Libguestfs - Oct 2021 - [libguestfs/nbdkit] nbdkit server hangs during negotiation when running in background, works in foreground (Issue #16)

On Sun, Oct 24, 2021 at 01:07:19AM -0700, Nathan Shearer
wrote:
> With my current setup, the issue is reproducible. If I start the
> nbdkit server by placing a startup script in /etc/local.d to start
> on boot, it will start, but the nbd-client will always hang during
> negotiation. Killing and restarting the server and/or the client
> does not resolve the deadlock.
>
> However, if I run the exact same script manually, by logging into
> the server, then nbd-client is able to successfully connect to the
> nbdkit server and everything works as expected.
>
> During my tests, I found that when I killed nbdkit, it would see
> errors about their being insufficient "magic" or an invalid
> password. I am not using any passwords, and both the nbdkit server
> and nbd-client are on the same host, connecting through 127.0.0.1
I'm a bit unclear - how does it hang?  What happens if you enable
verbose messages (-v), what messages are sent to the log?

Also try connecting with

  LIBNBD_DEBUG=1 nbdinfo nbd://server

and see where it hangs in negotiation.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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On Sun, Oct 24, 2021 at 11:14:11AM +0100, Richard W.M. Jones
wrote:
> On Sun, Oct 24, 2021 at 01:07:19AM -0700, Nathan Shearer wrote:
> > With my current setup, the issue is reproducible. If I start the
> > nbdkit server by placing a startup script in /etc/local.d to start
> > on boot, it will start, but the nbd-client will always hang during
> > negotiation. Killing and restarting the server and/or the client
> > does not resolve the deadlock.
> >
> > However, if I run the exact same script manually, by logging into
> > the server, then nbd-client is able to successfully connect to the
> > nbdkit server and everything works as expected.
> >
> > During my tests, I found that when I killed nbdkit, it would see
> > errors about their being insufficient "magic" or an invalid
> > password. I am not using any passwords, and both the nbdkit server
> > and nbd-client are on the same host, connecting through 127.0.0.1
> 
> I'm a bit unclear - how does it hang?  What happens if you enable
> verbose messages (-v), what messages are sent to the log?
> 
> Also try connecting with
> 
>   LIBNBD_DEBUG=1 nbdinfo nbd://server
> 
> and see where it hangs in negotiation.
Also what version of nbdkit?  What's in the startup script?

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-p2v converts physical machines to virtual machines.  Boot with a
live CD or over the network (PXE) and turn machines into KVM guests.
http://libguestfs.org/virt-v2v