Disclaimer
I'm not responsible if you ruin your system, this guide functions as documentation for future me. Remember to back up your data.
Why this is useful / needed
It's useful to have a way of building a disk image for shipping, either for testing or production usage. The image output formats could be qcow2, raw or compressed tarball, it's up to you to make this what you want it to be.
Pre-work
Install diskimage-builder, for Gentoo you just have to 'emerge' the latest version. I personally keep one around in a virtual environment for testing (this allows me to build musl images as well easily).
The actual setup
What diskimage-builder actually does is take elements and run them. Each elements consists of a set of phases where the element takes actions. All you are really doing is defining the elements and they will insert themselves where needed. It also uses environment variables for tunables, or for other various small tweaks.
This is how I build the images at http://distfiles.gentoo.org/experimental/amd64/openstack/
export GENTOO_PORTAGE_CLEANUP=True
export DIB_INSTALLTYPE_pip_and_virtualenv=package
export DIB_INSTALLTYPE_simple_init=repo
export GENTOO_PYTHON_TARGETS="python3_6"
export GENTOO_PYTHON_ACTIVE_VERSION="python3.6"
export ELEMENTS="gentoo simple-init growroot vm openssh-server block-device-mbr"
export COMMAND="disk-image-create -a amd64 -t qcow2 --image-size 3"
export DATE="$(date -u +%Y%m%d)"
GENTOO_PROFILE=default/linux/amd64/17.0/no-multilib/hardened ${COMMAND} -o "gentoo-openstack-amd64-hardened-nomultilib-${DATE}" ${ELEMENTS}
GENTOO_PROFILE=default/linux/amd64/17.0/no-multilib ${COMMAND} -o "gentoo-openstack-amd64-default-nomultilib-${DATE}" ${ELEMENTS}
GENTOO_PROFILE=default/linux/amd64/17.0/hardened ${COMMAND} -o "gentoo-openstack-amd64-hardened-${DATE}" ${ELEMENTS}
GENTOO_PROFILE=default/linux/amd64/17.0/systemd ${COMMAND} -o "gentoo-openstack-amd64-systemd-${DATE}" ${ELEMENTS}
${COMMAND} -o "gentoo-openstack-amd64-default-${DATE}" ${ELEMENTS}
For musl I've had to do some custom work as I have to build the stage4s locally, but it's largely the same (with the additional need to define a musl overlay.
cd ~/diskimage-builder
cp ~/10-gentoo-image.musl diskimage_builder/elements/gentoo/root.d/10-gentoo-image
pip install -U .
cd ~/
export GENTOO_PORTAGE_CLEANUP=False
export DIB_INSTALLTYPE_pip_and_virtualenv=package
export DIB_INSTALLTYPE_simple_init=repo
export GENTOO_PYTHON_TARGETS="python3_6"
export GENTOO_PYTHON_ACTIVE_VERSION="python3.6"
DATE="$(date +%Y%m%d)"
export GENTOO_OVERLAYS="musl"
export GENTOO_PROFILE=default/linux/amd64/17.0/musl/hardened
disk-image-create -a amd64 -t qcow2 --image-size 3 -o gentoo-openstack-amd64-hardened-musl-"${DATE}" gentoo simple-init growroot vm
cd ~/diskimage-builder
git checkout diskimage_builder/elements/gentoo/root.d/10-gentoo-image
pip install -U .
cd ~/
Generic images
The elements I use are for an OpenStack image, meaning there is no default user/pass, those are set by cloud-init / glean. For a generic image you will want the following elements.
'gentoo growroot devuser vm'
The following environment variables are needed as well (changed to match your needs).
DIB_DEV_USER_PASSWORD=supersecrete DIB_DEV_USER_USERNAME=secrete DIB_DEV_USER_PWDLESS_SUDO=yes DIB_DEV_USER_AUTHORIZED_KEYS=/foo/bar/.ssh/authorized_keys
Fin
All this work was done upstream, if you have a question (or feature request) just ask. I'm on irc (Freenode) as prometheanfire or the same nick at gentoo.org for email.
