John L. Villalovos 14e7cb3eb2 Update doc to have 'debootstrap' dep and describe minimal

Update the doc, that explains how to use disk-image-builder to create an
image, to have an additional dependency on 'debootstrap'

Also remove DISTRO= line from example as it was confusing and would make
people not build the ubuntu-minimal image.

Add a little info on the -minimal build types.

Change-Id: I8a7393a9c71ef503a730e4442941996eab43da6b

2016-10-12 19:27:05 -07:00

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Using diskimage-builder to build devstack-gate nodes

In addition to being able to just download and consume images that are the same as what run devstack-gate, it's easy to make your own for local dev or testing - or just for fun.

Install diskimage-builder

Install the dependencies:

sudo apt-get install kpartx qemu-utils curl python-yaml debootstrap

Install diskimage-builder:

sudo -H pip install diskimage-builder

Build an image

Building an image is simple, we have a script!

bash tools/build-image.sh

See the script for environment variables to set distribution, etc. By default it builds an ubuntu-minimal based image. You should be left with a .qcow2 image file of your selected distribution.

Infra uses the -minimal build type for building Ubuntu/CentOS/Fedora. For example: ubuntu-minimal.

It is a good idea to set TMP_DIR to somewhere with plenty of space to avoid the disappointment of a full-disk mid-way through the script run.

While testing, consider exporting DIB_OFFLINE=true, to skip updating the cache.

Mounting the image

If you would like to examine the contents of the image, you can mount it on a loopback device using qemu-nbd.

sudo apt-get install qemu-utils
sudo modprobe nbd max_part=16
sudo mkdir -p /tmp/newimage
sudo qemu-nbd -c /dev/nbd1 /path/to/devstack-gate-precise.qcow2
sudo mount /dev/nbd1p1 /tmp/newimage

or use the scripts

sudo apt-get install qemu-utils
sudo modprobe nbd max_part=16
sudo tools/mount-image.sh devstack-gate-precise.qcow2
sudo tools/umount-image.sh

Other things

It's a qcow2 image, so you can do tons of things with it. You can upload it to glance, you can boot it using kvm, and you can even copy it to a cloud server, replace the contents of the server with it and kexec the new kernel.

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