Optional configuration for Linux to work better with Docker.
To create the docker group and add your user:
- Create the docker group.
sudo groupadd docker
- Add your user to the docker group.
sudo usermod -aG docker $USER
- Activate the changes to groups:
newgrp docker
- Verify that you can run docker commands without sudo.
docker images
Docker is a containerization system that packages and runs the application with its dependencies inside a container. There are several docker commands you must know when working with Docker.
To find the installed docker version Command:
docker --version
Example:
docker --version
Docker version 19.03.9, build 9d988398e7
To work with any Docker image we need to download the docker image first.
Command:
docker pull <IMAGE>
Example of pulling alpine:latest image
docker pull alpine:latest
To list all the images that are available in the host machine.
Command:
docker images
Example:
REPOSITORY TAG IMAGE ID CREATED SIZE
alpine latest c059bfaa849c 6 weeks ago 5.59MB
The docker run command is used to launch Docker containers.
When an operator executes docker run, the container process that runs is isolated in that it has its own file system, networking, and its own isolated process tree separate from the host.
Command:
docker run [options] <IMAGE>
Explore options here
Example of running alpine:latest image, the options -t allows us to access the terminal and -i gets stdin stream added. Basically using -ti adds the terminal driver.
docker run -t -i alpine:latest
or
docker run -ti alpine:latest
exit
Let us check what containers are running currently, The command. docker ps will list only running containers
Command:
docker ps
Example:
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
8973c7347905 alpine:latest "/bin/sh" 2 minutes ago Up 2 minutes ecstatic_jang
The docker exec command runs a new command in a running container. We’ll need to provide docker exec with the
name (or container ID) of the container we want to work with. We can find this information using the docker ps command:
Command to execute into container:
docker exec [OPTIONS] <CONTAINER_ID> COMMAND
Explore options here
Example: Execute into running alpine:latest container. Let us create one directory and a simple blank text file
inside the container.
docker exec -ti 8973c7347905 sh
/ # mkdir demo
/ # cd demo
/demo # touch helloworld.txt
/demo # ls
helloworld.txt
/demo #
mkdir command to create a directory or folder
cd change directory used to change the current working directory
touch command to create a blank file
Now let us stop the running container
Command:
docker stop [OPTIONS] <CONTAINER_ID>
Explore options here
Example of stopping alpine:latest running container
docker stop 8973c7347905
Here once you stop the container, the container is still available locally, but it is not in the running state.
docker ps -a will list all the containers including stopped containers.
Example output:
mis@mispl-lap-19:~$ docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
4cc4008815d8 alpine:latest "/bin/sh" 57 minutes ago Exited (137) 2 minutes ago
Let's start the stopped alpine:latest container again.
Command:
docker start [OPTIONS] <CONTAINER_ID>
Explore options here
Example of starting alpine:latest container. Before starting the container we need the container id,
so let's get the container id by docker ps -a command.
docker ps -a
docker start 4cc4008815d8
You can remove the container or multiple containers by docker rm command.
Command
docker rm [OPTIONS] <CONTAINER...>
Explore Options here Example:
docker rm 4cc4008815d8
Note: Execute this only after you stop the container
You can remove the local images by docker rmi command.
Command:
docker rmi [OPTIONS] <IMAGE_ID> / <IMAGE_ID...>
Example: Remove alpine:latest image
docker rmi c059bfaa849c