Many docker volumes of driver type local - but no container

Question

I am currently learning more about docker on how to use it at development and production.

Recently I just worked through the docker docs and some other tutorial stuff on the internet and was always looking at what is happening on my machine to understand what happens.

I know have no more running or stopped containers - the output of docker ps -a is empty.

I now have a look at docker volume ls and can see many volumes with a driver type local.

I have two questions now regarding this:

1) Are those the volume containers that were used by an earlier run container and shouldn't those be removed after i removed the container? Most of the time I ran the container without a specific volume but some of those created their own volume with the -v flag.

2) How can I know that I can safeley delete such a volume if these aren't removed when I remove the container they belonged to.

Thanks for helping out.

Answer 1

not quite sure if I understand your question correctly.

1) Volumes associated with a container are only removed, if you delete the container with -v

2) To remove dangling volumes, you can use (from docker 1.9 on) docker volume rm $(docker volume ls -qf dangling=true)

Hope that helps.