Getting a Shell Inside a Container

To interact in the container, we need to get inside the container. We can consider 2 scenarios here,

Interactive Terminal on Container Startup

-it is a combination of two flag i and t. They provide an standard input output along with a terminal for a container. To get an interactive terminal for nginx server, we can run,

docker container run -it --name proxy nginx bash

We can exit using

exit

We can do detail experiments for ubuntu os,

docker container run -it --name ubuntu ubuntu

Now in the interactive terminal, first update the packages and install curl

apt-get update
apt-get install -y curl

We can use curl from the terminal.

curl google.com

We can exit from the terminal by

exit

If we again want to get the terminal in the running ubuntu machine,

docker container start ubuntu -ai

Run Program Inside Container

We can run program inside the container using the exec command.

Let's run mysql inside a container,

docker container run -d --name mysql -e MYSQL_RANDOM_ROOT_PASSWORD=true mysql

In the mysql container, there is a preinstalled program, called bash. We can execute the bash and get access to the interactive terminal.

docker container exec -it mysql bash

Let's get image of alpine from the docker-hub,

docker pull alpine

Since, the bash is not installed in the alpine and we try to run it inside the container, we will get an error, the program is not avaiable.

docker container run -it alpine bash

In alpine there is another program called sh with similar functionality. We can run sh in the alpine by,

docker container run -it alpine sh

Alpine is a minimal featured, security focused linux distribution.