How to list Docker mounted volumes from within the container

(EDIT - this may no longer work on Mac) If your Docker host is OS X, the mounted volumes will be type osxfs (or fuse.osxfs). You can run a

mount | grep osxfs | awk '{print $3}'

and get a list of all the mounted volumes.

If your Docker host is Linux (at least Ubuntu 14+, maybe others), the volumes appear to all be on /dev, but not on a device that is in your container's /dev filesystem. The volumes will be alongside /etc/resolv.conf, /etc/hostname, and /etc/hosts. If you do a mount | grep ^/dev to start, then filter out any of the files in ls /dev/*, then filter out the three files listed above, you should be left with host volumes.

mount | grep ^/dev/ | grep -v /etc | awk '{print $3}'

My guess is the specifics may vary from Linux to Linux. Not ideal, but at least possible to figure out.

As you can read from many of the comments you had, a container is initially nothing but a restricted, reserved part of resources that is totally cut away from the rest of your machine. It is not aware of being a Docker, and inside the container everything behaves as if it were a separate machine. Sort of like the matrix, I guess ;)

You get access to the host machine's kernel and its resources, but yet again restricted as just a filtered out set. This is done with the awesome "cgroups" functionality that comes with Unix/Linux kernels.

Now the good news: There are multiple ways for you to provide the information to your Docker, but that is something that you are going to have to provide and build yourself.

The easiest ad most powerful way is to mount the Unix socket located on your host at /var/run/docker.sock to the inside of your container at the same location. That way, when you use the Docker client inside your container you are directly talking to the docker engine on your host.

However, with great power comes great responsibility. This is a nice setup, but it is not very secure. Once someone manages to get into your docker it has root access to your host system this way.

A better way would be to provide a list of mounts through the environment settings, or clinging on to some made-up conventions to be able to predict the mounts.

(Do you realize that there is a parameter for mounting, to give mounts an alias for inside your Docker?)

Assuming you want to check what volumes are mounted from inside a linux based container you can look up entries beginning with "/dev" in /etc/mtab, removing the /etc entries

$ grep "^/dev" /etc/mtab | grep -v " \/etc/"

/dev/nvme0n1p1 /var/www/site1 ext4 rw,relatime,discard,data=ordered 0 0
/dev/nvme0n1p1 /var/www/site2 ext4 rw,relatime,discard,data=ordered 0 0