mirror of
https://github.com/clearlinux/micro-config-drive.git
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Ikey Doherty
107 lines
3.9 KiB
Plaintext
107 lines
3.9 KiB
Plaintext
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A config-drive handler.
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====
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Contents:
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1) Description of this project
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2) Compiling, prerequisites
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3) Bugs and feedback?
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====
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Micro-config-drive ("ucd" for short) provides a subset of functionality
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that is provided by cloud-init implementations. Specifically,
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ucd provides the basic options and functions to handle config-2
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config-drive data for systems that have this config-drive data provided
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as a block device to the container or VM.
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cloud-init is the standard way for cloud customers to initialize
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containers and virtual hosts. These virtual machines are usually
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provisioned in bulk and provided without any customization to cloud
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customers, which then require that they are customized for their
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particular purpose.
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Several implementations exist that implement this functionality,
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and this implementation is fairly similar to the other ones. For
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reference, we're listing the other implementations here:
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- https://launchpad.net/cloud-init
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A Python-based implementation and the "standard". Many of the
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features of this implementation are derived and benchmarked against
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this version. This implementation supports many different OS's,
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not just Ubuntu.
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- https://github.com/coreos/coreos-cloudinit
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A Go-based implementation for CoreOS.
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While generally it's preferred to use existing implementations,
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since it reduces duplicate code and makes stronger communities, in
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this project's case it was decided to forego extending and working
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on the existing implementations. Several factors were considered, and
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a short summary of the key points of that decision are listed below.
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Speed is a significant factor. Interpreted languages have come a long
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way and are highly performant, especially if properly used. However,
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there is a significant cost of provisioning cloud nodes that have
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increased base storage costs due to the inclusion of libraries of
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interpreted languages. Since we expect people to prefer cloud nodes are
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minimal in size, having interpreted language libraries just for the
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sake of a cloud initialization script makes little sense, and we can
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reduce the storage need and copy times of cloud images significantly.
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Language choice is a minor factor. Generally languages that have
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good exception handling are preferred. Since execution speed and low
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complexity are preferred for installation and boot-time critical tasks,
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lots of libraries should be avoided, as robustness is critical. Missed
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python exceptions could cause cloud-init execution to halt, resulting
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in an unusable cloud host, which is to be avoided at all cost. The
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drawbacks of C being fairly sparse are known, and debugging tools
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compensate for that.
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We can shed additional overhead by eliminating unwanted functionality
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that a clearlinux cloud node does not need, but we can likely
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never recoup the initial cost of a base Python installation, as it
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is generally in the order of 100MB or more. Hence, we've opted to
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implement a version in C that has reduced library requrements. This
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has brought the size of this implementation down to under 1mb. Even
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considering used libraries, the resulting binary is small.
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====
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2. Compiling
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Currently, ucd requires the following prerequisites:
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- glib-2.0 >= 2.24.1
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- yaml-0.1 >= 0.1.4
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- libparted >= 3.1
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- blkid >= 2.25.0
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- json-glib-1.0
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As ucd is tooled with autotools, one shouldn't have to do
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more than:
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$ sh autogen.sh
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$ make
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$ sudo make install
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====
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3. Bugs, feedback, contact
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ucd is hosted on github. You can find releases, an issue tracker
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and git sources on github.com/clearlinux/micro-config-drive. For
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mailing lists, subscribe to dev@lists.clearlinux.org (via
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lists.clearlinux.org).
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When submitting bug reports, it may be relevant to include the
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log output of clouds- init. This can be done with the following
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command: `journalctl -b -u ucd`. Omit the `-b` option if
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you want output from prior to the last boot event.
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This project has many contributors. Not all may be mentioned in the
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AUTHORS file.
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