git etc.) in a yocto image?

Answer 10

First, make sure those software/utilities are available as recipes in included layers,

> bitbake-layers   show-recipes   git  python3

If available, append following lines at the end of build/conf/local.conf file,

IMAGE_INSTALL:append  =  "   python3"
IMAGE_INSTALL:append  =  "   git"

Now build image,

> bitbake  core-image-full-cmdline

Question 11

How to create a new yocto layer?

Answer 11

> bitbake-layers  create-layer   ../meta-mylayer

> bitbake-layers  add-layer   ../meta-mylayer

Question 12

What are some recipe specific yocto variables, how to find there value?

Answer 12

• PN (Package Name)
• PV (Package Version)
• PR (Package Revision)
• S (Source code directory)
• D (Destination directory)
• SRC_URI
• WORKDIR

You can find there value for a specific recipe (e.g., libsdl2) like this,

> bitbake  -e   libsdl2  | grep ^PN=