I’m setting up a Hadoop cluster using Docker containers and facing an issue with the /etc/hosts file. Here’s a detailed description of my setup and the problem:

Setup:
I’m using Docker to create multiple containers running Ubuntu 22.4.
Each container runs an instance of Hadoop (version 3.3.2).
I need to configure static IP addresses for the containers and update the /etc/hosts file accordingly to ensure proper hostname resolution within the cluster.
Problem:
After exporting and running the containers, the /etc/hosts file gets reset, removing my custom entries. Despite this, I notice that I can still start the Hadoop cluster successfully using the start-dfs.sh script, and the nodes seem to communicate correctly. However, I want to ensure that my custom /etc/hosts entries persist to avoid potential issues.

Steps Taken:

1. Created the containers and assigned static IPs:

docker run -itd --name hadoop01 --network mynet --ip 192.168.88.101 my_hadoop_image
docker run -itd --name hadoop02 --network mynet --ip 192.168.88.102 my_hadoop_image
docker run -itd --name hadoop03 --network mynet --ip 192.168.88.103 my_hadoop_image

2. Manually edited the /etc/hosts file in each container to include:

192.168.88.101 hadoop01
192.168.88.102 hadoop02
192.168.88.103 hadoop03

3. Exported and re-ran the containers:

docker export hadoop01 > hadoop01.tar
docker import hadoop01.tar new_hadoop01_image
docker run -itd --name new_hadoop01 --network mynet --ip 192.168.88.101 new_hadoop01_image

4. Observed that the /etc/hosts entries were missing, yet the Hadoop cluster still started successfully.

Questions:

• Why does the Hadoop cluster start successfully even after the
  /etc/hosts entries are reset?
• What is the best practice for persisting /etc/hosts entries in
  Docker containers to ensure reliable hostname resolution in a
  Hadoop cluster?
• Are there alternative methods or configurations within Docker or
  Hadoop that can achieve the same goal without manually editing the
  /etc/hosts file?

Additional Information:

• The Docker network is set up as a custom bridge network.
• I’m using Hadoop’s default configuration files for
  core-site.xml and hdfs-site.xml.

Any insights or suggestions to ensure persistent hostname resolution in this setup would be greatly appreciated.