Container

TL;DR

Lifecycle

docker create creates a container but does not start it.
docker rename allows the container to be renamed.
docker run creates and starts a container in one operation.
docker rm deletes a container.
docker update updates a container’s resource limits.

Starting and stpping

docker start starts a container so it is running.
docker stop stops a running container.
docker restart stops and starts a container.
docker pause pauses a running container, “freezing” it in place.
docker unpause will unpause a running container.
docker wait blocks until running container stops.
docker kill sends a SIGKILL to a running container.
docker attach will connect to a running container.

Info

docker ps shows running containers.
- docker ps -a shows running and stopped containers.
docker logs gets logs from container. (You can use a custom log driver, but logs is only available for json-file and journald in 1.10).
docker inspect looks at all the info on a container (including IP address).
docker events gets events from container.
docker port shows public facing port of container.
docker top shows running processes in container.
docker stats shows containers’ resource usage statistics.
- docker stats --all shows a list of all containers, default shows just running.
docker diff shows changed files in the container’s FS.

Import/Export

docker cp copies files or folders between a container and the local filesystem.
docker export turns container filesystem into tarball archive stream to STDOUT.

Executing commands

docker exec to execute a command in container.

What is Docker container?

Containers are an abstraction at the app layer that packages code and dependencies together.
Multiple containers can run on the same machine and share the OS kernel with other containers, each running as isolated processes in user space.
Containers take up less space than VMs (container images are typically tens of MBs in size), can handle more applications and require fewer VMs and Operating systems.

Basic Usages

Pulling image

We can use docker pull to pull images from registry

E.g.: Pull ubuntu image

docker pull ubuntu

Running a container

Running of containers is managed with the Docker run command.

For example, we creat a container using an ubuntu:15.10 image and start it:

docker run -it ubuntu:15.10 /bin/bash

-i : interactive
-t : terminal
ubuntu:15.10: ubuntu image (version tag 15.10)
/bin/bash : command behind image

If we want our docker service to run in background, we can use argument -d. For example:

docker run -itd --name ubuntu-test-1 ubuntu /bin/bash

--name: assign a name ubuntu-test-1 to this container
-d: If we add this argument, it won’t enter the container by default

Listing containers

Listing running containers:

docker ps

Listing all containers

docker ps -a

Starting a container

docker start <stopped-container-ID>=

Ruuning a command in a running container

docker exec <container-name> <command>

For example, we run a container firstly in background

docker run -itd --name ubuntu-test-1 ubuntu /bin/bash

Check the running container:

docker ps

CONTAINER ID   IMAGE     COMMAND       CREATED          STATUS          PORTS     NAMES
67cbb5de95c2   ubuntu    "/bin/bash"   10 minutes ago   Up 10 minutes             ubuntu-test-1

Now we want to print Hello world in the terminal of container ubuntu-test-1 :

docker exec -it ubuntu-test-1 echo "Hello World"

Hello World

Stopping a container

docker stop <container-ID>

Removing a container

docker rm -f <container-ID>

Reference

docker getting-started

Last updated on Apr 5, 2022