mirror of
https://github.com/moby/moby.git
synced 2022-11-09 12:21:53 -05:00
47 lines
1.7 KiB
ReStructuredText
47 lines
1.7 KiB
ReStructuredText
:title: Container
|
|
:description: Definitions of a container
|
|
:keywords: containers, lxc, concepts, explanation, image, container
|
|
|
|
.. _container_def:
|
|
|
|
Container
|
|
=========
|
|
|
|
.. image:: images/docker-filesystems-busyboxrw.png
|
|
|
|
Once you start a process in Docker from an :ref:`image_def`, Docker
|
|
fetches the image and its :ref:`parent_image_def`, and repeats the
|
|
process until it reaches the :ref:`base_image_def`. Then the
|
|
:ref:`ufs_def` adds a read-write layer on top. That read-write layer,
|
|
plus the information about its :ref:`parent_image_def` and some
|
|
additional information like its unique id, networking configuration,
|
|
and resource limits is called a **container**.
|
|
|
|
.. _container_state_def:
|
|
|
|
Container State
|
|
...............
|
|
|
|
Containers can change, and so they have state. A container may be
|
|
**running** or **exited**.
|
|
|
|
When a container is running, the idea of a "container" also includes a
|
|
tree of processes running on the CPU, isolated from the other
|
|
processes running on the host.
|
|
|
|
When the container is exited, the state of the file system and
|
|
its exit value is preserved. You can start, stop, and restart a
|
|
container. The processes restart from scratch (their memory state is
|
|
**not** preserved in a container), but the file system is just as it
|
|
was when the container was stopped.
|
|
|
|
You can promote a container to an :ref:`image_def` with ``docker
|
|
commit``. Once a container is an image, you can use it as a parent for
|
|
new containers.
|
|
|
|
Container IDs
|
|
.............
|
|
All containers are identified by a 64 hexadecimal digit string (internally a 256bit
|
|
value). To simplify their use, a short ID of the first 12 characters can be used
|
|
on the commandline. There is a small possibility of short id collisions, so the
|
|
docker server will always return the long ID.
|