Exposing a fuse mount point to another container

[akshay rao]

Hi,

I know how to expose a container's private directory to the outside world using -v, however this is not working for a fuse mount point

In my container, I have mounted a directory /mnt/test as a fuse mount point (fuse is brought up in the context of that container)

When I access that directory outside the container, it is not going through fuse... rather I just see an empty directory.

How do I make the access of that directory from the outside to also go through the fuse instance?

AR

[James Mills]

Correct me if I'm wrong but I thought bind mounted volumes

worked in the direction of host -> container?

cheers

James

James Mills / prologic

E: prol...@shortcircuit.net.au

W: prologic.shortcircuit.net.au

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[Harshavardhana]

On Thu, Jul 31, 2014 at 2:02 PM, James Mills
<prol...@shortcircuit.net.au> wrote:
> Correct me if I'm wrong but I thought bind mounted volumes
> worked in the direction of host -> container?
>

This is in-fact correct not the other way round.

--
Religious confuse piety with mere ritual, the virtuous confuse
regulation with outcomes

[fake rao]

They work both ways, I am surely able to expose a local directory to the host as well.

The only problem is, if I fuse mount on that directory, the host's IO do not go through fuse but straight to the local directory instead.

AR

On Thu, Jul 31, 2014 at 2:02 PM, James Mills <prol...@shortcircuit.net.au> wrote:

[James Mills]

On Fri, Aug 1, 2014 at 11:05 AM, fake rao <fakem...@gmail.com> wrote:

They work both ways, I am surely able to expose a local directory to the host as well.

How?

[fake rao]

I'm sorry for my wrong information... actually the containers filesystem is alway accesible locally by going to where docker rooted the container.

On the host, if I go to /var/lib/docker/btrfs/subvolumes/XXX, where XXX is the container ID obtained via docker inspect , I see the containers data.  

If the container does a fuse mount however, I do not see the fuse mounts data

I need a way where the host and therefore any other container can see this containers local directory which has been fuse mounted.

[Shannon Mann]

I am fairly confident you can't - it isn't supported (may not be able to be supported).

Docker inspect on the container tells you plenty.  To understand volumes, I'd suggest playing with the inspection of the container.

When you have a part of the disk as a Dockerfile VOLUME, you can see it in the host-side /var/lib/docker directory for that container. 
If you 'docker run' with a -v option, that will also be host-side where you specified.  Two examples I have for a foswiki container (using 'docker inspect'):
    "Volumes": {
        "/foswiki": "/opt/docker/foswiki",
        "/var/www/foswiki": "/var/lib/docker/vfs/dir/32599903467bac2a1da694ad6cf8cfd7debc132de2b519d9044292f17feb4553"
    },

client-side '/foswiki' was created with a 'docker run -v' argument with specified local and client directories.  client-side '/var/www/foswiki' was created by a Dockerfile 'VOLUME' declaration.  Note both are visible host-side.

Even --volumes-from doesn't help, as you still get the above entries in the 'inspection' of a container using --volumes-from.

When using Fuse, you are not in kernel space, so I am pretty sure the docker daemon knows nothing of the internals of said filesystem.

You MIGHT be able to do a Fuse filesystem on the host and use 'docker run -v' to expose it to the appropriate containers.  Still puts the filesystem out of root space and allows the sharing.

Thanks.

Shannon

[Shannon Mann]

A bit of digging shows:
Can't use FUSE with Docker

Apparently, a compile-time change can enable FUSE.  Don't know if that will achieve what you desire.

Thanks.

Shannon

[James Mills]

I hate to point out the obvious but the way you're "trying" to do this

seems broken, inconsistent and non-repeatable.

Could you not expose the FUSE mount point of Contienr A

over WebDAV to Container B as a normal WebDAV service

thereby ensuring reliability and repeatability?

Why hack around the internals of Docker/BTRFS (which were never designed for this)?

cheers

James

James Mills / prologic

E: prol...@shortcircuit.net.au

W: prologic.shortcircuit.net.au

On Fri, Aug 1, 2014 at 6:25 AM, akshay rao <fakem...@gmail.com> wrote:

--

[fake rao]

Yes, I can use webdav or even NFS (which I have working this way) but this ads another hop to get to what is a local share...

Thanks

AR

[James Mills]

I

On Sat, Aug 2, 2014 at 3:22 AM, fake rao <fakem...@gmail.com> wrote:

Yes, I can use webdav or even NFS (which I have working this way) but this ads another hop to get to what is a local share...

It's more repeatable than what you were trying to do hwoever

which is kind of the whole point of Docker and it's ecosystem.