docker-compose save/load images to another host

Question

I have found this, but it does not work for me.

My (really) simple docker-compose.yml:

version: '3.1'

services:

  wordpress:
    image: wordpress
    restart: always
    ports:
      - 8080:80
    environment:
      WORDPRESS_DB_PASSWORD: example

  mysql:
    image: mysql:5.7
    restart: always
    environment:
      MYSQL_ROOT_PASSWORD: example

Starting:

docker-compose up

After made some change to containers (install plugins and themes on wordpress).

docker-compose stop
docker commit main_mysql_1 test-mysql
docker commit main_wordpress_1 test-wordpress
docker save test-mysql > test-mysql.tar
docker save test-wordpress > test-wordpress.tar

Save the two tar files on another machine and load them:

docker load -i ./test-mysql.tar
docker load -i ./test-wordpress.tar

Now change the docker-compose.yml to:

version: '3.1'

services:

  wordpress:
    image: test-wordpress
    restart: always
    ports:
      - 8080:80
    environment:
      WORDPRESS_DB_PASSWORD: example

  mysql:
    image: test-mysql
    restart: always
    environment:
      MYSQL_ROOT_PASSWORD: example

But the container started is wordpress from scratch. Nothing of work done (plugin, themes, etc) was preserved.

What is my mistake? I don't want to use online repository for these private purposes.. Could you suggest a more simple and powerful procedure for pass container between two hosts?

A workaround with volumes:

version: '3.1'

services:

  wordpress:
    container_name: GREB_wordpress      
    image: wordpress
    restart: always
    ports:
      - 8080:80
    environment:
      WORDPRESS_DB_PASSWORD: example
    volumes:
      - ./www:/var/www/html  

  mysql:
    container_name: GREB_mysql
    image: mysql:5.7
    restart: always
    environment:
      MYSQL_ROOT_PASSWORD: example
    volumes:
      - ./mysql_data:/var/lib/mysql

Here is a video tutorial [How to copy a Docker image from one server to another without pushing it to a repository first?](https://www.youtube.com/watch?v=6jVGWHYs0B0) — Pathros, Oct 03 '21 at 18:39

score 9 · Answer 1 · edited Mar 08 '22 at 16:13

First of all, docker volumes are not part of an image and/or a container. So these should be saved further the docker images (docker save).

For a better understanding of docker file system, volumes, ro/rw layer, could be read http://container-solutions.com/understanding-volumes-docker/.

Figure out if our image use volumes (seek "Volumes" key):

docker inspect image_name

You have different advantage to use volumes (refer to docker documentation for well understand) such as I/O performance.

A the end, for backup volumes:

Simply backup volumes folder e.g. tar -cvzPf volume_name_backup.tar.gz /var/lib/docker/volumes/VOLUME_NAME...and restore them in the same place
Backup, restore, or migrate data volumes through another docker container
In case of db image (like my case with mysql) you can also dump the db: docker exec mysql_container /usr/bin/mysqldump -u root --password=root --all-databases > mysql_dump_backup.sql

docker-compose save/load images to another host

1 Answers1