80 lines
3.3 KiB
Plaintext
80 lines
3.3 KiB
Plaintext
=== Overview ===
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Userdata is data provided by the entity that launches an instance.
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The cloud provider makes this data available to the instance via in one
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way or anohter.
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In EC2, the data is provided by the user via the '--user-data' or
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'user-data-file' argument to ec2-run-instances. The EC2 cloud makes the
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data available to the instance via its meta-data service at
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http://169.254.169.254/latest/user-data
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cloud-init can read this input and act on it in different ways.
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=== Input Formats ===
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cloud-init will download and cache to filesystem any user-data that it
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finds. However, certain types of user-data are handled specially.
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* Gzip Compressed Content
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content found to be gzip compressed will be uncompressed, and
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these rules applied to the uncompressed data
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* Mime Multi Part archive
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This list of rules is applied to each part of this multi-part file
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Using a mime-multi part file, the user can specify more than one
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type of data. For example, both a user data script and a
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cloud-config type could be specified.
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* User-Data Script
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begins with: #! or Content-Type: text/x-shellscript
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script will be executed at "rc.local-like" level during first boot.
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rc.local-like means "very late in the boot sequence"
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* Include File
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begins with #include or Content-Type: text/x-include-url
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This content is a "include" file. The file contains a list of
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urls, one per line. Each of the URLs will be read, and their content
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will be passed through this same set of rules. Ie, the content
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read from the URL can be gzipped, mime-multi-part, or plain text
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* Include File Once
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begins with #include-once or Content-Type: text/x-include-once-url
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This content is a "include" file. The file contains a list of
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urls, one per line. Each of the URLs will be read, and their content
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will be passed through this same set of rules. Ie, the content
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read from the URL can be gzipped, mime-multi-part, or plain text
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This file will just be downloaded only once per instance, and its
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contents cached for subsequent boots. This allows you to pass in
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one-time-use or expiring URLs.
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* Cloud Config Data
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begins with #cloud-config or Content-Type: text/cloud-config
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This content is "cloud-config" data. See the examples for a
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commented example of supported config formats.
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* Upstart Job
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begins with #upstart-job or Content-Type: text/upstart-job
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Content is placed into a file in /etc/init, and will be consumed
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by upstart as any other upstart job.
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* Cloud Boothook
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begins with #cloud-boothook or Content-Type: text/cloud-boothook
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This content is "boothook" data. It is stored in a file under
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/var/lib/cloud and then executed immediately.
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This is the earliest "hook" available. Note, that there is no
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mechanism provided for running only once. The boothook must take
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care of this itself. It is provided with the instance id in the
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environment variable "INSTANCE_ID". This could be made use of to
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provide a 'once-per-instance'
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=== Examples ===
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There are examples in the examples subdirectory.
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Additionally, the 'tools' directory contains 'write-mime-multipart',
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which can be used to easily generate mime-multi-part files from a list
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of input files. That data can then be given to an instance.
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See 'write-mime-multipart --help' for usage.
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