Containerizing the application

• Launch the container in detached mode
• Map host ports to container ports
• Edit appsettings.json at runtime
• Override settings using environment variables

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1. Run the Container

docker run -d \
  -p 8080:80 \
  --name corecloudapp \
  kodekloudapp:v1

docker ps

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2. Edit Configuration In-Place

1. Open a shell inside the container:
   docker exec -it corecloudapp /bin/bash
   
2. Install vim (the base image is minimal):
   apt-get update && apt-get install -y vim
   
3. Edit the settings file:
   cd /app
   vim appsettings.json
   
4. In vim, update the "Message" property:
   {
     "Logging": {
       "LogLevel": {
         "Default": "Information",
         "Microsoft.AspNetCore": "Warning"
       }
     },
     "AllowedHosts": "*",
     "Message": "Hello World from VIM !!!"
   }
   
5. Save and exit. Reload http://localhost:8080 in your browser to see the new message.

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3. Override with Environment Variables

1. Stop and remove the current container:
   docker rm -f corecloudapp
   
2. Launch a new container with the Message environment variable:
   docker run -d \
     -e Message="From Env" \
     -p 8080:80 \
     --name corecloudapp \
     kodekloudapp:v1
   
3. Refresh http://localhost:8080. The message should read From Env.

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4. Cleanup

docker rm -f corecloudapp

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Docker Command Reference

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Links and References

• Docker run reference
• Docker exec reference
• ASP.NET Core Configuration