docker is potentially extremely sensitive to which filesystem(s) it runs upon and also uses a potentially large amount of disk space. therefore, it would seem useful to give the uninformed user some general pointers about these facts and the informed user a place to configure them. currently by default the package installs to the standard location /var/lib/docker which is fine, however this is done under the assumption that the administrator simply wishes to use their default /var/lib block device (possibly their root device) and is aware of the sensitivity/disk space issues. i suggest adding a comment about configuring a new location. according to http://stackoverflow.com/questions/24309526/how-to-change-the-docker-image-installation-directory there are two ways to do this, either using the -g option to dockerd (currently possible via /etc/conf.d/docker) or by removing the directory and adding a symlink. according to the previous link plus https://forums.docker.com/t/how-do-i-change-the-docker-image-installation-directory/1169/8 plus my own observations, using a symlink is possibly not ideal, firstly because some users are reporting issues, secondly because people may therefore move the directory tree across filesystems in preparation for establishing a symlink and i have noticed that the contents of the directory tree do depend upon the filesystem upon it was originally created. for the latter reason, people discovering this configuration option BEFORE running dockerd for the first time is potentially going to save hassle. THEREFORE ... i recommend either... 1. adding an explicit option in the /etc/conf.d/docker file (eg. DOCKERD_GRAPH_ROOT_PATH="/var/lib/docker" # matches -g and 'man dockerd' terminology as well as existing /etc/conf.d/docker directives without being too opaque, which IMHO it would be if it were just DOCKERD_GRAPH without further comment), and having the init script translate this to -g dynamically ... OR ... 2. adding a default -g option to the existing DOCKER_OPTS="" directive in /etc/conf.d/docker. (See the other bug I just opened for another idea here)
