Moving data to another location with rsync

For example, if we want to migrate docker files to new location and free some space on disk.

Stop docker daemon first

systemctl stop docker

Create or add configuration into daemon.json

# In my situation, I believe `graph` is for high version of docker.(data-root for old version)
cat >> /etc/docker/daemon.json <<EOF
{
    "graph": "/path/to/new/docker/location"
}
EOF

Copy docker files to new location

# This is equivalent to using -rlptgoD. Archive mode includes all the necessary options like copying files recursively, preserving(symbolic links, file permissions, user&group ownership and timestamps)
rsync -aP /var/lib/docker/ /path/to/new/docker/location

remove -rf /var/lib/docker

systemctl start docker

Remove old directory(free space)

rm -rf /var/lib/dokcer

Restart and check daemon

systemctl start docker

systemctl status docker

rsync command in GNU/Linux

rsync(remote synchronization) is a software utility for Unix-Like systems that efficiently sync files and directories between two hosts or machines.

There are basically two ways in which rsync can copy/sync data:

• Copying/Syncing to/from another host over any remote shell like ssh, rsh.
• Copying/Syncing through rsync daemon using TCP.

And rsync uses delta transfer algorithm, it copies only the differences between the source files present in the local-host and the existing files in the destination or the remote host.

References list:

• https://evodify.com/change-docker-storage-location/
• https://mrkandreev.name/snippets/how_to_move_docker_data_to_another_location/
• https://www.geeksforgeeks.org/rsync-command-in-linux-with-examples/