Creating a service with persistence

Syntax#

• docker volume create —name <volume_name> # Creates a volume called <volume_name>
• docker run -v <volume_name>:<mount_point> -d crramirez/limesurvey:latest # Mount the <volume_name> volume in <mount_point> directory in the container

Parameters#

Remarks#

Persistence is created in docker containers using volumes. Docker have many ways to deal with volumes. Named volumes are very convenient by:

• They persist even when the container is removed using the -v option.
• The only way to delete a named volume is doing an explicit call to docker volume rm
• The named volumes can be shared among container without linking or —volumes-from option.
• They don’t have permission issues that host mounted volumes have.
• They can be manipulated using docker volume command.

Persistence with named volumes

Persistence is created in docker containers using volumes. Let’s create a Limesurvey container and persist the database, uploaded content and configuration in a named volume:

docker volume create --name mysql
docker volume create --name upload

docker run -d --name limesurvey -v mysql:/var/lib/mysql -v upload:/app/upload -p 80:80 crramirez/limesurvey:latest

Backup a named volume content

We need to create a container to mount the volume. Then archive it and download the archive to our host.

Let’s create first a data volume with some data:

docker volume create --name=data
echo "Hello World" |  docker run -i --rm=true -v data:/data ubuntu:trusty tee /data/hello.txt

Let’s backup the data:

docker run -d --name backup -v data:/data ubuntu:trusty tar -czvf /tmp/data.tgz /data
docker cp backup:/tmp/data.tgz data.tgz
docker rm -fv backup

Let’s test:

tar -xzvf data.tgz
cat data/hello.txt