Last night, I tidied up my perfunctory weekly cron job that checks on master & all slave nameserver for my two domains, making the script itself more terse and easier to read, along with eliminating some undesired junk report output. The revised Bourne script and its current output follow, below.
And, if anyone feels like helping improve it more, that'd be cool.
As you'll see, I was lazy in my design & implementation, for which I make no apology: A good-enough implementation you complete beats a better one you never quite get to, every time. And yet, it could be a lot better.
One obvious misfeature is that the script output says (figuratively) "Here's the five nameservers you ought to see; if any are missing, something is wrong", but a _better_ script would simply use shell logic to report, for each of the five, _either_ its returned zonefile S/N _or_ the fact that it doesn't respond. For extra credit, disagreement about the S/N could be somehow highlighted rather than left for the reader to vgrep.
Maybe, I dunno, state the master nameserver's S/N first, and then for each of the slaves say either "$FOO: agrees", "$FOO: no response", or "$FOO: is a rebel and says $BAR". Or, _even better_, if (as should be the case routinely) all nameservers are in agreement, say "All $N nameservers report $BAR", and cite details only in the exceptional case needing attention, where there are nonresponses or disagreements.
In general, my sense is that one wants to have much terser output when results are normal and expected: Ideally, the report's substance should be either "Everything's cool this week" or "Some things are off this week, details below."
E.g., a well-tuned logcheck report deliberately doesn't tell you anything about the many things going on that are routine, so that non-routine and possibly worrying things will stand out better.
I'm also dissatisfied with the results of parsing out "Name Server" lines from /usr/bin/whois output: Notice the auth. namserver roster is reported twice, once in all-caps, once in lower case. Why? Because "whois linuxmafia.com" (or same for unixmercenary.net) _itself_ reports the output from registrar whois server whois.1api.net twice in a row, in two stanzas, first without domain stakeholder contacts, the second time with them. I really have no idea why the latter is the case. Maybe the registrar whois servers are just unfixably funky: I know from messing around with Perl script d-check and its predecessor domain-check that the registrars mess around with whois output at unpredictable intervals. Maybe I should just be happy that the service exists, at all: A lot of Internet money people keep wanting to kill public whois, because of course it's not a profit centre (despite newer Web-mediated whois that can clot you down with ads).
And last, notice that each of the four reported "dig" output sections is prefaced by three lines of comments declaring the dig version, the command line dig is processing, then "(1 server found)", then "global options: printcmd". I kept playing last night with "+no$FOO" options, trying to eliminate those from what dig reported, and didn't find the answer. One perversity "dig" has is that it appears to answer a bit differently when run at the command line vs. in a shell script.
Of course, I could just pipe the output through a GNU sed filter that strips out lines starting with ";", but I keep feeling sheepish about not knowing the magic for tersifying "dig" output more, in scripts.
Oh, and also, my "+no$FOO" experiment gave different results from queries of the parent-zone NS records vs. queries of in-zone NS records, as to how much undesired junk output got eliminated. That's why the current script use different sets of flags for the two "dig" use-cases. I don't entirely understand why this is the case; I don't think I was hallucinating, but obviously there are complexities to taming "dig"'s output verbosity that I haven't yet mastered.
---<begin /etc/cron.weekly/mydomains contents>---
#!/bin/sh
# mydomains Cron script to sanity-check my domains' SOA records at # all of their authoritative nameservers, as a quick and # dirty way of making sure (1) they're all online and # (2) they're all serving up the same data (or at least # data with the same zonefile serial number). # # The script queries all nameservers for their current # SOA value, and then uses awk to parse out of that # verbose record just the S/N field, which is field #3. # The point is that you can visually spot offline or # aberrant nameservers by their S/Ns being (respectively) # missing or an out-of-step value. # # Written by Rick Moen (rick@linuxmafia.com) # $Id: cron.weekly,v 1.07 2023/09/08 00:23:00 rick # Copyright (C) Rick Moen, 2011-2023. Do anything you want with this work.
