Basic Commands

Running container

docker run @image

  • Let's start with simple image hello-world.
  • To run that image execute docker run hello-world.
  • Here's a output you will get
➜ docker run hello-world   
Unable to find image 'hello-world:latest' locally
latest: Pulling from library/hello-world
1b930d010525: Pull complete 
Digest: sha256:2557e3c07ed1e38f26e389462d03ed943586f744621577a99efb77324b0fe535
Status: Downloaded newer image for hello-world:latest
	
Hello from Docker!

This message shows that your installation appears to be working correctly.
...
...
  • If you look at the output you will see that docker does few things for us.
  • It will check if the image is available locally.
  • If not, it will be pulled down from the remote repository.
  • It initializes the image's name and resources containers needs like CPU, IP, Memory etc.
  • After that it will run the container.
  • When container is started, it will execute a command.
  • Command is defined in image itself. We will talk about this later.

Listing local images

docker image list

  • Or docker images
  • Lists the images that are available in your local system.
  • You can use any version of command you like.
➜ docker image list                 
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
hello-world         latest              fce289e99eb9        6 weeks ago         1.84kB

Listing container

  • When we ran the image with docker run it creates a container. Duh!! it is the definition of container.
  • How can you see list of your container?

docker container list

  • Or docker ps
  • Use any of the command above and you will see, list of running container.
➜ docker container list 
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
  • I don't see our container here, why?
  • Because hello-world is a simple image.
  • It executes one command and exits, hence container is stopped.

--all

  • If you want to see container that are stopped you can use --all option.
  • docker container list --all OR docker ps --all
➜ docker container list --all
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS                     PORTS               NAMES
bb11cd638c55        hello-world         "/hello"            9 minutes ago       Exited (0) 9 minutes ago                       stoic_shtern
  • Now we are able to see our container in the list.

Override default image command

  • After docker run @image we can pass @command and @argument it accepts.
  • Like docker run @image @command @arguments.
  • For this we will use another simple image busybox.
  • busybox has simple unix command which we can use.

docker run busybox sleep 5000

  • docker run busybox sleep 5000
  • This will run a busybox and at the end it will execute the command sleep 5000.
  • This kind of emulates a long running process, as container will not stop unless command exits.
  • If you list the container right now (in new terminal of course), you will see status is different.
  • It is not Exited.
➜ docker container list      
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
d7acdce83ad6        busybox             "sleep 5000"        23 seconds ago      Up 21 seconds                           gallant_hodgkin

Stopping running containers

docker container stop @id / @name

  • Or docker stop @id / @name
  • To stop the container you can either use name or you can use name of the container.
  • If you list the image again (don't forget --all) you will see updated status for the container.
  • If you pass space separated @id / @name to stop more than one container.

Running container in background

  • When we ran docker run busybox sleep 5000, it blocked out terminal.
  • If you don't want that to happen, we have an option to run the container in background mode.

-d option

  • If you pass -d option, when running the container it will run in background.
  • docker run @options @image @command @arguments
  • docker run -d busybox sleep 5000
  • If you run above command, it will echo container id and resume it's process in background.

Start the stopped container

docker start @name/@id

  • It will start the existing container instead of creating new one.
  • Not recommended, as container are supposed to be disposable.