@@ -23,129 +23,135 @@ Services, Deployments, and Builds for delivering changes.
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.PP
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Concepts:
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- .IP \n+ [ step ]
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- \i tem
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.PP
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+ .RS
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+ .nf
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Containers:
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A definition of how to run one or more processes inside of a portable Linux
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environment. Containers are started from an Image and are usually isolated
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from other containers on the same machine.
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- \i tem
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- .PP
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Image:
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A layered Linux filesystem that contains application code, dependencies,
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and any supporting operating system libraries. An image is identified by
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a name that can be local to the current cluster or point to a remote Docker
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registry (a storage server for images).
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- \i tem
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- .PP
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Pods [pod]:
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A set of one or more containers that are deployed onto a Node together and
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share a unique IP and Volumes (persistent storage). Pods also define the
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security and runtime policy for each container.
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- \i tem
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- .PP
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Labels:
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Labels are key value pairs that can be assigned to any resource in the
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system for grouping and selection. Many resources use labels to identify
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sets of other resources.
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- \i tem
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- .PP
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Volumes:
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Containers are not persistent by default \- on restart their contents are
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cleared. Volumes are mounted filesystems available to Pods and their
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containers which may be backed by a number of host\- local or network
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attached storage endpoints. The simplest volume type is EmptyDir, which
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is a temporary directory on a single machine. Administrators may also
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allow you to request a Persistent Volume that is automatically attached
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to your pods.
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- \i tem
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- .PP
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Nodes [node]:
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Machines set up in the cluster to run containers. Usually managed
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by administrators and not by end users.
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- \i tem
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- .PP
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Services [svc]:
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A name representing a set of pods (or external servers) that are
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accessed by other pods. The service gets an IP and a DNS name, and can be
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exposed externally to the cluster via a port or a Route. It's also easy
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to consume services from pods because an environment variable with the
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name <SERVICE>\_ HOST is automatically injected into other pods.
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- \i tem
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- .PP
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Routes [route]:
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A route is an external DNS entry (either a top level domain or a
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dynamically allocated name) that is created to point to a service so that
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it can be accessed outside the cluster. The administrator may configure
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one or more Routers to handle those routes, typically through an Apache
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or HAProxy load balancer / proxy.
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- .PP
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Replication Controllers [rc]:
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A replication controller maintains a specific number of pods based on a
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template that match a set of labels. If pods are deleted (because the
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node they run on is taken out of service) the controller creates a new
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copy of that pod. A replication controller is most commonly used to
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represent a single deployment of part of an application based on a
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built image.
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- .PP
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Deployment Configuration [dc]:
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Defines the template for a pod and manages deploying new images or
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configuration changes whenever those change. A single deployment
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configuration is usually analogous to a single micro\- service. Can support
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many different deployment patterns, including full restart, customizable
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rolling updates, and fully custom behaviors, as well as pre\- and post\-
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hooks. Each deployment is represented as a replication controller.
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- .PP
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Build Configuration [bc]:
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Contains a description of how to build source code and a base image into a
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new image \- the primary method for delivering changes to your application.
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Builds can be source based and use builder images for common languages like
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Java, PHP, Ruby, or Python, or be Docker based and create builds from a
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Dockerfile. Each build configuration has web\- hooks and can be triggered
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automatically by changes to their base images.
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- .PP
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Builds [build]:
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Builds create a new image from source code, other images, Dockerfiles, or
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binary input. A build is run inside of a container and has the same
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restrictions normal pods have. A build usually results in an image pushed
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to a Docker registry, but you can also choose to run a post\- build test that
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does not push an image.
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- .PP
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Image Streams and Image Stream Tags [is,istag]:
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An image stream groups sets of related images under tags \- analogous to a
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branch in a source code repository. Each image stream may have one or
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more tags (the default tag is called "latest") and those tags may point
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at external Docker registries, at other tags in the same stream, or be
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controlled to directly point at known images. In addition, images can be
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pushed to an image stream tag directly via the integrated Docker
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registry.
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- .PP
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Secrets [secret]:
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The secret resource can hold text or binary secrets for delivery into
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your pods. By default, every container is given a single secret which
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contains a token for accessing the API (with limited privileges) at
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/var/run/secrets/kubernetes.io/serviceaccount. You can create new
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secrets and mount them in your own pods, as well as reference secrets
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from builds (for connecting to remote servers) or use them to import
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remote images into an image stream.
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Projects [project]:
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All of the above resources (except Nodes) exist inside of a project.
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Projects have a list of members and their roles, like viewer, editor,
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or admin, as well as a set of security controls on the running pods, and
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limits on how many resources the project can use. The names of each
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resource are unique within a project. Developers may request projects
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be created, but administrators control the resources allocated to
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projects.
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+ .fi
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+ .RE
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.PP
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For more, see
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\[la ] https://docs.openshift.com\[ra ]
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