Docker Docker Networking Host and Container Network Namespaces

1. Core Command / Concept

This topic accomplishes understanding host and container network namespaces. docker network inspect.

2. Step-by-Step

1. Check the default network namespace: docker network inspect bridge
   Output: Network ID, Name, and other details.
2. Create a new network namespace: docker network create mynet
   Output: Network ID and Name.
3. Inspect the new network namespace: docker network inspect mynet
   Output: Network ID, Name, and other details.
4. ⚠️ Delete the new network namespace: docker network rm mynet
   Output: None.

3. Real Commands with Examples

1. Purpose: Create a new network namespace for a web server.
   Command: docker network create --driver bridge mywebnet
   Flags: --driver bridge specifies the network driver.
2. Purpose: Create a new network namespace for a database server.
   Command: docker network create --driver bridge mydbnet
   Flags: --driver bridge specifies the network driver.
3. Purpose: Inspect the network namespace for a running container.
   Command: docker network inspect mycontainer
   Flags: None.

4. Common Errors

1. Error: "Error response from daemon: Network not found".
   Why: The network namespace does not exist.
   Fix: docker network create mynet.
2. Error: "Error response from daemon: Network has been allocated to user".
   Why: The network namespace is already in use.
   Fix: docker network rm mynet.
3. Error: "Error response from daemon: Network is in use".
   Why: The network namespace is still in use.
   Fix: docker network rm mynet.

5. Quick Checks

1. Situation: A container is not connected to a network namespace.
   Command: docker network inspect mycontainer
   Correct Response: Network ID and Name.
2. Situation: A network namespace is not created.
   Command: docker network inspect mynet
   Correct Response: Error "Network not found".
3. Situation: A network namespace is in use.
   Command: docker network inspect mynet
   Correct Response: Error "Network is in use".

6. Last-Minute Reference

• Docker network driver: bridge, host, none.
• Docker network create flags: --driver, --subnet.
• Docker network inspect flags: None.
• Docker network rm flags: None.
• Docker network ls flags: -q, --filter.
• Docker network prune flags: -f.
• Docker network disconnect flags: None.
• Docker network connect flags: None.
• Docker network create options: --gateway, --subnet.
• Docker network inspect output: Network ID, Name, IPAM, and other details.
• Docker network rm deletes all networks.
• Docker network prune deletes all unused networks.
• Docker network disconnect disconnects a container from a network.
• Docker network connect connects a container to a network.