Building in a Self-Contained Environment



Users building images with KIWI NG face problems if they want to build an image matching one of the following criteria:

  • build should happen as non root user.

  • build should happen on a host system distribution for which no KIWI NG packages exists.

  • build happens on an incompatible host system distribution compared to the target image distribution. For example building an apt/dpkg based system on an rpm based system.

  • run more than one build process at the same time on the same host.

  • run a build process for a different target architecture compared to the host architecture (Cross Arch Image Build)

This document describes how to perform the build process in a self contained environment using fast booting virtual machines to address the issues listed above.

The changes on the machine to become a build host will be reduced to the requirements of the KIWI NG boxed plugin


Add the KIWI NG repo from the Open Build Service. For details see Installation from OBS. The following KIWI NG plugin needs to be installed on the build system:

$ sudo zypper in python3-kiwi_boxed_plugin

Building with the boxbuild command

The installation of the KIWI NG boxed plugin has registered a new kiwi command named boxbuild. The command implementation uses KVM as virtualization technology and runs the KIWI NG build command inside of a KVM controlled virtual machine. For running the build process in a virtual machine it’s required to provide VM images that are suitable to perform this job. We call the VM images boxes and they contain kiwi itself as well as all other components needed to build appliances. Those boxes are hosted in the Open Build Service and are publicly available at the Subprojects tab in the: Virtualization:Appliances:SelfContained project.

As a user you don’t need to work with the boxes because this is all done by the plugin and provided as a service by the KIWI NG team. The boxbuild command knows where to fetch the box and also cares for an update of the box when it has changed.

Building an image with the boxbuild command is similar to building with the build command. The plugin validates the given command call with the capabilities of the build command. Thus one part of the boxbuild command is exactly the same as with the build command. The separation between boxbuild and build options is done using the -- separator like shown in the following example:

$ kiwi-ng --type iso system boxbuild --box leap -- \
      --description kiwi/build-tests/x86/leap/test-image-disk \
      --set-repo obs://openSUSE:Leap:15.5/standard \
      --target-dir /tmp/myimage


The provided --description and --target-dir options are setup as shared folders between the host and the box. No other data will be shared with the host.

Sharing Backends

As mentioned above, the boxbuild call shares the two host directories provided in --description and --target-dir with the box. To do this the following sharing backends are supported:


With QEMU’s 9pfs you can create virtual filesystem devices (virtio-9p-device) and expose them to the box. For more information see 9pfs. Using this sharing backend does not require any setup procedure from the user and is also the default for boxbuild


SSHFS is a FUSE-based filesystem client for mounting remote directories over a Secure Shell connection (SSH). In boxbuild this is used to mount directories from the host into the box. Because this runs through an SSH connection the host must allow connections from the box. If you plan to use sshfs add the following SSH public key to the ~/.ssh/authorized_keys file of the user which is expected to call boxbuild

echo "ssh-rsa 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 kiwi@boxbuild" >> ~/.ssh/authorized_keys

The public key mentioned here is associated with an SSH key pair we provide in the pre-built box images.


If the sshfs backend is used without the host trusting the box, the boxbuild call will become interactive at the time of the sshfs mount. In this case the user might be asked for a passphrase or depending on the host sshd setup the request will be declined and the boxbuild fails.


QEMU virtio-fs shared file system daemon. Share a host directory tree with a box through a virtio-fs device. For more information see virtiofs. Using this sharing backend does not require any setup procedure from the user


virtiofs support was added but considered experimental and not yet stable across the distributions. Feedback welcome.