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Re: Bug - remote DNS monitoring



> On Aug 30, 2022, at 1:12 PM, Casey Deccio <casey@deccio.net> wrote:
> 
> I am having trouble tracking down a bug in my monitoring setup.  It all happened when I upgraded the monitored host (host B in my example below) to bullseye.  Note that Host A is also running bullseye, but the problem didn't show itself until Host B was upgraded.

With some help over at the bind-users mailing list [1], I discovered that nrpe-ng closes stdin when launching the command [2], and the new version of nslookup (invoked by check_dns) has issues when stdin is closed [3].

Redirecting stdin to /dev/null fixes the issue:

$ diff -u /usr/lib/python3/dist-packages/nrpe_ng/commands.py{.old,}
--- /usr/lib/python3/dist-packages/nrpe_ng/commands.py.old	2017-08-08 13:05:02.000000000 -0600
+++ /usr/lib/python3/dist-packages/nrpe_ng/commands.py	2022-09-13 17:00:36.767239885 -0600
@@ -85,6 +85,7 @@

         proc = tornado.process.Subprocess(
             run_args,
+            stdin=subprocess.DEVNULL,
             stdout=tornado.process.Subprocess.STREAM,
             close_fds=True,
             env=env)

I've filed a bug report [4].

Thanks,
Casey

[1] https://lists.isc.org/pipermail/bind-users/2022-September/106666.html
[2] https://github.com/bootc/nrpe-ng/blob/master/nrpe_ng/commands.py#L86
[3] https://github.com/libuv/libuv/blob/v1.x/src/unix/core.c#L602
[4] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1019718

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