Yocto Development with QEMU

Fetch and Configure

Let’s start by obtaining all ‘meta’ layers that we want to use recipes from. Choose a directory that you have plenty of space.

git clone --recurse-submodules \
    git@github.com:NGenetzky/meta-genet.git

We will set “TEMPLATECONF” to specify template for bblayers.conf and local.conf, and then we will source the init-build-env script to initalize a build directory.

source meta-genet/templates/set-templateconf meta-genet/templates/001-develop-with-qemu/

source meta-genet/init-build-env /data/yocto/2.4/b/build

Next we want to configure the build. The eaiest way to do this is editing build/conf/local.conf. These are a few of the things we would like configured for this build, some of them have been made in the TEMPLATECONF.

1. Set MACHINE='qemux86-64'
2. Set PACKAGE_CLASSES='package_deb'
3. Enable EXTRA_IMAGE_FEATURES = "package-management.
4. Configure mirrors for SSTATE and SOURCE.

Let’s configure where our mirrors are located. Edit the the following values to indicate where you have mirrors, such as in /data/yocto/sstate-cache/ and /data/yocto/downloads.

SSTATE_MIRRORS ?= "\
file://.* file:///data/yocto/sstate-cache/PATH \
"

SOURCE_MIRROR_URL ?= "file:///data/yocto/downloads/"

Compile

Now we will perform the actual build. Note that you must initalize the build environment before building or using scripts provided by poky.

bitbake core-image-minimal

QEMU with ext image

Then we will use qemu to run a virtual machine with the image we just built. ‘kvm’ is for performance, and ‘nographic’ and ‘serial’ causes qemu to stay in the terminal rather than launching the GUI.

runqemu \
    tmp/deploy/images/qemux86-64/core-image-minimal-qemux86-64.ext4 \
    kvm nographic serial

QEMU with NFS

Let’s make it even easier to develop on this virtual machine by running it from a NFS mount. This allows the host computer to have access to filesystem actively being used by the emulated machine. For more information read the following section of the manual: qemu-running-under-a-network-file-system-nfs-server.

This approach depends on the following target being built. Then we will extract and export the rootfs image via an NFS server.

bitbake meta-ide-support

runqemu-extract-sdk \
    build/tmp/deploy/images/qemux86-64/core-image-minimal-qemux86-64.tar.bz2 \
    nfs/core-image-minimal
runqemu-export-rootfs start \
    nfs/core-image-minimal

Finally, we run qemu with nfsroot instead of the ext4 image.

runqemu \
    nfs/core-image-minimal \
    kvm nographic serial