Docker compose DNS resolution

 

Docker Compose relies on an internal DNS server to manage and resolve service names across containers within a network.

Each container’s /etc/hosts file contains basic entries for local resolution, but inter-container communication is primarily handled through Docker’s internal DNS.

Each container is assigned a hostname that matches the service name defined in the docker-compose.yml file.

Docker’s internal DNS server keeps track of these hostnames and their corresponding container IP addresses. When a container needs to resolve another service’s name, it queries the internal DNS server.

Custom entries can be added to the /etc/hosts file of containers using the extra_hosts option in the docker-compose.yml file.
This allows you to define additional hostname-to-IP address mappings that will be included in each container's /etc/hosts file.

  • How works extra_hosts:

    • The extra_hosts option allows you to specify additional hostname-to-IP address mappings.
    • Each entry is defined in the format hostname:ip_address.
Example (docker-compose.yml file):
servicename: image: mysql environment: MYSQL_ROOT_PASSWORD: test extra_hosts: - "websrv.local:192.168.11.11"




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