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--- docker:docker_images_vs._container [2016/10/15 10:38] – [How to avoid image and container build-up] peter
+++ docker:docker_images_vs._container [2020/07/15 09:30] (current) – external edit 127.0.0.1
@@ Line 2: / Line 2: @@
 Docker has images and containers.  The two are closely related, but distinct.
+----
 ===== Docker Images =====
-An image is an inert, immutable, file that's essentially a snapshot of a container.  Images are created with the **[[http://docs.docker.com/reference/commandline/cli/#build|build]]** command, and they'll produce a container when started with **[[https://docs.docker.com/reference/run/|run]]**.  Images are stored in a Docker registry such as **[[https://registry.hub.docker.com/|registry.hub.docker.com]]**.  Because they can become quite large, images are designed to be composed of layers of other images, allowing a minimal amount of data to be sent when transferring images over the network.
+Images are basically a template used to create containers.
-Local images can be listed by running docker images:
+  * An image is an inert, immutable, file that's essentially a snapshot of a container.
+  * Images are created with the **[[http://docs.docker.com/reference/commandline/cli/#build|build]]** command, and they'll produce a container when started with **[[https://docs.docker.com/reference/run/|run]]**.
+  * Images are stored in a Docker registry such as **[[https://registry.hub.docker.com/|registry.hub.docker.com]]**.
+  * Because they can become quite large, images are designed to be composed of layers of other images, allowing a minimal amount of data to be sent when transferring images over the network.
-<code>
+Local images can be listed by running:
+<code bash>
+docker images
+</code>
+returns:
+<code bash>
 REPOSITORY                TAG                 IMAGE ID            CREATED             VIRTUAL SIZE
 ubuntu                    13.10               5e019ab7bf6d        2 months ago        180 MB
@@ Line 30: / Line 43: @@
 More info on images is available from the [[https://docs.docker.com/terms/image/|Docker docs]].
+----
 ===== Docker Containers =====
-To use a programming metaphor, if an image is a class, then a container is an instance of a class—a runtime object.  Containers are hopefully why you're using Docker; they're lightweight and portable encapsulations of an environment in which to run applications.
+To use a programming metaphor, if an image is a class, then a container is an instance of a class — a runtime object.
-View local running containers with **docker ps**:
+Containers are hopefully why you're using Docker; they're lightweight and portable encapsulations of an environment in which to run applications.
-<code>
+View local running containers by running:
+<code bash>
+docker ps
+</code>
+returns:
+<code bash>
 CONTAINER ID        IMAGE                               COMMAND                CREATED             STATUS              PORTS                    NAMES
 f2ff1af05450        samalba/docker-registry:latest      /bin/sh -c 'exec doc   4 months ago        Up 12 weeks         0.0.0.0:5000->5000/tcp   docker-registry
@@ Line 48: / Line 70: @@
   - **NAMES** can be used to identify a started container via the **<nowiki>--name</nowiki>** flag.
+----
 ===== How to avoid image and container build-up =====
-There's a constant build-up of untagged images and stopped containers - which could lead to a maxed out hard drive.
+There's a constant build-up of untagged images and stopped containers which could lead to a maxed out hard drive.
 We can remove all untagged images by combining **docker rmi** with the recent **dangling=true** query:
@@ Line 65: / Line 88: @@
 </code>
-These are known pain points with Docker, and may be addressed in future releases.  However, with a clear understanding of images and containers, these situations can be avoided with a couple of practices:
+These are known pain points with Docker, and may be addressed in future releases.
-  - Always remove a useless, stopped container with docker rm [CONTAINER_ID].
+However, with a clear understanding of images and containers, these situations can be avoided with a couple of practices:
-  - Always remove the image behind a useless, stopped container with docker rmi [IMAGE_ID].
+  - Always remove a useless, stopped container with **docker rm [CONTAINER_ID]**.
+  - Always remove the image behind a useless, stopped container with **docker rmi [IMAGE_ID]**.