moby: Unable to mount devices under container

Hi guys,

I’m trying to mount a device directly bind using the “devices” parameter into the container. This device is an AWS typical virtual drive. It can mount on the host without any problem.

It seems like there is no problem to run mkfs.ext3 on my mounted device, but mount -t ext3 /dev/xvdf /mnt fails with the following error:

root@eg_sshd:~# mount -t ext3 /dev/xvdf /mnt
mount: block device /dev/xvdf is write-protected, mounting read-only
mount: cannot mount block device /dev/xvdf read-only
root@eg_sshd:~# mount -t ext3 -o rw /dev/xvdf /mnt
mount: block device /dev/xvdf is write-protected, mounting read-only
mount: cannot mount block device /dev/xvdf read-only

The devices seems well recognised if I inspect the container:

    "Devices": [
        {
            "CgroupPermissions": "rwm",
            "PathInContainer": "/dev/xvdf",
            "PathOnHost": "/dev/xvdf"
        },
        {
            "CgroupPermissions": "rwm",
            "PathInContainer": "/dev/xvdg",
            "PathOnHost": "/dev/xvdg"
        }
    ],

Oh, and I’m using Ubuntu as base (just a very basic container running a sshd server - only for tests!).

Thanks for help!