November 2020 - Talk - lists.gtalug.org

war story: power failure makes CentOS system unbootable
by D. Hugh Redelmeier 30 Sep '22

30 Sep '22

tl;dr / spoiler: change fstab so that /boot/efi is not automatically mounted. See the recommendation at the end of this message. My gateway computer is a little PC running CentOS. It does not come back after a power failure. The reason (as best I can tell) is interesting and I think that I have a fix. My system is UEFI. It boots from a UEFI system partition, known as /boot/efi to Linux. If this gets corrupted, it won't boot. It is a VFAT partition. On my gateway (a Zotac Zbox RI321, a cute little box with two ethernet ports), the UEFI firmware apparently won't boot if the dirty bit is set in the system partition. CentOS normally runs with /boot/efi mounted. So when the system isn't shut down cleanly, the dirty bit will be on. Consequence: the system is not going to boot after a power failure. Odd observation 1: if I put a live Fedora 25 USB stick in the system and try to boot in this otherwise-unbootable state, CentOS boots from the main disk. So this really looks like a firmware bug/quirk. Odd observation 2: fsck doesn't seem to automatically fix the system partition. Once CentOS 7 booted, I dismounted /boot/efi and did an fsck on it. $ sudo fsck /dev/sda1 fsck from util-linux 2.23.2 fsck.fat 3.0.20 (12 Jun 2013) 0x25: Dirty bit is set. Fs was not properly unmounted and some data may be corrupt. 1) Remove dirty bit 2) No action ? 1 Leaving filesystem unchanged. /dev/sda1: 16 files, 2420/51145 clusters Googling got me to <https://www.centos.org/forums/viewtopic.php?t=50917> In particular, this advice seemed quite good: ==== recommendation ==== Two other changes I recommend for UEFI systems, to each OS's /etc/fstab. - For the /boot/efi mountpoint, add the mount options x-systemd.automount,noauto - Change fs_passno (last column) to a 1 or 2; the canonical fstab instructions suggest 2, but systemd treats 1 and 2 as the same. The first change means the EFI System partition will not be automatically read-write mounted at boot time; it's a bad idea this is the default because it puts the ESP at risk especially if ther are crashes, FAT has no journal and will therefore always be marked dirty in such a case; no other UEFI OS mounts the ESP by default. Second, if anything tries to access /boot/efi (read or write), systemd will automatically mount it, and because of the fs_passno 1 or 2, it will fsck it first and that fixes and clears the dirty bit in case it's set. Right now without these changes, it's just a matter of having the right number and bad timing of crashes to render the EFI System partition corrupt.

3 9

YAD-Zenity-GTK on Pi - assistance needed
by Giles Orr 30 Jan '21

30 Jan '21

YAD ("Yet Another Dialog") is a fork of Zenity - essentially a way to display GTK+ dialogues from shell scripts. I've chosen YAD because it supports a couple things Zenity doesn't have, namely form buttons and tabs. I've created an ugly but functional interface that's meant to go on a 3.5" touch screen on a Raspberry Pi. But here's the problem: by the time it gets on a screen that small, the buttons are too small to reliably poke with a finger. So I want to increase the font size. All that was needed to fix that on my Fedora desktop was: # file: ~/.configs/gtk-3.0/settings.ini [Settings] gtk-font-name = Sans 32 And voila, 'yad' appears with a super-huge font. However - this behaviour isn't replicated on the Pi. It's an old(ish) Debian stretch install on an old Pi B (not Pi 2 B, just "Pi B"). I'm pretty sure that ~/.configs/gtk-3.0/settings.ini is the right file, because when I mis-configured it, 'yad' complained loudly. But it ignores the font setting that works fine on another host. I tried 'yad --font' which throws up what amounts to a GTK font selection dialogue, and "Sans 32" is a valid font on the Pi. Anyone got any ideas on this? -- Giles https://www.gilesorr.com/ gilesorr(a)gmail.com

