The Docker is a popular tool for creating, deploying, and running applications using containers. One of the many useful options provided by Docker is –hostname which allows you to set specific hostname for our Docker containers. In this article, we explain the use of hostname with related examples for your reference.

Basically, the Docker is a platform that enables developers to easily create, deploy, and run applications in containers. The containers are lightweight, portable, and self-sufficient allowing for consistent environments across various stages of development and production.

Primary Terminologies Related to this Article

Before going to the actual content, we need to know Primary Terminologies to understand the article.

• Docker: The Docker is a platform that enables developers to easily create, deploy, and run applications in containers.
• Container: The Container is an isolated unit of software that packages the application and its dependencies ensuring that it runs reliably regardless of the environment.
• Hostname: A hostname is a label assigned to a device connected to a network and is used to identify the device in various forms of electronics communication such as over the internet.
• –hostname: The –hostname option in Docker is used to set the hostname of a container which can be crucial for networking and identification purposes within the containerized environment.

When to Use –hostname in Docker?

The –hostname option is particularly useful in scenarios where we need.

• Consistent Network Identification: If our application relies on a specific hostname for networking using –hostname and ensures the container is always identified correctly.
• Easier Debugging and Logging: A clear and consistent hostname can make debugging and logging more straight forward as it provides a recognizable identifier for our container.
• Inter-container Communication: When containers need to communicate with each other using hostnames, setting the hostname explicitly can simplify the configuration and interaction.

Step by Step Process to Use –hostname in Docker

• Use the docker run command with the –hostname option to create a new container. Below we provide the syntax for better understanding the concept.

Step 1: Install Docker

• Ensure that Docker is installed on your system. You can download and install Docker from Docker official website.

Step 2: Create a Docker container with –hostname

• Use the docker run command with the –hostname option to create a new container. Below we provide the syntax for you.

docker run --hostname my-container-hostname -d my-docker-image

• my-container-hostname is the desired hostname for the container.
• -d runs the container in detached mode.
• my-docker-image is the name of the Docker image you want to use.

Step 3: Verify the Hostname

• To verify that the hostname has been set correctly than you can exec into the running container and use the hostname command.

docker exec -it container_id hostname

• Replace container id with the crucial container ID obtained from the docker ps command.

Example: Setting a Hostname in Docker

Here we provide an example for better understanding the concept. For this we provide step by step guide below.

Step 1: Install Docker Desktop on Windows

• Ensure the Docker Desktop is installed on your system. If you don’t have download from Docker official website.

Step 2: Start Docker Desktop

• Open Docker Desktop and ensure it is running.

• In the above image we have two containers those are belongs to MongoDB containers.

Step 3: Run a Docker Container with a Custom Hostname

• Use the Command prompt to run a Docker container with a specific hostname. Here we use MongoDB container.

Step 4: Verify the Container is Running

• By using below Docker command list out the running docker containers.

docker ps

Step 5: Exec into the Container and Verify the Hostname

• The following is the command used for executing the bash program inside the container:

docker exec -it my_mongodb bash

Step 6: Access the MongoDB Container via localhost

• The following command helps in accessing the MongoDB container via localhost:

mongo --host localhost --port 28017

Step 7: Verify the Connection

• By verifying the connection by using below command

show dbs

Conclusion

Using –hostname option in Docker provides a way to set specific hostnames for our containers aiding in network identification, debugging and inter container communication by following the step by step guide and understanding the examples provided.

Hostname in Docker – FAQs

Why would I need to set a hostname for Docker container?

Setting a hostname can be crucial for network identification, easier debugging logging and inter container communication.

Can I change the host name of a running Docker container?

No, The hostname of a running Docker container cannot be changed. You need to set it during the creation of the container using the –hostname option.

What is the default hostname of a Docker container if –hostname is not set?

If –hostname is not set Docker assigns a default hostname based on the container ID.

Can multiple containers have the same hostname?

Yes, multiple containers can have the same hostname but this might lead to confusion and networking issues.

How does setting a hostname affect Docker compose setups?

In Docker compose you can set the hostname of services in the docker-compose.yml file using the hostname option under each service configuration.