Docker inspect for detailed info - Commands & Configuration

Introduction

Sometimes you need to see all the details about a running or stopped Docker container or image. Docker inspect shows you this detailed information in a structured way so you can understand how your container or image is configured and running.

When you want to check the IP address or network settings of a running container

When you need to see the exact command a container was started with

When you want to find the mount points or volumes used by a container

When you want to debug why a container is not working by checking its configuration

When you want to see metadata like environment variables or exposed ports of an image

Commands

This command runs an Nginx container in the background, names it 'example-nginx', and maps port 8080 on your computer to port 80 in the container.

Terminal

docker run -d --name example-nginx -p 8080:80 nginx:1.23

Expected Output

a1b2c3d4e5f67890123456789abcdef0123456789abcdef0123456789abcdef0

→

-d - Run container in detached mode (in background)

→

--name - Assign a custom name to the container

→

-p - Map host port to container port

This command shows detailed JSON information about the 'example-nginx' container, including network settings, volumes, environment variables, and more.

Terminal

docker inspect example-nginx

Expected Output

[

  {

    "Id": "a1b2c3d4e5f67890123456789abcdef0123456789abcdef0123456789abcdef0",

    "Created": "2024-06-01T12:00:00.000000000Z",

    "Path": "/docker-entrypoint.sh",

    "Args": [

      "nginx", "-g", "daemon off;"

    ],

    "State": {

      "Status": "running",

      "Running": true,

      "Paused": false,

      "Restarting": false,

      "OOMKilled": false,

      "Dead": false,

      "Pid": 12345,

      "ExitCode": 0,

      "Error": "",

      "StartedAt": "2024-06-01T12:00:01.000000000Z",

      "FinishedAt": "0001-01-01T00:00:00Z"

    },

    "Name": "/example-nginx",

    "Config": {

      "Hostname": "a1b2c3d4e5f6",

      "Env": [

        "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"

      ],

      "Cmd": [

        "nginx", "-g", "daemon off;"

      ],

      "Image": "nginx:1.23",

      "ExposedPorts": {

        "80/tcp": {}

      }

    },

    "NetworkSettings": {

      "Ports": {

        "80/tcp": [

          {

            "HostIp": "0.0.0.0",

            "HostPort": "8080"

          }

        ]

      },

      "IPAddress": "172.17.0.2"

    }

  }

]

This command extracts and shows only the IP address of the 'example-nginx' container using a Go template format.

Terminal

docker inspect --format='{{.NetworkSettings.IPAddress}}' example-nginx

Expected Output

172.17.0.2

→

--format - Format output using a Go template to show specific fields

Key Concept

Docker inspect shows all the detailed settings and status of a container or image in JSON format, helping you understand exactly how it is configured and running.

Common Mistakes

Running docker inspect without specifying a container or image name

Docker will return an error because it needs to know which container or image to inspect

Always provide the container name, container ID, or image name after docker inspect

Trying to inspect a container that is not running or does not exist

Docker will return an error or empty output because the container is not found

Check running containers with docker ps or all containers with docker ps -a before inspecting

Not using --format when you want specific info and getting overwhelmed by full JSON output

The full JSON is large and hard to read for simple info like IP address or ports

Use --format with Go templates to extract only the needed fields

Summary

Run a container with a name and port mapping to have a target for inspection.

Use docker inspect with the container name to see detailed JSON info about its configuration and state.

Use docker inspect with --format to extract specific details like IP address in a simple way.