Docker: how to backup and restore a swarm manager.

Docker manager nodes store the swarm state and manager logs in the /var/lib/docker/swarm/ directory, without the state you cannot restore the swarm. We don't need to take a backup from all swarm nodes since all should keep the same state.

To take a backup

sudo systemctl stop docker 
sudo tar -zvcf backup.tar.gz -C /var/lib/docker/swarm . 
sudo systemctl start docker

To restore from backup

sudo systemctl stop docker 
sudo rm -rf /var/lib/docker/swarm/* 
sudo tar -zxvf backup.tar.gz -C /var/lib/docker/swarm/ 
sudo systemctl start docker 
docker node ls