On Fri, 11.11.16 14:15, Michal Sekletar (msekleta@redhat.com) wrote:
On Mon, Nov 7, 2016 at 1:20 PM, Daniel P. Berrange <berrange@redhat.com> wrote:
So if libvirt creates a private mount namespace for each QEMU and mounts a custom /dev there, this is invisible to udev, and thus udev won't/can't mess with permissions we set in our private /dev.
For hotplug, the libvirt QEMU would do the same as the libvirt LXC driver currently does. It would fork and setns() into the QEMU mount namespace and run mknod()+chmod() there, before doing the rest of its normal hotplug logic. See lxcDomainAttachDeviceMknodHelper() for what LXC does.
We try to migrate people away from using mknod and messing with /dev/ from user-space. For example, we had to deal with non-trivial problems wrt. mknod and Veritas storage stack in the past (most of these issues remain unsolved to date). I don't like to hear that you plan to get into /dev management business in libvirt too. I am judging based on past experiences, nevertheless, I don't like this plan.
Well, I'd say: if people create their own /dev, they are welcome to do in it whatever they want. They should just stay away from the host's /dev however, and not interfere with udev's own managing of that. Lennart -- Lennart Poettering, Red Hat