Prerequisites

• Docker data located at /var/lib/docker/volumes.
• SSH access to the target backup system.

Passwordless SSH Login

First, set up passwordless SSH login:

ssh-keygen -t rsa
ssh-copy-id root@192.168.0.225
ssh root@192.168.0.225

Docker Volume Backup Script

Create a backup script named docker_backup.sh:

#!/bin/bash
set -e

# Define variables
source_dir="/var/lib/docker/volumes"
backup_dir="/opt/docker_backups"
keep_backups=10
current_datetime=$(date +"%Y-%m-%d_%H-%M-%S")
backup_filename="$current_datetime-backup.tar"
remote_user="root"
remote_server="192.168.0.225"
remote_dir="/opt/remote_docker_backups"

# Check if source and backup directories exist
if [ ! -d "$source_dir" ]; then
  echo "Source directory does not exist."
  exit 1
fi
if [ ! -d "$backup_dir" ]; then
  echo "Backup directory does not exist."
  exit 1
fi

# Stop running Docker containers
if [ "$(docker ps -q)" ]; then
  docker stop $(docker ps -q)
fi

# Create the backup
tar -cpf "$backup_dir/$backup_filename" "$source_dir"

# Start stopped Docker containers
if [ "$(docker ps -a -q)" ]; then
  docker start $(docker ps -a -q)
fi

# Compress and transfer the backup
gzip "$backup_dir/$backup_filename"
backup_filename="$current_datetime-backup.tar.gz"
scp "$backup_dir/$backup_filename" "$remote_user@$remote_server:$remote_dir"

# Remove old backups
find "$backup_dir" -type f -name "*-backup.tar.gz" -mtime +$keep_backups -exec rm {} \;
ssh "$remote_user@$remote_server" "find $remote_dir -type f -name '*-backup.tar.gz' -mtime +$keep_backups -exec rm {} \;"

echo "Backup was created: $backup_dir/$backup_filename and copied to $remote_server:$remote_dir."

Run the script:

sudo su
chmod +x docker_backup.sh
./docker_backup.sh

Ansible Alternative

Create an Ansible playbook named docker_backup.yml:

---
- name: Docker Backup Playbook
  hosts: rpidocker
  become: yes
  vars:
    source_dir: "/var/lib/docker/volumes"
    backup_dir: "/opt/docker_backups"
    keep_backups: 10
    current_datetime: "{{ lookup('pipe', 'date +%Y-%m-%d_%H-%M-%S') }}"
    backup_filename: "{{ current_datetime }}-backup.tar"
    remote_user: "root"
    remote_server: "192.168.0.225"
    remote_dir: "/opt/remote_docker_backups"

  tasks:
    - name: Check if source directory exists
      stat:
        path: "{{ source_dir }}"
      register: source_dir_stat

    - name: Fail if source directory does not exist
      fail:
        msg: "Source directory does not exist."
      when: not source_dir_stat.stat.exists

    - name: Check if backup directory exists
      stat:
        path: "{{ backup_dir }}"
      register: backup_dir_stat

    - name: Fail if backup directory does not exist
      fail:
        msg: "Backup directory does not exist."
      when: not backup_dir_stat.stat.exists

    - name: Stop running Docker containers
      command: docker stop $(docker ps -q)
      ignore_errors: yes

    - name: Create backup archive
      command: tar -cpf "{{ backup_dir }}/{{ backup_filename }}" "{{ source_dir }}"

    - name: Start all Docker containers
      command: docker start $(docker ps -a -q)
      ignore_errors: yes

    - name: Compress the backup archive
      command: gzip "{{ backup_dir }}/{{ backup_filename }}"
      args:
        chdir: "{{ backup_dir }}"

    - name: Copy backup to remote server
      synchronize:
        src: "{{ backup_dir }}/{{ backup_filename }}.gz"
        dest: "{{ remote_user }}@{{ remote_server }}:{{ remote_dir }}"
        mode: push

    - name: Delete older backups locally
      shell: find "{{ backup_dir }}" -type f -name "*-backup.tar.gz" -mtime +{{ keep_backups }} -exec rm {} \;

    - name: Delete older backups on remote server
      shell: ssh "{{ remote_user }}@{{ remote_server }}" "find {{ remote_dir }} -type f -name '*-backup.tar.gz' -mtime +{{ keep_backups }} -exec rm {} \;"

Run the playbook:

ansible-playbook -i inventory.ini docker_backup.yml

Your inventory.ini should look like:

[rpidocker]
192.168.0.224 ansible_user=root ansible_ssh_private_key_file=/path/to/your/private/key

Conclusion

You now have two methods to back up your Docker data securely to another location within your LAN. Choose the one that best fits your needs.