Docker Image Sharing - Export Import

Upload Your Docker Image to Docker Hub on Ubuntu 24.04 - Complete Beginner's Guide

This tutorial will walk you through uploading your first Docker image to Docker Hub, making it available for anyone to download and run. We'll use the CompleteNoobs Wiki image as our example.

What is Docker Hub?

Docker Hub is like GitHub but for Docker images. It's a cloud-based registry where you can:

• Store your Docker images publicly (free) or privately (paid)
• Share containers with the community
• Download images others have created
• Automate builds from GitHub repositories

Prerequisites

• Ubuntu 24.04 with Docker installed
• A working Docker image (we'll use completenoobs/wiki:latest from the previous tutorial)
• Internet connection
• Email address for Docker Hub account

Step 1: Create Docker Hub Account

1.1: Sign Up

1. Open your web browser
2. Navigate to: https://hub.docker.com
3. Click Sign Up button (top right)
4. Fill in the registration form:
   • Docker ID: Choose a unique username (e.g., "yourname" or "completenoobs")
   • Email: Your email address
   • Password: Strong password (mix of letters, numbers, symbols)
5. Complete the CAPTCHA
6. Click Sign Up
7. Verify your email (check inbox for Docker confirmation email)

Important: Your Docker ID becomes part of your image name (e.g., yourname/wiki:latest)

1.2: Sign In to Docker Hub

1. Return to https://hub.docker.com
2. Click Sign In
3. Enter your Docker ID and password
4. You'll see your Docker Hub dashboard

Step 2: Create Repository on Docker Hub

2.1: Create New Repository

1. On Docker Hub dashboard, click Create Repository
2. Fill in repository details:
   • Name: wiki (or completenoobs-wiki)
   • Description: CompleteNoobs Wiki - MediaWiki with pre-imported content from CompleteNoobs.com
   • Visibility: Select Public (free) or Private (requires subscription)
3. Click Create

You now have a repository at: docker.io/yourdockerid/wiki

Step 3: Login to Docker Hub from Terminal

3.1: Open Terminal

# Open terminal on Ubuntu 24.04
# You can use Ctrl+Alt+T or search for "Terminal"

3.2: Login to Docker Hub

docker login

You will see:

USING WEB-BASED LOGIN

i Info → To sign in with credentials on the command line, use 'docker login -u <username>'
         

Your one-time device confirmation code is: MPMR-BKUH
Press ENTER to open your browser or submit your device code here: https://login.docker.com/activate

Waiting for authentication in the browser…

go to https://login.docker.com/activate and enter the confirmation code, after which you will be asked to sign into docker, after that your set.

the terminal will change to include:

WARNING! Your credentials are stored unencrypted in '/home/noob/.docker/config.json'.
Configure a credential helper to remove this warning. See
https://docs.docker.com/go/credential-store/

Login Succeeded

Step 4: Prepare Your Image

4.1: Check Your Local Images

docker images

You should see:

REPOSITORY            TAG       IMAGE ID       CREATED         SIZE
completenoobs/wiki    latest    abc123def456   2 hours ago     1.5GB

4.2: Tag Your Image for Docker Hub

Replace wiki with your repo name Replace yourdockerid with your actual Docker ID:

• Syntax:docker tag YOURDOCKERID/YOUR_REPO_NAME:VERSION

# Tag your image with your Docker Hub username
docker tag completenoobs/wiki:latest yourdockerid/wiki:latest

# Also create a version tag for better practice
docker tag completenoobs/wiki:latest yourdockerid/wiki:1.0

# Verify the tags
docker images

docker images | grep wiki

You should now see multiple tags for the same image ID.

Step 5: Push Image to Docker Hub

5.1: Push the Image

# Push the latest tag
docker push yourdockerid/wiki:latest

# Push the version tag
docker push yourdockerid/wiki:1.0

You'll see upload progress:

The push refers to repository [docker.io/yourdockerid/wiki]
a1b2c3d4e5f6: Pushing [==============>                     ]  45.3MB/150MB
7g8h9i0j1k2l: Pushed
3m4n5o6p7q8r: Pushing [========>                           ]  25.6MB/100MB
...
latest: digest: sha256:abc123... size: 3245

Note: First push takes longer (uploads all layers). Subsequent pushes only upload changes.

