Isolated application execution with Docker
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Image
An image is the basis for a container and includes only its program code
and basic settings.
It does not include information the program code generates on a storage
medium or RAM while it is running.
Moreover, it does not include any information on the environment the image
is to be executed in, i.e. it is platform-neutral.
An image always relates to the defined processor architecture it is compiled
for, e.g. x86, x64 or ARM. If a container is generated from an image, make
sure that the image is suitable for the hardware platform used.
For distributing images via the Internet, the Docker organization provides a
so-called repository under
https://hub.docker.com/
. Images stored there
are freely accessible. Users can also manage their own repositories.
Note:
For more information on images, see the Docker documentation
https://docs.docker.com/engine/docker-overview/%23docker-
objects
and, in particular, its glossary
https://docs.docker.com/
glossary/?term=image
.
Container
A container is a runtime instance of an image.
A container represents an image that is being executed in its individual
runtime environment and can be compared with a running process.
Running an image in a container is commonly denominated as "starting"
the container. The term "starting" implies that Docker transfers the image to
an individual runtime environment to execute it there. This runtime
environment is isolated against host machine and other containers, i.e.
neither host machine nor other containers can influence it. Access to
resources of the host system as e.g. host files and ports occurs only if
explicitly configured.
A container consists of:
·
a Docker image,
·
a runtime environment, and
·
a standard command architecture.
The runtime environment contains e.g. current information on configuration
and status. For storing this information, Docker generates a virtual drive in
the container, a so-called "volume"
Docker can start several containers, even containers originating from the
same image.
netPI | NOIT-E-NPI3-51-EN-RE
DOC170801UM01EN | Revision 1 | English | 2017-09 | Released | Public
© Hilscher 2017
