mailcow-dockerized-docs/docs/i_u_m/i_u_m_migration.en.md

!!! warning This guide assumes you intend to migrate an existing mailcow server (source) over to a brand new, empty server (target). It takes no care about preserving any existing data on your target server and will erase anything within /var/lib/docker/volumes and thus any Docker volumes you may have already set up.

!!! tip Alternatively, you can use the ./helper-scripts/backup_and_restore.sh script to create a full backup on the source machine, then install mailcow on the target machine as usual, copy over your mailcow.conf and use the same script to restore your backup to the target machine.

1. Install Docker and docker compose on your new server.

Quick installation for most operation systems:

• Docker

curl -sSL https://get.docker.com/ | CHANNEL=stable sh
# After the installation process is finished, you may need to enable the service and make sure it is started (e.g. CentOS 7)
systemctl enable docker.service

• docker compose

curl -L https://github.com/docker/compose/releases/download/v$(curl -Ls https://www.servercow.de/docker compose/latest.php)/docker compose-$(uname -s)-$(uname -m) > /usr/local/bin/docker compose
chmod +x /usr/local/bin/docker compose

Please use the latest Docker engine available and do not use the engine that ships with your distros repository.

2. Stop Docker and assure Docker has stopped:

systemctl stop docker.service
systemctl status docker.service

3. Run the following commands on the source machine (take care of adding the trailing slashes in the first path parameter as shown below!) - WARNING: This command will erase anything that may already exist under /var/lib/docker/volumes on the target machine:

rsync -aHhP --numeric-ids --delete /opt/mailcow-dockerized/ root@target-machine.example.com:/opt/mailcow-dockerized
rsync -aHhP --numeric-ids --delete /var/lib/docker/volumes/ root@target-machine.example.com:/var/lib/docker/volumes

4. Shut down mailcow and stop Docker on the source machine.

cd /opt/mailcow-dockerized
docker compose down
systemctl stop docker.service

5. Repeat step 3 with the same commands. This will be much quicker than the first time.

6. Switch over to the target machine and start Docker.

systemctl start docker.service

7. Now pull the mailcow Docker images on the target machine.

cd /opt/mailcow-dockerized
docker compose pull

8. Start the whole mailcow stack and everything should be done!

docker compose up -d

9. Finally, change your DNS settings to point to the target server.