set -o errexit #aka "set -e": exit if any line returns non-true value set -o nounset #aka "set -u": exit upon finding an uninitialised variable
test -x /usr/bin/mail || exit 0 test -x /usr/bin/whois || exit 0 test -x /usr/bin/awk || exit 0 test -x /bin/grep || exit 0 test -x /usr/bin/dig || exit 0
{ echo "As of 2023-09-08, linuxmafia.com should show five authoritative nameservers:" echo "" echo "ns.primate.net. 198.144.194.12, (Aaron T. Porter)" echo "ns.tx.primate.net. 72.249.38.88 (Aaron T. Porter)" echo "ns3.linuxmafia.com. 107.204.234.170, aka ns.catwhisker.org (David Wolfskill)" echo "ns0.sunnyside.com. 192.147.248.10 (Al Whaley)" echo "ns1.linuxmafia.com. 96.95.217.99 (Rick Moen)" echo "" echo "As of 2023-09-08, unixmercenary.net should show five authoritative nameservers:" echo "" echo "ns.primate.net. 198.144.194.12, (Aaron T. Porter)" echo "ns.tx.primate.net. 72.249.38.88 (Aaron T. Porter)" echo "ns3.linuxmafia.com. 107.204.234.170, aka ns.catwhisker.org (David Wolfskill)" echo "ns0.sunnyside.com. 192.147.248.10 (Al Whaley)" echo "ns1.linuxmafia.com. 96.95.217.99 (Rick Moen)" echo "" echo "If any is missing from reports below, or produces odd data, something is wrong." echo "" echo "Zonefile S/Ns, linuxmafia.com:" echo "" for i in $(dig linuxmafia.com. NS +short); do dig @$i linuxmafia.com. soa +short | awk '{ print $3 " on '$i'"}'; done echo "" echo "Zonefile S/Ns, unixmercenary.net:" echo "" for i in $(dig unixmercenary.net. NS +short); do dig @$i unixmercenary.net. soa +short | awk '{ print $3 " on '$i'"}'; done echo "" echo "Authoritative nameservers from whois, linuxmafia.com:" echo "" whois linuxmafia.com | grep 'Name Server' | awk -F: '{ print $2 }' echo "" echo "Authoritative nameservers from whois, unixmercenary.net:" echo "" whois unixmercenary.net | grep 'Name Server' | awk -F: '{ print $2 }' echo "" echo "Parent-zone NS records, linuxmafia.com:" echo "" dig @$(dig com. NS +short | head -n 1) linuxmafia.com. NS +noall +auth echo "" echo "Parent-zone NS records, unixmercenary.net:" echo "" dig @$(dig net. NS +short | head -n 1) unixmercenary.net. NS +noall +auth echo "" echo "In-domain NS records, linuxmafia.com:" echo "" dig @ns1.linuxmafia.com. linuxmafia.com. ns +nocomments +noadd +nocmd +noquestion +noqr +nostats echo "" echo "In-domain NS records, unixmercenary.net:" echo "" dig @ns1.linuxmafia.com. unixmercenary.net. ns +nocomments +noadd +nocmd +noquestion +noqr +nostats
} | mail -s "Domains linuxmafia.com and unixmercenary.net SOA check" rick@linuxmafia.com
---<end>
----- Forwarded message from root root@linuxmafia.com -----
Date: Fri, 08 Sep 2023 10:27:59 -0700 From: root root@linuxmafia.com To: rick@linuxmafia.com Subject: Domains linuxmafia.com and unixmercenary.net SOA check
As of 2023-09-08, linuxmafia.com should show five authoritative nameservers:
ns.primate.net. 198.144.194.12, (Aaron T. Porter) ns.tx.primate.net. 72.249.38.88 (Aaron T. Porter) ns3.linuxmafia.com. 107.204.234.170, aka ns.catwhisker.org (David Wolfskill) ns0.sunnyside.com. 192.147.248.10 (Al Whaley) ns1.linuxmafia.com. 96.95.217.99 (Rick Moen)
As of 2023-09-08, unixmercenary.net should show five authoritative nameservers:
ns.primate.net. 198.144.194.12, (Aaron T. Porter) ns.tx.primate.net. 72.249.38.88 (Aaron T. Porter) ns3.linuxmafia.com. 107.204.234.170, aka ns.catwhisker.org (David Wolfskill) ns0.sunnyside.com. 192.147.248.10 (Al Whaley) ns1.linuxmafia.com. 96.95.217.99 (Rick Moen)
If any is missing from reports below, or produces odd data, something is wrong.
