A Dumb Way to Solve DockerHub Access Problems

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Sometimes inaccessible DockerHub images really become a roadblock. But for experimental needs on a personal computer, if you only want to download an image, you can solve it with a dumb method. Since restricted network scenarios do not only happen with DockerHub, I use this method quite often.

Of course, to practice this dumb method, we need a server that can access DockerHub.

The Dumb Method

Pull the required image on a machine that can access DockerHub:

docker pull mongo:latest

Confirm that the image has been pulled successfully:

docker images | grep mongo

Export it with the docker save command:

docker save mongo:latest | gzip > mongo.tar.gz

You can also export it directly without compression:

docker save -o mongo.tar mongo:latest

Move the exported image to the local machine:

scp mongo.tar.gz user@target-machine:/path/to/destination/

Import the compressed image:

gunzip -c mongo.tar.gz | docker load

For the uncompressed image:

docker load -i mongo.tar

Verify whether the image was imported successfully:

docker images | grep mongo

A Somewhat Automated Dumb Method

Batch Script

When you need to process multiple images at once, you can use a script for batch operations:

#!/bin/bash
# 需要导出的镜像列表
IMAGES=(
  "nginx:1.21"
  "mongo:5.0"
  "redis:6.2"
  "node:16-alpine"
)

# 创建存储目录
mkdir -p docker-images

# 批量导出
for img in "${IMAGES[@]}"; do
  # 替换冒号为下划线，方便文件命名
  filename=$(echo $img | tr ':' '_')
  echo "导出 $img 到 docker-images/${filename}.tar.gz"
  docker pull $img
  docker save $img | gzip > docker-images/${filename}.tar.gz
done

echo "所有镜像已导出到 docker-images/ 目录"

On the target machine, you can use a similar script to import in batch:

#!/bin/bash
# 导入目录中的所有镜像
for tarfile in docker-images/*.tar.gz; do
  echo "导入 $tarfile..."
  gunzip -c $tarfile | docker load
done

echo "所有镜像导入完成"

Split Transfer

For very large images, you can consider splitting the transfer:

Split the file on the server:

docker save huge-image:latest | gzip > huge-image.tar.gz
split -b 1G huge-image.tar.gz huge-image.part-

Reassemble and import it on the target machine:

cat huge-image.part-* > huge-image.tar.gz
gunzip -c huge-image.tar.gz | docker load

Image Signature Verification

When there are absolute security requirements.

Calculate sha256 on the source machine:

sha256sum mongo.tar.gz > mongo.tar.gz.sha256

Verify on the target machine:

sha256sum -c mongo.tar.gz.sha256

But this dumb method is usually for personal development environments, so I guess most people are probably too lazy to verify signatures.