4 6

dsl modem ideas for bell?
by Karen Lewellen 17 Jan '21

17 Jan '21

Hi folks, Hope you all are finding ways to feel creative. Wondering if anyone might have a suggestion providing a solution. Bell is my dsl provider, they also provide my land line and satellites service as well, but that is not the issue really. Because I still use analog phone service, its tied to some of my adaptive technology, my dsl modem / rooter combination provided by Bell is a tw or two wire model...or at least it was until this weekend. Honestly I am not a major user of data, but I do often need to connect more than one Ethernet setup, and require that someone using wireless be able to do this with little fanfare. Largely because none of bell's software works for my setup. anyway, the problem is that bell has replaced my beloved modem with one that causes my landline to click, as in makes a constant clicking noise whenever the modem is connected, which is all the time. What I am seeking is hopefully an older, but still to be found prospect, with several Ethernet ports the ability to connect wirelessly, yet being a tw model. My old one had stream in the title if that rings a..bell. I have literary had 5 technicians here since Saturday, with three of them messing up my Internet on top of not addressing the issue. Any bell modem ideas come to mind? why on earth by the way, must I only use bell equipment in the first place? Kare the ranter.

8 23

desktop thoughts on Black Friday
by D. Hugh Redelmeier 01 Dec '20

01 Dec '20

I love shopping for computers: studying what features are interesting or useful or inexpensive. I like looking for deals (recreational). I've been looking for non-notebooks (usually called desktops, even though few are on desks, and they vary in size). My current fleet is either Haswell or older, or Atom-based. My my main desktop's CPU is Haswell: Intel Core i7-4770, bought seven years ago. <https://en.wikipedia.org/wiki/Haswell_(microarchitecture)> I have not seen any really compelling reason to update these, even though I want to. Here are some features that my old computers don't have. They haven't yet compelled me to buy a new computer, even on this Black Friday. Up until now, I've replaced my main desktop every two or three years. Something shiny and new would come along. The old one would be relegated to other purposes. Here's a list of the things that make me consider getting a new desktop. Have I missed any that matter to you? ==== UltraHD ==== My old computers don't support HDMI 2.9. This makes is a barrier to using wonderful and cheap UltraHD TV sets. I use work-arounds: Haswell-era DisplayPort supports UltraHD. But not HDR (10 bits per colour per pixel) at that resolution. Dongles that convert DP to HDMI 2.0 are pretty hit-or-miss. New video cards are an obvious answer, if the computer will accept them. They are often noisy, burn power, generate heat, and are expensive. It is surprising how many new computers fail to support HDMI 2.x. Even figuring out if a particular computer supports it is often quite hard to discover from the specifications. - I was looking at a great deal on a Lenovo ThinkCentre M75q Tiny gen 2, with a very current AMD APU. But it doesn't support HDMI 2.x. <https://forums.redflagdeals.com/lenovo-canada-epp-perkopolis-796-thinkcentr…> - my XPS 15 notebook, with an UltraHD display, doesn't even support HDMI 2.x! - there has been a very good deal on a medium range notebook with the latest AMD chip. Its HDMI port doesn't support HDMI 2.x (but this isn't documented in the specs) <https://forums.redflagdeals.com/dell-dell-15-4500u-usb-c-dp-4k60-65w-pd-649…> ==== faster CPUs and more cores ==== Little of what I do is processor-bound. New processors are perhaps twice as fast (my unresearched belief). Not very compelling. My main desktop has 4 cores (8 if you count SMT). I doubt that more cores would help much of what I do. ==== NVMe SSD support ==== SATA SSD seems fast enough for my purposes. NVMe would be better, but would I notice? ==== fancy new features added to USB after USB 3.0 ==== This seems important, especially in notebooks, but I don't know what I'm missing. ==== hardware acceleration of crypto ==== AES and more is useful. I most want it on the little PCs I use as gateways for my networks (gateways are routers, firewalls, and more). ==== hardware acceleration of audio and video CODECs ==== This is most useful on streaming endpoints. But all desktops now seem to do some of that. DRM is mixed into this, often sidelining Linux desktops. We end up doing most of our TV-like streaming with a Google TV box so this takes the requirement off our desktops. ==== support for video-calling and video-conferencing ==== We just use notebooks for this. ==== power usage ==== Newer desktops could use less power but probably don't.

