Probably Done Before: Visualizing Docker Containers and Images - 0 views
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In my opinion, understanding how a technology works under the hood is the best way to achieve learning speed and to build confidence that you are using the tool in the correct way.
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union view
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The top-level layer may be read by a union-ing file system (AUFS on my docker implementation) to present a single cohesive view of all the changes as one read-only file system
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it is nearly the same thing as an image, except that the top layer is read-write
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A container is defined only as a read-write layer atop an image (of read-only layers itself). It does not have to be running.
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a running container
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the the isolated process-space and processes within
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A running container is defined as a read-write "union view" and
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kernel-level technologies like cgroups, namespaces
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The processes within this process-space may change, delete or create files within the "union view" file that will be captured in the read-write layer
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there is no longer a running container
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each layer contains a pointer to a parent layer using the Id
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The 'docker create' command adds a read-write layer to the top stack based on the image id. It does not run this container.
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The command 'docker start' creates a process space around the union view of the container's layers.
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can only be one process space per container.
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the docker run command starts with an image, creates a container, and starts the container
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'git pull' (which is a combination of 'git fetch' and 'git merge')
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'docker ps' lists out the inventory of running containers on your system
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'docker ps -a' where the 'a' is short for 'all' lists out all the containers on your system, whether stopped or running.
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Only those images that have containers attached to them or that have been pulled are considered top-level.
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'docker stop' issues a SIGTERM to a running container which politely stops all the processes in that process-space.
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results is a normal, but non-running, container
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'docker kill' issues a non-polite SIGKILL command to all the processes in a running container.
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'docker stop' and 'docker kill' which send actual UNIX signals to a running process
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'docker pause' uses a special cgroups feature to freeze/pause a running process-space
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'docker rm' removes the read-write layer that defines a container from your host system
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It effectively deletes files
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'docker rmi' removes the read-layer that defines a "union view" of an image.
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'docker commit' takes a container's top-level read-write layer and burns it into a read-only layer.
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turns a container (whether running or stopped) into an immutable image
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uses the FROM directive in the Dockerfile file as the starting image and iteratively 1) runs (create and start) 2) modifies and 3) commits.
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At each step in the iteration a new layer is created.
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'docker exec' command runs on a running container and executes a process in that running container's process space
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'docker inspect' fetches the metadata that has been associated with the top-layer of the container or image
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'docker save' creates a single tar file that can be used to import on a different host system
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only be run on an image
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'docker export' command creates a tar file of the contents of the "union view" and flattens it for consumption for non-Docker usages
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This command removes the metadata and the layers. This command can only be run on containers.
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'docker history' command takes an image-id and recursively prints out the read-only layers
