dig @server foobar +trace +recurse
John Miller
johnmill at brandeis.edu
Thu Jul 9 17:35:37 UTC 2015
Even after flushing Google's cache (
>> https://developers.google.com/speed/public-dns/cache), I still get the
>> same response. Does anyone have insight on +showsearch, other than the
>> following ;-)
>>
>> ...
>
> "showsearch" has nothing to do with iteration or recursion. "showsearch"
> is related to the "search list" that is used if the domain name you are
> searching for is not fully qualified (does not end in a dot). Only useful
> if /etc/resolv.conf has a "search" list (or "domain" has more than two
> labels which creates an implied search list). See man page for
> resolv.conf for more.
>
Thanks for the clarification, Bob. I definitely didn't make the connection
between "search" and "showsearch," so your response helped. Otherwise,
some careful reading and educated guessing's definitely required to figure
this out:
+[no]showsearch
Perform [do not perform] a search showing intermediate results.
This doesn't say anything about resolv.conf. "search," however, is
clear-cut: use the list in resolv.conf or don't (default):
+[no]search
Use [do not use] the search list defined by the searchlist or
domain directive in resolv.conf (if any). The
search list is not used by default.
and it's easy to see the difference:
me at mybox ~ $ grep search /etc/resolv.conf
search brandeis.edu
me at mybox ~ $ dig alumni
;; QUESTION SECTION:
;alumni. IN A
jmiller at 100degN ~ $ dig +search alumni
;; QUESTION SECTION:
;alumni.brandeis.edu. IN A
;; ANSWER SECTION:
alumni.brandeis.edu. 11396 IN A 129.64.101.157
Because it uses resolv.conf , it gives the same results as using the "host"
command.
And "showsearch" shows the full chain of queries made based on your search
path -- "+showsearch" has an implied "+search" in it:
(server fqdn: dns-rec-xs-dev1.unet.brandeis.edu; search path: brandeis.edu
unet.brandeis.edu)
[me at server ~]$ dig dns-rec-xs-dev1
;; QUESTION SECTION:
;dns-rec-xs-dev1. IN A
[me at server ~]$ dig +search dns-rec-xs-dev1
;; QUESTION SECTION:
;dns-rec-xs-dev1.unet.brandeis.edu. IN A
;; ANSWER SECTION:
dns-rec-xs-dev1.unet.brandeis.edu. 11306 IN A 129.64.100.67
[me at server ~]$ dig +showsearch dns-rec-xs-dev1
;; QUESTION SECTION:
;dns-rec-xs-dev1.brandeis.edu. IN A
;; AUTHORITY SECTION:
brandeis.edu. 1437 IN SOA dns-master.brandeis.edu.
hostmaster.brandeis.edu. 1436381401 3600 1800 1209600 1800
;; QUESTION SECTION:
;dns-rec-xs-dev1.unet.brandeis.edu. IN A
;; ANSWER SECTION:
dns-rec-xs-dev1.unet.brandeis.edu. 10655 IN A 129.64.100.67
_Two_ question and answer sections here: it shows both queries that dig
makes. Same results as running host -v; just a different format.
I'd suggest substituting:
+[no]showsearch
Perform [do not perform] a search showing intermediate results.
with
+[no]showsearch
Similar to +search, but show [do not show] results for each
domain in the searchlist. Automatically enables
+search.
I'll read through the contributors' guide and submit a patch.
John
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