When working with Docker containers, forgetting to set the hostname during container creation is a common oversight. The standard approach using -h or --hostname flag only works during the initial docker run command:

# Correct initial approach (if you remembered)
docker run -h my-custom-hostname -p 8080:80 -p 2222:22 oskarhane/docker-wordpress-nginx-ss

Docker containers are designed with immutability in mind. The hostname is set during container initialization and becomes part of the container's unchangeable configuration. This architectural decision maintains container consistency but creates challenges for runtime modifications.

Method 1: Using docker exec

For temporary changes (until container restart), you can modify the hostname inside the container:

docker exec -it container_name_or_id bash -c "echo 'new-hostname' > /etc/hostname"
docker exec -it container_name_or_id bash -c "hostname new-hostname"
docker exec -it container_name_or_id bash -c "sed -i 's/127.0.1.1.*/127.0.1.1\tnew-hostname/g' /etc/hosts"

Method 2: Container Recreation

The most reliable solution is to recreate the container with proper hostname configuration:

# First, commit your running container if you have changes
docker commit container_id new_image_name

# Then create a new container with hostname
docker run -h proper-hostname -p 8080:80 -p 2222:22 --name new_container_name new_image_name

Method 3: Using docker-compose

For better hostname management, consider using docker-compose:

version: '3'
services:
  wordpress:
    image: oskarhane/docker-wordpress-nginx-ss
    hostname: my-custom-hostname
    ports:
      - "8080:80"
      - "2222:22"

• Network-dependent services may require restart after hostname change
• Some applications cache hostname at startup
• DNS resolution inside the container might need updates
• Linked containers may need hostname updates in their connection strings

For production environments, consider setting up custom DNS entries pointing to your container IPs instead of relying on container hostnames.

# Example using --dns flag
docker run --dns=your.dns.server -p 8080:80 -p 2222:22 oskarhane/docker-wordpress-nginx-ss

When working with Docker containers, you might forget to specify the hostname during the initial docker run command. Unlike other container configurations, hostnames aren't as straightforward to modify post-launch. Let's explore practical solutions.

Docker containers automatically receive a hostname matching their container ID unless explicitly set. For example:

sudo docker run -it ubuntu /bin/bash
hostname  # Shows random container ID like 'a1b2c3d4e5'

The most reliable method is to stop and recreate the container with the correct hostname:

# Get container details first
docker inspect container_name | grep -i hostname

# Stop and remove the old container
docker stop container_name
docker rm container_name

# Recreate with hostname
docker run -h mynewhost -p 8080:80 -p 2222:22 oskarhane/docker-wordpress-nginx-ss

For temporary changes (won't persist across restarts):

docker exec -it container_name /bin/bash -c "hostname newhostname && \
echo newhostname > /etc/hostname && \
sed -i 's/127.0.0.1.*/127.0.0.1 newhostname/' /etc/hosts"

For containers where you can access configuration files:

docker exec -it container_name /bin/bash
echo "my-custom-host" > /etc/hostname
echo "127.0.0.1 my-custom-host" >> /etc/hosts
exec bash

For persistent changes without recreation:

# Start temporary container with changes
docker run -it --name temp-container ubuntu /bin/bash
# Make your hostname changes inside
exit

# Commit as new image
docker commit temp-container my-new-image

# Run new image with persisted changes
docker run -it my-new-image /bin/bash

• Some applications cache hostnames - may require service restart
• Cluster environments (like Kubernetes) handle hostnames differently
• Network resolution might need additional DNS configuration