Docker Containers

Containers

1. Applications(like Microservices,WebApp,DbApp etc) are deployed on containers
2. A container is a standard unit of software that packages up code and all its dependencies so the application runs quickly and reliably from one computing environment to another.

Container Commands

Find help for all the commands related to container

docker container --help

Find help for a specified command of container ( In below example I am searching the options available for docker container ls command)

docker container ls --help

Run a Container in attached mode.

By default, Docker runs a container in the foreground.This means we can't return to our shell prompt until the process finishes.

 docker container run -it  ubuntu 

In above example docker container runs in attached mode. -it option is used to run the container is interactive terminal.

Run a Container in detached mode(-d).

This command starts the container, prints its id, and then returns to the shell prompt.

  docker container run -it -d ubuntu

Run a Container with a name (If you donot create the name of the container then docker assign some random name to the container)

We can use container name alternatively with Container id

 docker container run -it --name c1 -d ubuntu

In above example c1 is the name of the container

Run a Container with limited memory

 docker run -m 8m -dit --name web1 nginx

In above example web1 container will be created with 8mb memory allocation

Find the statistics of container web1

  docker stats web1

Run Container with limited CPU Allocation

 docker run -c 614 -dit --name db nginx
 docker run -c 410 -dit --name web nginx 

Will give 60% to the db container (614 is 60% of 1024) and 40% to the web container

Inspect a Container

docker inspect web

With above command we can inspect/debug web container

Find logs of a container

docker logs web

Above command displays the logs of web container

List running the containers

Using Docker Command

     docker ps 

Using Docker Management Command

 docker container ls

List all the containers

Using Docker Command

     docker ps -a 

Using Docker Management Command

   docker container ls --all

Intreact with Running Container

Syntax

docker exec -it <Container id/name> bash

  docker exec -it c1 bash

In above example, we are interacting with container c1 (means we are inside container c1, exit command is used to exit from container

Stop a Container

 docker stop c1

In above example container c1 will be in Exited mode

Start a Container

 docker start c1

In above example container c1 will be started.

Restart a Container

 docker restart c1

In above example container c1 will be restarted(started container will be stopped and started and Stopped container will be Started).

Pause a Container

 docker pause c1

In above example container c1 will be paused.

UnPause a Container

 docker pause c1

In above example container c1 will be unpaused.

kill a Container

 docker kill c1

In above example container c1 will be stopped forcefully-ExitCode 137.

remove a Stopped Container

 docker rm c1

In above example container c1 will be deleted.

remove a Container forcefully

 docker rm -f c1

In above example container c1 will be removed forcefully.

remove all the containers

docker rm -f $(docker ps -a -q)

Port forwarding

Run the following command to do the port forwarding with Host Machine

docker container run -it --name webserver -p 80:80 -d ubuntu

To run the application on my container and access it through web browser

docker exec -it webserver bash # Go inside the container

Run the following commands in the container

apt update # inside the container it will update the apt repo
apt install apache2 -y # it will install the apache in the container
service apache2 start # it will start apache service in container

goto your browser and use public ip address and you will be able to see Apache defualt page

exit # to exit from the container

on your local machine create a file called test.html and write some html code

Copy test.html file to webserver

docker cp test.html webserver:/var/www/html/ # copy the test.html file to the container

got to browser and PublicIP/test.html, you will be able to see the test.html output on the browser

Assignment

1. Create a container called webserver with ubuntu docker image.

2. Install apache server in the container(webserver)

3. Start apache service in the container

4. Access apache default page on the web browser

5. Create a new webpage myapp.html on the host machine and copy it to /var/www/html folder in webserver container.

6. Access myapp.html page on the browser

7. Check how much memory and cpu is consumed by web server containers.

8. Stop the container and verify that you are not able to access apache website on browser.

9. Start container and now you should be able to access the apache website.

10. Remove  webserver container