Move docker containers between servers

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1

Good evening,

I have a Nextcloud App running inside Docker on a Virtual Private Server. It works, but I want to test some changes. What I want to do is to move my complete setup from VPS A to VPS B, test the changes on Server B, so they do not affect my working system and when the test was successful I can apply them on server A. What is the best way to do that? Furthermore I thought about to build a backup method from this attempt. First of all I want that the test environment works, but I am also interested in your thoughts about a backup solution based on moving containers.

What I tried first is to export my containers on server A, move them to server B and import them. I used:

docker export name > name.tar
docker import name.tar name

When I tried to run the image with:

docker run name

I got the following error:

docker: Error response from daemon: No command specified.

What I tired next is to commit and save on server A and to load on server B. I used:

docker commit name name
docker save name > name.tar

and

docker load < name.tar

When I tried to run the image with:

docker run name

I got the following error:

docker: Error response from daemon: cannot mount volume over existing file, file exists /var/lib/docker/overlay2/6c07b6c68fe0d86adf00cc385bc4022b0da5366b2db2835e1edc721a55506ed5/merged/tmp/docker.sock.

Do you have any suggestions how to solve the problem? Should the commit-save-load attempt work?

I am also wondering if I need a dockerfile on server B or is it sufficient to just load and run the images in an arbitrary order?
I used the following docker file to create the setup on server A:

# to start the service use:
# sudo docker network create proxy-tier
# sudo docker-compose up -d

# source: https://github.com/nextcloud/docker/tree/master/.examples/docker-compose/with-nginx-proxy/mariadb/apache


version: '3'

services:
  db:
    image: mariadb
    command: --transaction-isolation=READ-COMMITTED --binlog-format=ROW
    restart: always
    volumes:
      - db:/var/lib/mysql
    environment:
      - MYSQL_ROOT_PASSWORD=xxx
    env_file:
      - db.env

  app:
    image: nextcloud:apache
    restart: always
    volumes:
      - nextcloud:/var/www/html
    environment:
      - VIRTUAL_HOST=xxx
      - LETSENCRYPT_HOST=xxx
      - LETSENCRYPT_EMAIL=xxx
      - MYSQL_HOST=db
    env_file:
      - db.env
    depends_on:
      - db
    networks:
      - proxy-tier
      - default

  proxy:
    build: ./proxy
    restart: always
    ports:
      - 80:80
      - 443:443
    labels:
      com.github.jrcs.letsencrypt_nginx_proxy_companion.nginx_proxy: "true"
    volumes:
      - certs:/etc/nginx/certs:ro
      - vhost.d:/etc/nginx/vhost.d
      - html:/usr/share/nginx/html
      - /var/run/docker.sock:/tmp/docker.sock:ro
    networks:
      - proxy-tier

  letsencrypt-companion:
    image: jrcs/letsencrypt-nginx-proxy-companion
    restart: always
    volumes:
      - certs:/etc/nginx/certs
      - vhost.d:/etc/nginx/vhost.d
      - html:/usr/share/nginx/html
      - /var/run/docker.sock:/var/run/docker.sock:ro
    networks:
      - proxy-tier
    depends_on:
      - proxy

volumes:
  db:
  nextcloud:
  certs:
  vhost.d:
  html:

networks:

Operating system and version: Ubuntu 20.04.3 LTS
Docker version: 20.10.10
Nextcloud version: 21.0.0

Please let me know if I can provide further information and thank you for your help.