[Nbd] How to test NBD
Hi, all, my first post here.
I'm trying to locate the source of a problem with Linux Terminal Server
Project (LTSP), which uses NBD (the new name-based protocol, not
port-based) to boot client computers.
It worked fine through Ubuntu 13.04 (Raring), but with Ubuntu 13.10
(Saucy), the clients fail to boot, displaying:
Error: socket failed: connection refused
Exiting
I have suspected that the error is NBD-related.
Regardless of the cause, I found that the bug appears between Ubuntu
kernel 3.10.0-4.13 and 3.10.0-5.14. But I am thwarted when trying to
commit bisect the Ubuntu kernel. The very first bisect attempt results
in the message "A merge base must be tested," which apparently results
from non-linear tags.
I am advised that, instead of trying further to bisect the Ubuntu
kernel, I should switch to trying to bisect the mainline kernel. The
above Ubuntu kernels map to mainline kernels 3.10.1 and 3.10.2. But it
turns out that LTSP in Ubuntu is using overlayfs or aufs, which are not
part of the mainline kernel. So I can't use LTSP to test the mainline
kernels.
I am advised that I should just test NBD, without involving LTSP or
netbooting.
But I don't know much about how to do that. I have the LTSP client
image located on the server at /opt/ltsp/images/i386.img. The LTSP NBD
configuration file sets up a reference to that with the name
"/opt/ltsp/i386." On another computer on the network running Ubuntu
standalone, I issued:
$ nbd-client <server IP> -N /opt/ltsp/i386 /dev/nbd0
This resulted in output:
Negotiation: ..sz = 1586MB
bs = 1024 sz = 1663057920 bytes
I think (but don't know) that this indicates NBD is working, at least to
some extent. In a *working Ubuntu 13.04 setup,* the above output on the
client would be followed by "* starting system logging daemon" and other
daemon startup messages.
I don't know if my two slim lines of output partly or completely
exonerate NBD as the source of my bug.
Can someone evaluate what I've done so far, and give me further or
better testing instructions if needed? Kindly keep in mind that I am
just a somewhat-experienced end-user, so don't assume too much.
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