101 lines
3.5 KiB
Markdown
101 lines
3.5 KiB
Markdown
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Image building tools for Openstack
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==================================
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These tools are the components of tripleo (https://github.com/tripleo/demo)
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that do the plumbing involved in building disk images. Specific configs live
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in the demo repository, while the reusable tools live here.
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What tools are there?
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---------------------
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* disk-image-create -o filename {flavour} [{flavour} ...] : Create an image of
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flavour {flavour}, optionally mixing in other flavours.
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* ramdisk-image-create -o filename {flavour} [{flavour} ...] : Create a kernel+
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ramdisk pair for running maintenance on bare metal machines (deployment,
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inventory, burnin etc).
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* disk-image-get-kernel filename : Extract the appropriate kernel and ramdisk
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to use when doing PXE boot using filename as the image for a machine.
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* flavours can be found in the top level flavours directory.
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Why?
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----
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Automation: While users and operators can manually script or put together ram
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disks and disk images, mature automation makes customisation and testing easier.
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Design
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======
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Still brief - more details needed.
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Images are built using a chroot and bind mounted /proc /sys and /dev. The goal
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of the image building process is to produce blank slate machines that have all
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the necessary bits to fulfill a specific purpose in the running of an Openstack
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cloud: e.g. a nova-compute node.
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A flavour is a particular set of code that alters how the image is built, or
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runs within the chroot to prepare the image. E.g. the local-config flavour
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copies in the http proxy and ssh keys of the user running the image build
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process into the image, whereas the vm flavour makes the image build a regular
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VM image with partition table and installed grub boot sector.
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Existing flavours
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-----------------
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Flavours are found in the subdirectory flavours. Each flavour is in a directory
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named after the flavour itself. Flavours *should* have a README.md in the root
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of the flavour directory describing what it is for.
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Writing a flavour
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-----------------
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Make as many of the following subdirectories as you need, depending on what
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part of the process you need to customise:
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* block-device.d: customise the block device that the image will be made on
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(e.g. to make partitions).
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* outputs: $IMAGE\_BLOCK\_DEVICE={path}
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* inputs: $IMAGE\_BLOCK\_DEVICE={path}
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* extra-data.d: pull in extra data from the host environment that hooks may
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need during image creation. This should copy any data (such as SSH keys,
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http proxy settings and the like) somewhere under $TMP\_HOOKS\_PATH.
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* outputs: None
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* inputs: $TMP\_HOOKS\_PATH
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* pre-install.d: Run code in the chroot before customisation or packages are
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installed. A good place to add apt repositories.
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* install.d: Runs after pre-install.d in the chroot. This is a good place to
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install packages, chain into configuration management tools or do other
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image specific operations.
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* first-boot.d: Runs inside the image before rc.local. Scripts from here are
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good for doing per-instance configuration based on cloud metadata.
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Third party flavours
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--------------------
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Pending implementation. The idea is to have a search path for flavours.
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Installation
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============
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* Clone the repository locally, then add bin to your path.
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* Copy sudoers.d/\* into your /etc/sudoers.d/. (Warning, use visudo -c -f
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{filename} to check that each one parses successfully on your machine, so you
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don't break your machine).
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Invocation
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==========
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The scripts can generally just be run. Options can be set on the command line
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or by exporting variables to override those present in lib/img-defaults. -h to
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get help.
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