5 10

Network issues with github
by Alex Beamish 30 Nov '20

30 Nov '20

Hi All, This is probably a blindingly obvious question, but I'm a little stumped. I've done a little work for local business, setting up a Linux server (Ubuntu), developing some code and pushing it to github. It's all worked wonderfully until a few weeks ago, when he had someone in to do something to the network. Since then, Things Are Broken in ways that I don't understand. When I try to do anything with github, I see the response Received disconnect from 140.82.113.3 port 22:2: Connection blocked because server only allows public key authentication. Please contact your network administrator. Because I was worried I'd borked my account, this afternoon I tried again, creating a brand-new account and ssh-ing in .. and still got the same result. My github account works fine from my own machine, and also from my web provider (pair.com) so I'm guessing there's something going on within my client's network. Suggestions gratefully received. Alex -- Alex Beamish Software Developer / https://ca.linkedin.com/in/alex-beamish-5111ba3 Speaker Wrangler / Toronto Perlmongers / http://to.pm.org/ Chair, Sponsorship Committee, TPF / https://www.perlfoundation.org/ Baritone, Operations Manager / Toronto Northern Lights, 2013 Champions / www.northernlightschorus.com

3 5

Fedora 33 uses RAM for swap?
by Giles Orr 25 Nov '20

25 Nov '20

A few days after upgrading the last of my machines from Fedora 32 to 33, I noticed my main machine has acquired a new disk: NAME SIZE FSTYPE LABEL MOUNTPOINT zram0 4G [SWAP] I didn't set that up, and I don't think it was there on F32. So the OS has, without asking, co-opted 1/4 of my 16G of RAM to use as swap space. This system has an SSD, so when I initially set it up (Fedora 27), I made a conscious decision to go without swap space. I rarely push the limits of 16G. But now I'm in the situation that I have only 12G of RAM, so the system will become memory-starved earlier ... and what will it do? It will go to swap. Which is RAM anyway. How does this help? To me this seems like adding complexity without adding utility. Can someone please explain A) if I'm correct about this behaviour in the first place, and B) why it's useful? Thanks. -- Giles https://www.gilesorr.com/ gilesorr(a)gmail.com

4 4

security threats of Open Source
by D. Hugh Redelmeier 25 Nov '20

25 Nov '20

<https://www.zdnet.com/article/microsoft-spots-malicious-npm-package-stealin…> This article list six cases of malware contributed to npm (the repo for sharing node.js and JavaScript source). How many undetected cases exist? I've alway pretended that Linux distros vet their code. I'm not sure how true that is. Probably the greatest protection is the time delay between contribution and distribution. I wonder what can be done about this problem. I've said so at our meetings a few times too. Of course the problem is worse with closed source: it is impossible to audit the source. But closed source might have fewer contributors and more supervision. Of course much closed soure is built on top of open source and thuse all its weakness

7 12

Re: [GTALUG] Reverse DNS different that DNS server (reverse is a local address)
by Joseph Rocklin 23 Nov '20