Step 6: Verify Upload

6.1: Check on Docker Hub

1. Go to: https://hub.docker.com/r/yourdockerid/wiki
2. You should see:
   • Your repository
   • Tags (latest, 1.0)
   • Last pushed timestamp
   • Image size
   • Pull count (starts at 0)

6.2: Update Repository Description

1. Click on your repository
2. Click Manage Repository (gear icon)
3. Add a detailed description
4. Add README content (supports Markdown):

 CompleteNoobs Wiki Docker Image

Pre-configured MediaWiki with CompleteNoobs.com content - For Local Use.
May require an update after first install - as for some reason some pages missing from first xml import
```bash
docker exec -it completenoobs_wiki /var/www/html/check_updates.sh
```

## Quick Start
```bash
docker run -d -p 8080:80 yourdockerid/wiki:latest
```
##Quick Start with Persistent Storage
```bash
docker run -d -p 8080:80 \
  -v completenoobs_mysql:/var/lib/mysql \
  -v completenoobs_images:/var/www/html/images \
  --name completenoobs_wiki \
  completenoobs/cnoobs-wiki:latest
```
## Features
- MediaWiki 1.44
- Pre-imported CompleteNoobs content
- YouTube extension
- PageNotice extension
- SyntaxHighlight support
- XML update system

## Default Credentials
- Username: admin
- Password: AdminPass123!

## Volumes
- `/var/lib/mysql` - Database storage
- `/var/www/html/images` - Uploaded images

## More Information
Visit: https://completenoobs.com

Step 7: Test Download (Verify It Works)

7.1: Remove Local Images (Optional)

To truly test downloading from Docker Hub:

# Stop and remove container if running
docker stop completenoobs_wiki
docker rm completenoobs_wiki

# Remove local images
docker rmi yourdockerid/wiki:latest
docker rmi yourdockerid/wiki:1.0
docker rmi completenoobs/wiki:latest

7.2: Pull From Docker Hub

# Pull your image from Docker Hub
docker pull yourdockerid/wiki:latest

# Run it
docker run -d -p 8080:80 --name test_wiki yourdockerid/wiki:latest

# Check it's working
docker logs test_wiki
curl http://localhost:8080

Step 8: Share With Others

8.1: Basic Run Command

Share this simple command for others to use your image:

docker run -d -p 8080:80 yourdockerid/wiki:latest

8.2: Docker Compose File

Create a docker-compose.yml for easier deployment:

• With version 0.1 its all in one container so these commands do not really apply - just placeholder do now - will fix for 0.2

version: '3.8'

services:
  wiki:
    image: yourdockerid/wiki:latest
    container_name: completenoobs_wiki
    ports:
      - "8080:80"
    volumes:
      - mysql_data:/var/lib/mysql
      - wiki_images:/var/www/html/images
    restart: unless-stopped
    environment:
      - TZ=America/New_York  # Adjust timezone

volumes:
  mysql_data:
  wiki_images:

Step 9: Best Practices

9.1: Versioning

Always use version tags alongside 'latest':

# Bad (only latest)
docker push yourdockerid/wiki:latest

# Good (version + latest)
docker push yourdockerid/wiki:1.0
docker push yourdockerid/wiki:latest

# When updating
docker tag yourdockerid/wiki:latest yourdockerid/wiki:1.1
docker push yourdockerid/wiki:1.1
docker push yourdockerid/wiki:latest

9.2: Image Size Optimization

Before pushing, consider reducing image size:

# Check image size
docker images yourdockerid/wiki

# Remove unnecessary files in Dockerfile
# Use multi-stage builds if possible
# Clean package manager cache

9.3: Security

• Never include passwords in image (use environment variables)
• Regularly update base images
• Scan for vulnerabilities:

# Docker Scout (built-in to Docker Desktop)
docker scout cves yourdockerid/wiki:latest

# Or use Trivy
docker run --rm -v /var/run/docker.sock:/var/run/docker.sock \
  aquasec/trivy image yourdockerid/wiki:latest

Step 10: Maintain Your Image

10.1: Update Your Image

When you need to update:

# 1. Make changes to Dockerfile or scripts
cd ~/completenoobs-docker-image

# 2. Rebuild with new version
docker build -t yourdockerid/wiki:1.1 .

# 3. Test locally
docker run -d -p 8080:80 --name test yourdockerid/wiki:1.1
# ... test everything works ...
docker stop test && docker rm test

# 4. Tag as latest
docker tag yourdockerid/wiki:1.1 yourdockerid/wiki:latest

# 5. Push both tags
docker push yourdockerid/wiki:1.1
docker push yourdockerid/wiki:latest

# 6. Update Docker Hub description with changelog

10.2: Monitor Usage

Check Docker Hub regularly for:

• Pull count (how many times downloaded)
• User issues (check if you've linked a GitHub repo)
• Security scanning results

Backup Docker Image Locally

To back up a Docker image locally as a .tar file, which can then be stored on an external drive or transferred to another server, follow these steps.

Steps

Save the Docker Image to a .tar File

Use the docker save command to export the image to a tarball:

docker save -o /path/to/backup/my-image.tar my-image:latest

• -o: Specifies the output file path (e.g., /path/to/backup/my-image.tar).
• my-image:latest: The name and tag of the image to back up.

