On Mon, 20 Mar 2017 08:55:21 +0100 Wouter Verhelst <w...@uter.be> wrote:
> On Mon, Mar 20, 2017 at 02:24:50AM +0100, Stefan Tauner wrote: > > Hi, > > I am writing backup scripts around nbd-client currently and ran into > > an issue. I would like to be able to determine the remote site of a > > given /dev/nbd*. I could probably hack something with pgrep > > nbd-client and the corresponding /proc/$pid/cmdlines but I would > > definitely prefer a built-in solution that won't explode now and then ;) > > Did you consider parsing the output of 'netstat' (or the symlinks under > /proc/$pid/fd) to see where the sockets point? Well, it wouldn't change anything significantly in my opinion - it is still way more work than it should be, especially since it should be rather easy within the kernel to determine and report this information back(?). > Otherwise, there's just no way to do that reliably currently. When a > device is running, nbd-client is in IO-wait state and remains there > until the device disconnects, so you can't send it any queries. Asking > the kernel would be possible, but there's no API for that. I was expecting that and thought I could try to spark a discussion within the project if that wouldn't make sense ;) Maybe some sysfs files that export other configuration and run-time data as well (whatever is available within the kernel and possibly useful for userland, e.g. transferred bytes, age of the connection). > > At any rate, you don't need to pgrep -- there's nbd-client -c which > tells you the PID of the process that holds a device, if connected. But one needs to iterate over all devices... > > > Also, it would be nice to be able to call nbd-client so that it uses > > the first free /dev/nbd* if any (similar to losetup -f file). > > This will be available with the new netlink interface that Josef wrote > recently, but it's not been merged into Linus' tree AFAICS. Cool, thanks to both of you. For my small use case I have decided to simply restrict myself to a single device for now... and rely on a fixed device path. -- Kind regards/Mit freundlichen Grüßen, Stefan Tauner ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Nbd-general mailing list Nbd-general@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/nbd-general
