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		@@ -1,6 +1,6 @@
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#Service Accounts
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## Motivation 
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## Motivation
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Processes in Pods may need to call the Kubernetes API.  For example:
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  - scheduler
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@@ -20,7 +20,7 @@ They also may interact with services other than the Kubernetes API, such as:
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## Design Overview
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A service account binds together several things:
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  - a *name*, understood by users, and perhaps by peripheral systems, for an identity
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  - a *principal* that can be authenticated and (authorized)[../authorization.md]
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  - a *principal* that can be authenticated and [authorized](../authorization.md)
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  - a [security context](./security_contexts.md), which defines the Linux Capabilities, User IDs, Groups IDs, and other
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    capabilities and controls on interaction with the file system and OS.
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  - a set of [secrets](./secrets.md), which a container may use to
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@@ -60,7 +60,7 @@ This includes a human running `kubectl` on her desktop and a container in a Pod
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There is already a notion of a username in kubernetes, which is populated into a request context after authentication.
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However, there is no API object representing a user.  While this may evolve, it is expected that in mature installations,
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the canonical storage of user identifiers will be handled by a system external to kubernetes. 
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the canonical storage of user identifiers will be handled by a system external to kubernetes.
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Kubernetes does not dictate how to divide up the space of user identifier strings.  User names can be
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simple Unix-style short usernames, (e.g. `alice`), or may be qualified to allow for federated identity (
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@@ -84,7 +84,7 @@ The distinction is useful for a number of reasons:
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    - A Human typically keeps credentials on a machine that is not part of the cluster and so not subject to automatic
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      management.  A VM with a role/service-account can have its credentials automatically managed.
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  - the identity of a Pod cannot in general be mapped to a single human.
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    - If policy allows, it may be created by one human, and then updated by another, and another, until its behavior cannot be attributed to a single human.  
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    - If policy allows, it may be created by one human, and then updated by another, and another, until its behavior cannot be attributed to a single human.
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**TODO**: consider getting rid of separate serviceAccount object and just rolling its parts into the SecurityContext or
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Pod Object.
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@@ -106,7 +106,7 @@ might have some types that do not do anything on apiserver but just get pushed t
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### Pods
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The `PodSpec` is extended to have a `Pods.Spec.ServiceAccountUsername` field.  If this is unset, then a
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default value is chosen.  If it is set, then the corresponding value of `Pods.Spec.SecurityContext` is set by the
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Service Account Finalizer (see below). 
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Service Account Finalizer (see below).
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TBD: how policy limits which users can make pods with which service accounts.
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@@ -122,7 +122,7 @@ Service Account Finalizer is one place where this can happen (see below).
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### Kubelet
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The kubelet will treat as "not ready to run" (needing a finalizer to act on it) any Pod which has an empty
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SecurityContext.  
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SecurityContext.
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The kubelet will set a default, restrictive, security context for any pods created from non-Apiserver config
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sources (http, file).
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@@ -141,7 +141,7 @@ like this:
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**TODO**: example of pod with explicit refs.
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Another way is with the *Service Account Finalizer*, a plugin process which is optional, and which handles
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business logic around service accounts. 
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business logic around service accounts.
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The Service Account Finalizer watches Pods, Namespaces, and ServiceAccount definitions.
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