Introduction to Docker Containers

30 July 2023 - 2 mins read time
Tags: docker docker-container

Creating a container

When we call

docker container run

It performs two tasks:

• Creating container
• Starting the container

We can create container by

docker container create

We can start container by

docker container start

When we create container from an image, we can specify its configuration. It means we can specify the evironment variables, arguments, name, etc.

Understanding the command run command:

docker container run --rm -it ubuntu:latest /bin/bash

• --rm this option tells docker to delete the container when it exits.
• -i option tells docker that the current session will be interactive and that we want to keep STDIN open.
• -t option tells docker to allocate a pseudo-TTY

Container configuration

Name

To give a container name use

docker container create --name="my-cool-container" ubuntu:latest

Labels

Lables are keyvalue pairs in Dockerfile (image).

We can specify label by using option flag -l or --label.

docker container run --rm -d --name="container-with-label" \
-l deployer=Vikas -l tester=Vikas \
ubuntu:latest

Hostname

By default the hostname is same as the container id.

We can set the hostname by

docker container run --rm --it \
--hostname="mycontainer" ubuntu:latest /bin/bash

Domain Name Server

TODO

Storage volumes

When the default disk space allocated to a container is not appropriate for the job at hand, In these cases we need storage that can persist between container deployments.

In such case we use --mount or -v option. For example,

docker container run --rm --it \
--mount=type=bind,target=/mnt/session_data,source=/data \
ubuntu:latest /bin/bash

• When you use a bind mount, a file or directory on the host machine is mounted into a container.
• The file or directory is referenced by its absolute path on the host machine.
• Neither the host mount point nor the mount point in the container needs to preexist for this command to work properly. If the host mount point does not exists, then it will be created as a directory.

You can read more about the bind mount here.