23 Nov '20

Thanks for the feedback. I have a lot more learning ahead. I will try to concisely post questions, only when needed, in future. I appreciate your collective help. Sincerely, Joseph 23 Nov 2020, 10:14 am by talk(a)gtalug.org: > On Mon, 23 Nov 2020 09:20:57 -0500 (EST) > "D. Hugh Redelmeier via talk" <talk(a)gtalug.org> wrote: > >> I have no time for a careful answer. But it is important that you >> understand these points: >> > I can also spend a few minutes to add to the points below, if > that helps anyone... > >> - DNS is a distributed tree, with nodes that are authoritative for >> particular domains. >> > Yes, and not at all - names = not so much, possibly, a little like a > one or two branch tree - Numbers = always four or six "branches" > > DNS is mostly a fixed single easy thing. (although you do get weird > 'trees' like de.li.cio.us (or whatever that was) > > For names it could resemble a tree with one sometimes two or thee > branches, hardly ever more than that... (in theory it could have > millions of branches - but IRL (in real life) two or three... > > An example - would be example.com > .com says which NS server(s) is/are authorative for example > > That NS server(s) may further say where is www.example.com > > but not often do you find www.www.www.www.example.com > (although you could, in theory, have a "tree", I guess...) > > for numbers though, the delegation is only 4 "branches" deep for ipv4 > and 6 "branches" deep for ipv6 - unless you count the main .in-addr.arpa > as another two? > > So, DNS may be a bit like a very small bonsai? hehehehe > > >> - there is caching (recursive servers) if you trust them (almost >> always one does). Unless you are using DNSSec, the caching server >> can lie, sometimes usefully. >> >> - the forward domain is technically unrelated to the reverse domain. >> > yes, reverse and forward lookup is not related, but when they match, as > in for use as an email server, this is another layer in the onion of > trust. > > and, technically - it is ALL forward lookups (even a reverse lookup :) > the 'reverse' is actually you/inquirer 'reversing' the number and > adding .in-addr.arpa ) > >> The forward domain lookup uses a conventional domain name as the >> key. >> > > You can have 192.168.1.100.com - so the only 'convention' is that > forward and reverse both has 'sub domains' > > it is all really 'forward' lookups :) > > forward works from the back > 123 -> com for 123.com > > reverse works by "reversing the number" and adding .in-addr.arpa > > 192.168.1.1 -> 192 for 168 > so: 1.2.168.192.in-addr.arpa > > for example: dig NS 136.100.in-addr.arpa tells you how 136.100 is > delegated, etc etc. > >> The reverse lookup uses the IP address (in a funny format) as the >> key. >> > not so funny, just the normal ip number format > > but the reverse is from the start of the number and not the end > >> - Reverse example: to lookup the reverse for IPv4 address 1.2.3.4, >> your system actually queries 4.3.2.1.in-addr.arpa. I think you can >> see how that is constructed. >> > yes, this is all it is :) > >> - the reverse domain is a mystery to most people (because it mostly >> doesn't matter to most users). If you run a mail server, it does >> matter. >> - whoever provided you with your IP address controls the reverse >> domain for that IP address. Generally, if you pay for a static IP >> address, they will let you specify what you want them to put in the >> reverse domain for that IP address. Most ordinary consumers don't >> have static addresses and are not given a say in what the reverse >> says. >> > if whomever provided you with the number did not hijack it from > somewhere and it is in fact properly delegated, then they could, in > their own auth NS, add whatever 'name' you like to the IP number :) > >> - if your provider provides you with a CIDR of network addresses, >> static, they may delegate the reverse domain for that CIDR to a DNS >> of your choosing. This is not the normal home case. >> > > --- > Post to this mailing list talk(a)gtalug.org > Unsubscribe from this mailing list https://gtalug.org/mailman/listinfo/talk >

1 0

Reverse DNS different that DNS server (reverse is a local address)
by Joseph Rocklin 23 Nov '20

23 Nov '20

Hi all, I just tried a reverse dns lookup on whoismydns.com for my wife's computer on a family-member's network. Result: DNS Server: 67.231.208.167 Reverse DNS: pub-cdns3-wlfdle-eth1.rpub.net.rogers.com IP Owner: Rogers Does this seem correct? I have my dns settings set on my machine and I get my expected DNS results on my machine on this family member's network. Is there any reason to be concerned here? I had noticed a while back, before upgrades on this family member's network, that utopia.net was being used as the DNS server. It was on more than one machine that used that network. Now I'm wondering if somehow this network was routing, in a still-problematic way, but just via a local address? I may have confused some concepts as I am just getting my feet wet with this topic of DNS servers. If anyone has suggestions to confirm if the network is properly setup, please let me know. Thank you, Joseph Rocklin,

6 8

saving files in multiple locations
by o1bigtenor 19 Nov '20

19 Nov '20

Greetings I'm wanting to save a file (from a text editor) in multiple locations simply and easily. I've looked at 'parallel' and ran into the idea of symlink chains but so far parallel seems more for multiple in and out and symlink chains besides a reference I can't find more information. I think the rsync and cron would likely create a plethora of files which would then need cleaning so as not to waste too much space. So - - - - I dunno where to look next - - - please? TIA

2 1