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This package handles meta and user data for different cloud and other platforms. It should be easy to extend to new platforms. Currently, it handles GCP metadata and a simple CDROM userdata provider. Signed-off-by: Rolf Neugebauer <rolf.neugebauer@docker.com>
71 lines
2.1 KiB
Markdown
71 lines
2.1 KiB
Markdown
# Metadata and Userdata handling
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Most providers offer a mechanism to provide a OS with some additional
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metadata as well as custom userdata. `Metadata` in this context is
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fixed information provided by the provider (e.g. the host
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name). `Userdata` is completely custom data which a user can supply to
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the instance.
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The [metadata package](../pkg/metadata/) handles both metadata and
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userdata for a number of providers (see below). It abstracts over the
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provider differences by exposing both metadata and userdata in a
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directory hierarchy under `/var/config`. For example, sshd config
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files from the metadata are placed under `/var/config/ssh`.
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Userdata is assumed to be a single string and the contents will be
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stored under `/var/config/userdata`. If userdata is a json file, the
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contents will be further processed, where different keys cause
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directories to be created and the directories are populated with files. Foer example, the following userdata file:
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```
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{
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"ssh" : {
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"sshd_config" : {
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"perm" : "0600",
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"content": "PermitRootLogin yes\nPasswordAuthentication no"
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}
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},
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"foo" : {
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"bar" : {
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"perm": "0644",
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"content": "foobar"
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},
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"baz" : {
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"perm": "0600",
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"content": "bar"
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}
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}
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}
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```
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will generate the following files:
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```
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/var/config/ssh/sshd_config
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/var/config/foo/bar
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/var/config/foo/baz
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```
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This hierarchy can then be used by individual containers, who can bind
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mount the config sub-directory into their namespace where it is
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needed.
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# Providers
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Below is a list of supported providers and notes on what is supported. We will add more over time.
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## GCP
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GCP metadata is reached via a well known URL
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(`http://metadata.google.internal/`) and currently
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we extract the hostname and populate the
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`/var/config/ssh/authorized_keys` from metadata. In the future we'll
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add more complete SSH support.
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GCP userdata is extracted from `/computeMetadata/v1/instance/attributes/userdata`.
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## HyperKit
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HyperKit does not support metadata and userdata is passed in as a single file via a ISO9660 image.
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