| 2022-06-14 21:29:27 |
Paul Collins |
description |
Running monitoring-plugins-standard 2.2-6ubuntu1.2 from Ubuntu 20.04 LTS (focal).
check_dns was failing as follows:
$ /usr/lib/nagios/plugins/check_dns -H localhost -a 127.0.0.1 -s 127.0.0.1
Connection to DNS 127.0.0.1 was refused
$ _
However, the nameserver is clearly working:
$ dig +short localhost 127.0.0.1
127.0.0.1
$ _
I straced check_dns and discovered that it was forking nslookup. Running nslookup directly reveals:
$ /usr/bin/nslookup -sil localhost 127.0.0.1
Server: 127.0.0.1
Address: 127.0.0.1#53
** server can't find localhost.openstack.lan: REFUSED
$ _
So it's not that the connection to the DNS server was refused, but the query itself was refused by the DNS server. These are very different cases, and check_dns really muddied the water here.
I fixed it by changing check_dns to query "localhost.", but better diagnostics from check_dns would have helped a lot. |
Running monitoring-plugins-standard 2.2-6ubuntu1.2 from Ubuntu 20.04 LTS (focal).
check_dns was failing as follows:
$ /usr/lib/nagios/plugins/check_dns -H localhost -a 127.0.0.1 -s 127.0.0.1
Connection to DNS 127.0.0.1 was refused
$ _
However, the nameserver is clearly working:
$ dig +short localhost 127.0.0.1
127.0.0.1
$ _
I straced check_dns and discovered that it was forking nslookup. Running nslookup directly reveals:
$ /usr/bin/nslookup -sil localhost 127.0.0.1
Server: 127.0.0.1
Address: 127.0.0.1#53
** server can't find localhost.openstack.lan: REFUSED
$ _
So it's not that the connection to the DNS server was refused, but the query itself was refused by the DNS server. These are very different cases.
A workaround is to change my nrpe check_dns command to query "localhost.". |
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