Docker: Mounting block devices into container

Today was curious is it possible to mount block device into a docker container without mounting it on system. It’s not well documented but found one interesting comment in github.

So, if –mount option in docker run command is “magic” on top of “mount” system call, we can use it. After experimenting a bit here is an example mounting lvm volumes.

First, let’s create loop device for LVM:

dd if=/dev/zero of=/tmp/loop bs=1M count=100
losetup /dev/loop0 /tmp/loop

Then, making an LVM device:

pvcreate /dev/loop0
vgcreate vg1 /dev/loop0
lvcreate --size 90M --name lv1 vg1
mkfs.xfs /dev/vg1/lv1

And finally let’s run container and mount block device:

docker run \
  --rm -it \
  --mount='type=volume,dst=/opt,volume-driver=local,volume-opt=type=xfs,volume-opt=device=/dev/vg1/lv1' \
  ubuntu:18.04 bash

That’s it.