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Docker 101: container start and cleanup

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B. van Berkum 2017-10-03 00:24:23 +02:00
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doc/md/docker/docker-101.md
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@ -60,3 +60,40 @@ wheezy: Pulling from debian
Digest: sha256:c584131da2ac1948aa3e66468a4424b6aea2f33acba7cec0b631bdb56254c4fe Digest: sha256:c584131da2ac1948aa3e66468a4424b6aea2f33acba7cec0b631bdb56254c4fe
Status: Downloaded newer image for debian:wheezy Status: Downloaded newer image for debian:wheezy
``` ```
Docker re-uses layers already downloaded. Iow. if you have only images based on some Alpine or Ubuntu version for example, those can share disk space.
### Start a container
A container is an instance created from an image, that can be run and that keeps running until its main process exits. Or until the user stops the container.
The simplest way to start a container from image is ``docker run``. It also pulls the image for you if it is not locally available. For more advanced use, refer to ``docker create``.
Note that stopped containers are not destroyed, unless you specify ``--rm``.
To view all created, running and stopped containers, enter:
```bash
$ docker ps -a
```
Some containers may be designed or configured to be restarted, others are not. Note that both network ports and volumes of a container are created on start, and not editable later.
### Access a running container
A running container is accessible using ``docker exec``, or ``docker copy``.
You can use ``exec`` to start a root shell in the Shaarli container:
```bash
$ docker exec -ti <container-name-or-id> bash
```
Note the names and ID's of containers are list in ``docker ps``. You an even type only one or two letters of the ID, given they are unique.
Access can also be through one or more network ports, or disk volumes. Both are specified on and fixed on ``docker create`` or ``run``.
### Docker disk use
Trying out different images can fill some gigabytes of disk quickly. Besides images, the docker volumes usually take up most disk space.
If you care only about trying out docker and not about what is running or saved,
the following commands should help you out quickly:
```bash
$ docker rmi -f $(docker images -aq) # remove or mark all images for disposal
$ docker volume rm $(docker volume ls -q) # remove all volumes
```