>-----Original Message----- >From: lxc-users [mailto:lxc-users-boun...@lists.linuxcontainers.org] On Behalf >Of Stéphane Graber >Sent: Friday, October 07, 2016 3:38 PM >To: LXC users mailing-list >Subject: Re: [lxc-users] Establish a bind mount to a running container > >On Fri, Oct 07, 2016 at 01:26:26PM +0000, Jäkel, Guido wrote: >> >-----Original Message----- >> >From: lxc-users [mailto:lxc-users-boun...@lists.linuxcontainers.org] On >> >Behalf Of Stéphane Graber >> >Sent: Friday, October 07, 2016 11:46 AM >> >To: LXC users mailing-list >> >Subject: Re: [lxc-users] Establish a bind mount to a running container >> > >> >On Fri, Oct 07, 2016 at 07:03:21AM +0000, Jäkel, Guido wrote: >> >> Dear experts, >> >> >> >> I wonder if it's possible to establish a bind mount filesystem resource >> >> from the LXC host to an already running >container in >> >an manual way, but analogous as it is done at startup time. >> >> >> >> I already figured out that the releasing an existing link is no thing; >> >> just umount it from inside the container. But is >there a >> >way to establish one while shifting the destination of a bind mount into >> >the right namespace? >> >> >> >> I ask about, because in a couple of days I have to change a (NFS) >> >> filesystem source (because of an hardware migration) >> >that is common to a large number of running containers but not frequently >> >used and I want to avoid to restart all the >> >containers with it services. >> >> >> >> thank you for advice >> >> >> >> Guido >> > >> >It's very difficult due to a number of restrictions in place in the kernel. >> > >> >The only way of doing this that I'm aware of is what we do in LXD. We >> >create a path on the host before the container starts, put that on a >> >rshared mountpoint, then bind-mount that directory into the container >> >under some arbitrary path. >> > >> >Then when you want to inject a new mount in the container, you can mount >> >it in a sub-directory of that path you create on the host, which will >> >then have the container inherit the mount entry thanks to the host >> >mountpoint being rshared and the container's mountpoint being rslave. >> > >> >Once the mountpoint shows up in the container, you can then move it to >> >whatever path you actually want it on. >> >> >> Dear Stéphane, >> >> I sorry, but I don't get it yet; some of your terms and where to do it are >> dubious to me. Maybe an example may light it up >to me: >> >> Let say, I want to inject the path >> host:/mnt/some_host_mountpoint/some_directory as a bind mount to a running >container; it should end up on container:/import/some_container_moutpoint . >On the host, the mountpoint >host:/mnt/some_host_mountpoint is mouted to a NFS source, let say >nfshost:/some_export >> >> Now please, where to issue which commands? > >You'll have to do some research yourself or hope that someone can give >you step by step instructions :) > > >A guestimate (completely untested) would be: > >Setup steps, before you first start the container: > > 1) mkdir /tmp/shared-c1 > 2) mount --bind /tmp/shared-c1 /tmp/shared-c1 > 3) mount --make-rshared /tmp/shared-c1 > 4) Add to /var/lib/lxc/c1/config => lxc.mount.entry=/tmp/shared-c1 /.shared > none bind,create=dir 0 0 > 5) lxc-start -n c1 > >At which point, you could inject a new mount with: > > 1) mkdir /tmp/share-c1/some_directory > 2) mount -- bind /mnt/some_host_mountpoint/some_directory > /tmp/share-c1/some_directory > 3) lxc-attach -n c1 -- mkdir -p /import/some_container_mountpoint > 4) lxc-attach -n c1 -- mount --move /.shared/some_directory > /import/some_container_mountpoint > > >Again, that's a very rough approximation from what I remember the LXD >code is doing (though we're doing it in a mix of Go and C).
Thanks again. I don't read through it but the first thing I read: "Steps to to before first start of the container". Does that mean, that there's no chance in my case, because all the containers are already running? Or may I (miss)use an established bind mount (or even the rootfs mount) to create the path /tmp/shared "here" at it's source path on the host , then "over-bind-mount-and-rshared" it on the host and then continue the injection? _______________________________________________ lxc-users mailing list lxc-users@lists.linuxcontainers.org http://lists.linuxcontainers.org/listinfo/lxc-users