September 2022 - Talk - lists.gtalug.org

A motivate tutorial on the Domain Name System
by D. Hugh Redelmeier 14 Sep '22

14 Sep '22

Context: Evan and Colin could not see our website in the last few days. They also may have had trouble with email from or to our lists. I don't know if this has started working again. I think that the problem is rooted in the Domain Name System. How the Domain Name System works: DNS is a distributed database that is used to "resolve" domain names (like gtalug.org, penguin.gtalug.org, www.gtalug.org) The distribution is hierarchical: - there are Name Servers designated to resolve "." (the root of the DNS tree). The IP addresses of these servers are wired into your resolver. - These servers will tell you the name servers responsible for "org" - those servers will tell you the name servers responsible for "gtalug" within "org" To improve caching, most folks use "recursive name servers", usually the one proposed by the ISP as part of the negotiation that assigns an IP address (DHCP) to your gateway. Your computer just asks this recursive name server "What's the IP address for gtalug.org?" and the recursive name server walks the DNS tree behind the scenes are returns the ultimate result. The recursive nameserver remembers results of previous queries in a cache, saving repetitive queries. Fine points of DNS: DNS serves "resource records" of different types. Some types are: A: an IPv4 address for the named domain AAAA: IPV6 address MX: the mail server NS: the Name Server DNSsec is a system where each answer from a server is authenticated by a digital signature. This is somewhat complex and many domains don't support it. How the DNS data modifications be reflected in caches: Each DNS record contains a TTL (time-to-live) in seconds. Any cache of the data must respect the TTL. So one can modify a record in the "authoritative name server" for a "zone" and be sure that only the new record will be found after the TTL of the old record. DNS can fail in may ways, some hard to diagnose. Now you know the architecture you can think about failures that you observe. Some command-line tools to figure out DNS: host(1): $ host gtalug.org gtalug.org has address 69.164.222.247 gtalug.org has IPv6 address 2600:3c03::f03c:91ff:fe50:ea0a gtalug.org mail is handled by 0 penguin.gtalug.org. dig(1): This will craft a DNS query and show you the almost-raw results. The raw results are almost overwhelming but they can be understood. $ dig gtalug.org A "A" means: ask for the A record (IPv4 address) ; <<>> DiG 9.16.31-RH <<>> gtalug.org A Leading ";" means comment. ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 30332 ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 3, ADDITIONAL: 1 This answer has three sections: the query, the actual answer to the query, the authorities: name servers that were the ultimate source of the information ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 65494 ;; QUESTION SECTION: ;gtalug.org. IN A Query: what is the A record for gtalug.org ;; ANSWER SECTION: gtalug.org. 1190 IN A 69.164.222.247 Answer: the IP address is 69.164.222.247 ;; AUTHORITY SECTION: gtalug.org. 1190 IN NS ns-128-c.gandi.net. gtalug.org. 1190 IN NS ns-165-b.gandi.net. gtalug.org. 1190 IN NS ns-136-a.gandi.net. Authorities: three distinct name servers that will serve the zone for gtalug. We (GTALUG) contract with gandi.net to supply name services. ;; Query time: 1 msec The result was quick. ;; SERVER: 127.0.0.53#53(127.0.0.53) The (recursive) name server that handled this query is on this very machine. Usint "sudo netstat -p -l" I find out that systemd-resolve is listening on this UDP port. ;; WHEN: Wed Sep 14 17:02:55 EDT 2022 ;; MSG SIZE rcvd: 133 Now, trickier: $ dig gtalug.org A +trace This will get dig to do the queries itself, asking ., then org., then gtalug.org. Ask Google's public name server: $ dig @8.8.8.8 gtalug.org A Ask CLoudflare's public name server: $ dig @1.1.1.1 gtalug.org A Note: one of Cloudflare's tricks is to give different answers to queries from different locations. This is likely true for Google too. Yesterday Google worked for gtalug.org and Cloudflare did not. Today they both work. Maybe not for everyone. Maybe the problem is solved.

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ThinkPad T60s available?
by Giles Orr 12 Sep '22

12 Sep '22

Apologies: this is not directly Linux-related. Think of it as greening the world by giving new life to old hardware ... And I know a lot of people on this list are ThinkPad users. I'm looking for a functional ThinkPad T60 (or two) preferably with a copy of Windows XP installed. XP isn't required - I think I can handle that part if needed. This is for a friend who needs to run an exceptionally old piece of music software - and for this application, real hardware makes more sense than emulation. The computer won't be connected to the Internet. Similar machines (ie. approximately that generation) would be considered, but we know the T60 works well in this context so it's preferred. -- Giles https://www.gilesorr.com/ gilesorr(a)gmail.com

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couple of unrelated electronics questions?
by Karen Lewellen 09 Sep '22

09 Sep '22

As in, not related to each other smiles First, what was the name of the still existing Toronto electronics surplus type store, now that above all electronics is gone? Need to replace the charger for an older apple iPod, and prefer doing this in person to insure it fits. And, on an unrelated note, Any ideas, even if in your closet for a pair of still-connecting-to-a soundblaster-type-soundcard computer speakers? My ideal pair would have a headphone jack too so I could listen late at night without bothering others. all my serious computer stuff is in storage. Willing to make this an amazon or comparative buy, if not from your closet, if I know what I am getting is what I seek. Thoughts oh princes of gear? Karen

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[GTALUG-Announce] Reminder: GTALUG General Meeting
by Alan Heighway 06 Sep '22

06 Sep '22

Linux and Sailboats <https://gtalug.org/meeting/2022-09/> with Colin McGregor <https://gtalug.org/> 13 September, 2022 at 07:30 PM A look at how Linux and open source software can help with sailboats, both before and after you get on the water. We're going to use Big Blue Button for this meeting: *Time:* September 13, 2022 07:30 PM Eastern Time *Join Big Blue Button:* https://blue.lpi.org/b/eva-zjc-gjy-kgl *A*lan *H*eighway <http://heighway.ca/> heighway.ca VA3WAH / VA3YKZ [image: Please consider the environment before printing] --- GTALUG Announce mailing list announce(a)gtalug.org https://gtalug.org/mailman/listinfo/announce

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tpl Linux training?
by Karen Lewellen 03 Sep '22

03 Sep '22

Hi everyone, Recall a few here have been involved with this program. May I ask what distribution of Linux was taught, and if the program returned post pandemic? Thanks, karen

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