Example:

docker save -o /home/user/backups/my-image.tar my-image:latest

Verify the Tarball

Ensure the .tar file was created:

ls -lh /path/to/backup/my-image.tar

Store on an External Drive

To store the image on an external drive (e.g., mounted at /mnt/external):

1. Copy the .tar file to the external drive:

cp /path/to/backup/my-image.tar /mnt/external/

1. Verify the file on the external drive:

ls /mnt/external/

1. Safely unmount the external drive after copying:

sudo umount /mnt/external

Send Docker Image to Another Server

To transfer the saved Docker image to another server, use tools like scp, rsync, or sftp to securely copy the .tar file.

Steps

Save the Docker Image

Follow the same docker save step as above to create the .tar file:

docker save -o /path/to/backup/my-image.tar my-image:latest

Transfer the Image to Another Server

Use scp to copy the .tar file to the remote server:

scp /path/to/backup/my-image.tar user@remote-server:/path/to/destination/

• Replace user with the remote server's username.
• Replace remote-server with the server's IP address or hostname.
• Replace /path/to/destination/ with the destination path on the remote server.

Example:

scp /home/user/backups/my-image.tar admin@192.168.1.100:/home/admin/backups/

Load the Image on the Remote Server

On the remote server, use docker load to import the .tar file into Docker:

docker load -i /path/to/destination/my-image.tar

Example:

docker load -i /home/admin/backups/my-image.tar

Verify the image is loaded:

docker images

Additional Tips

Compress the Image (Optional)

To save space, compress the .tar file before storing or transferring:

gzip /path/to/backup/my-image.tar

This creates my-image.tar.gz. To decompress on the destination:

gunzip /path/to/backup/my-image.tar.gz

Use rsync for Large Files

For large .tar files, rsync can be more reliable than scp:

rsync -avz /path/to/backup/my-image.tar user@remote-server:/path/to/destination/

Automate Backups

Create a script (e.g., backup_docker.sh) to automate backups:

#!/bin/bash
IMAGE_NAME="my-image:latest"
BACKUP_PATH="/home/user/backups"
TIMESTAMP=$(date +%F_%H-%M-%S)
docker save -o "$BACKUP_PATH/my-image-$TIMESTAMP.tar" $IMAGE_NAME

Make it executable:

chmod +x backup_docker.sh

Schedule it with cron:

crontab -e

Add a line to run daily at midnight:

0 0 * * * /path/to/backup_docker.sh

Check Disk Space

Before saving or copying, ensure there's enough disk space:

df -h /path/to/backup
df -h /mnt/external

Restoring the Image Locally

To restore the image from an external drive or a local .tar file:

docker load -i /path/to/backup/my-image.tar

Verify:

docker images

Common Issues and Solutions

Issue: "denied: requested access to the resource is denied"

Solution: You're not logged in or using wrong username

docker logout
docker login
# Make sure to use YOUR Docker ID in the tag
docker tag completenoobs/wiki:latest YOURDOCKERID/wiki:latest

Issue: "name unknown: repository name must be lowercase"

Solution: Docker Hub requires lowercase names

# Wrong
docker tag image:latest YourName/Wiki:latest

# Correct
docker tag image:latest yourname/wiki:latest

Issue: Push takes forever

Solution: Large images take time on first push

• Be patient (can take 30+ minutes for large images)
• Ensure stable internet connection
• Consider optimizing image size
• Use .dockerignore file to exclude unnecessary files

Issue: "filesystem layer verification failed"

Solution: Corrupted layer, rebuild and repush

docker build --no-cache -t yourdockerid/wiki:latest .
docker push yourdockerid/wiki:latest

Issue: Error response from daemon: Get "https://registry-1.docker.io/v2/completenoobs/cnoobs-wiki/manifests/sha256:d6cc": net/http: TLS handshake timeout

If then pulling a container docker pull completenoobs/cnoobs-wiki:0.1 you see this error:

Error response from daemon: Get "https://registry-1.docker.io/v2/completenoobs/cnoobs-wiki/manifests/sha256:d6cc65ee8f9716986c6b406a9c037b18ab3cf39326b21b42c6ad0d84c80693f4": net/http: TLS handshake timeout

• Then restart docker

sudo systemctl restart docker

Example Commands Summary

For quick reference, here are all the essential commands:

# Login to Docker Hub
docker login

# Tag your image
docker tag completenoobs/wiki:latest yourdockerid/wiki:latest
docker tag completenoobs/wiki:latest yourdockerid/wiki:1.0

# Push to Docker Hub
docker push yourdockerid/wiki:latest
docker push yourdockerid/wiki:1.0

# Others can now pull and run
docker pull yourdockerid/wiki:latest
docker run -d -p 8080:80 yourdockerid/wiki:latest

# Logout when done
docker logout