How to analyze disk usage of a Docker container

Question

I can see that Docker takes 12GB of my filesystem:

2.7G    /var/lib/docker/vfs/dir 2.7G    /var/lib/docker/vfs 2.8G    /var/lib/docker/devicemapper/mnt 6.3G    /var/lib/docker/devicemapper/devicemapper 9.1G    /var/lib/docker/devicemapper 12G     /var/lib/docker 

But, how do I know how this is distributed over the containers?

I tried to attach to the containers by running (the new v1.3 command)

docker exec -it <container_name> bash 

and then running 'df -h' to analyze the disk usage. It seems to be working, but not with containers that use 'volumes-from'.

For example, I use a data-only container for MongoDB, called 'mongo-data'.

When I run docker run -it --volumes-from mongo-data busybox, and then df -h inside the container, It says that the filesystem mounted on /data/db (my 'mongo-data' data-only container) uses 11.3G, but when I do du -h /data/db, it says that it uses only 2.1G.

So, how do I analyze a container/volume disk usage? Or, in my case, how do I find out the 'mongo-data' container size?

Answer 1

To see the file size of your containers, you can use the --size argument of docker ps:

docker ps --size 

Answer 2

After 1.13.0, Docker includes a new command docker system df to show docker disk usage.

$ docker system df TYPE            TOTAL        ACTIVE     SIZE        RECLAIMABLE Images          5            1          2.777 GB    2.647 GB (95%) Containers      1            1          0 B         0B Local Volumes   4            1          3.207 GB    2.261 (70%) 

To show more detailed information on space usage:

$ docker system df --verbose