Zonefile S/Ns, linuxmafia.com:
2022041200 on ns3.linuxmafia.com. 2022041200 on ns.primate.net. 2022041200 on ns.tx.primate.net. 2022041200 on ns0.sunnyside.com. 2022041200 on ns1.linuxmafia.com.
Zonefile S/Ns, unixmercenary.net:
2022040401 on ns.primate.net. 2022040401 on ns.tx.primate.net. 2022040401 on ns3.linuxmafia.com. 2022040401 on ns0.sunnyside.com. 2022040401 on ns1.linuxmafia.com.
Authoritative nameservers from whois, linuxmafia.com:
NS.PRIMATE.NET NS.TX.PRIMATE.NET NS0.SUNNYSIDE.COM NS1.LINUXMAFIA.COM NS3.LINUXMAFIA.COM ns0.sunnyside.com ns1.linuxmafia.com 96.95.217.99 ns.primate.net ns.tx.primate.net ns3.linuxmafia.com 107.204.234.170
Authoritative nameservers from whois, unixmercenary.net:
NS.PRIMATE.NET NS.TX.PRIMATE.NET NS0.SUNNYSIDE.COM NS1.LINUXMAFIA.COM NS3.LINUXMAFIA.COM ns0.sunnyside.com ns1.linuxmafia.com 96.95.217.99 ns.primate.net ns.tx.primate.net ns3.linuxmafia.com 107.204.234.170
Parent-zone NS records, linuxmafia.com:
; <<>> DiG 9.4.2 <<>> @f.gtld-servers.net. linuxmafia.com. NS +noall +auth ; (1 server found) ;; global options: printcmd linuxmafia.com. 172800 IN NS ns0.sunnyside.com. linuxmafia.com. 172800 IN NS ns1.linuxmafia.com. linuxmafia.com. 172800 IN NS ns.primate.net. linuxmafia.com. 172800 IN NS ns.tx.primate.net. linuxmafia.com. 172800 IN NS ns3.linuxmafia.com.
Parent-zone NS records, unixmercenary.net:
; <<>> DiG 9.4.2 <<>> @k.gtld-servers.net. unixmercenary.net. NS +noall +auth ; (1 server found) ;; global options: printcmd unixmercenary.net. 172800 IN NS ns0.sunnyside.com. unixmercenary.net. 172800 IN NS ns1.linuxmafia.com. unixmercenary.net. 172800 IN NS ns.primate.net. unixmercenary.net. 172800 IN NS ns.tx.primate.net. unixmercenary.net. 172800 IN NS ns3.linuxmafia.com.
In-domain NS records, linuxmafia.com:
; <<>> DiG 9.4.2 <<>> @ns1.linuxmafia.com. linuxmafia.com. ns +nocomments +noadd +nocmd +noquestion +noqr +nostats ; (1 server found) ;; global options: printcmd linuxmafia.com. 86400 IN NS ns.primate.net. linuxmafia.com. 86400 IN NS ns0.sunnyside.com. linuxmafia.com. 86400 IN NS ns.tx.primate.net. linuxmafia.com. 86400 IN NS ns3.linuxmafia.com. linuxmafia.com. 86400 IN NS ns1.linuxmafia.com.
In-domain NS records, unixmercenary.net:
; <<>> DiG 9.4.2 <<>> @ns1.linuxmafia.com. unixmercenary.net. ns +nocomments +noadd +nocmd +noquestion +noqr +nostats ; (1 server found) ;; global options: printcmd unixmercenary.net. 86400 IN NS ns.primate.net. unixmercenary.net. 86400 IN NS ns1.linuxmafia.com. unixmercenary.net. 86400 IN NS ns0.sunnyside.com. unixmercenary.net. 86400 IN NS ns3.linuxmafia.com. unixmercenary.net. 86400 IN NS ns.tx.primate.net.
----- End forwarded message -----