June 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.

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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

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btrfs weirdity.
by Alvin Starr 02 Jul '20

02 Jul '20

Yesterday I had a power failure and when things came back a btrfs volume came back missing the last month few months of data. The most current date I can see on a file is Mar 29. It almost seems like the result of rolling back a snapshot but I having never used the snapshot features of btrfs it has me baffled. I guess its time to move my data to XFS. -- Alvin Starr || land: (647)478-6285 Netvel Inc. || Cell: (416)806-0133 alvin(a)netvel.net ||

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Wireless Bridge - Asus RP-N12 N300 Repeater
by William Park 25 Jun '20

25 Jun '20

FYI... For work-from-home, I got stuffs spread over two tables in my basement. Most devices don't support or have wireless capability. Problem is my router is upstair. To run an ethernet cable, it has go across hallway, living room, through kitchen, down the stair, then across basement to the opposite corner. I don't want that. So, I got - ASUS RP-N12 N300 Repeater https://www.canadacomputers.com/product_info.php?cPath=27_1056_1058&item_id… $29.88 It's repeater, access point, and media bridge. "Media Bridge" (ie. wireless bridge) is what I needed. It has one ethernet port, and that's connected to switch. So, you connect devices to the switch and it gets IP from the router. A coworker recommended - TP-LINK (TL-WA850RE) N300 300Mbps Universal WiFi Range Extender - TP-LINK (TL-WR802N) N300 Wireless N Router Nano but I went with Asus, instead. -- William Park <opengeometry(a)yahoo.ca>

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[GTALUG-Announce] Meeting on Tuesday, July 14 at 07:30 PM
by hi＠gtalug.org 24 Jun '20

24 Jun '20

# Lightning talks and Round Table This is GTALUG's version of an un-conference, a loosely structured short talks emphasizing the informal exchange of information and ideas between participants, rather than following a conventionally structured GTALUG meetings. If you already have a topic in mind please send an email <a href="mailto:speakers@gtalug.org">speakers(a)gtalug.org</a> to be added to the list of scheduled talks. A Round Table Q&A Session is where we take questions from the audience, and the audience discusses and attempts to answer those questions from their own knowledge. It's a great way to meet fellow members of our community and discover the skill sets we each bring to the table. Due to global pandemic we are going to hold this session via video conferencing. We're going to use jitsi for this meeting: Meeting room url: https://jitsi.flamy.ca/GTALUG ## Location Jitsi meeting ## Schedule * 7:30 pm - Meeting and presentation. # Code of Conduct We want a productive happy community that can welcome new ideas, improve every process every year, and foster collaboration between individuals with differing needs, interests and skills. We gain strength from diversity, and actively seek participation from those who enhance it. This code of conduct exists to ensure that diverse groups collaborate to mutual advantage and enjoyment. We will challenge prejudice that could jeopardise the participation of any person in the community. The Code of Conduct governs how we behave in public or in private whenever the Linux community will be judged by our actions. We expect it to be honoured by everyone who represents the community officially or informally, claims affiliation or participates directly. It applies to activities online or offline. We invite anybody to participate. Our community is open. Please read more about the GTALUG Code of Conduct here: https://gtalug.org/about/code-of-conduct/ If you have any questions, comments, or concerns about the GTALUG Code of Conduct please contact the GTALUG Board at board(a)gtalug.org. --- GTALUG Announce mailing list announce(a)gtalug.org https://gtalug.org/mailman/listinfo/announce

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[GTALUG-Announce] Meeting Tomorrow
by hi＠gtalug.org 16 Jun '20

16 Jun '20

<https://gtalug.org/meeting/2020-06/> # Lightning talks and Round Table with Jitsi meeting This is GTALUG's version of an un-conference, a loosely structured short talks emphasizing the informal exchange of information and ideas between participants, rather than following a conventionally structured GTALUG meetings. If you already have a topic in mind please send an email speakers(a)gtalug.org to be added to the list of scheduled talks. A Round Table Q&A Session is where we take questions from the audience, and the audience discusses and attempts to answer those questions from their own knowledge. It's a great way to meet fellow members of our community and discover the skill sets we each bring to the table. Due to global pandemic we are going to hold this session via video conferencing. We're going to use jitsi for this meeting: Meeting room url: https://jitsi.flamy.ca/GTALUG Meeting room password: aez0eireiM ## Location Jitsi meeting ## Schedule * 7:00 pm - Pre-meeting connectivity and microphone testing * 7:30 pm - Meeting and presentation. # Code of Conduct We want a productive happy community that can welcome new ideas, improve every process every year, and foster collaboration between individuals with differing needs, interests and skills. We gain strength from diversity, and actively seek participation from those who enhance it. This code of conduct exists to ensure that diverse groups collaborate to mutual advantage and enjoyment. We will challenge prejudice that could jeopardise the participation of any person in the community. The Code of Conduct governs how we behave in public or in private whenever the Linux community will be judged by our actions. We expect it to be honoured by everyone who represents the community officially or informally, claims affiliation or participates directly. It applies to activities online or offline. We invite anybody to participate. Our community is open. Please read more about the GTALUG Code of Conduct here: https://gtalug.org/about/code-of-conduct/ If you have any questions, comments, or concerns about the GTALUG Code of Conduct please contact the GTALUG Board @ board(a)gtalug.org. --- GTALUG Announce mailing list announce(a)gtalug.org https://gtalug.org/mailman/listinfo/announce

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YouTube Page
by Ansar Mohammed 16 Jun '20

16 Jun '20

I was checking out the GTALUG youtube site and was very impressed with the quality and quantity of videos on some very relevant topics. Is there a plan for more of these videos? https://www.youtube.com/channel/UCM4tvQ_GLEJiJ1OKzW81Bew

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GCC Feature Related to Warning Documentation
by Nicholas Krause 15 Jun '20

15 Jun '20

Greetings, Seems the latest version of GCC now makes warning messages be hyperlinks to the actual documentation. This does depend on your terminal but it's nice for that to exist now. Nick -- Fundamentally an organism has conscious mental states if and only if there is something that it is like to be that organism--something it is like for the organism. - Thomas Nagel

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More conferences online
by Christopher Browne 10 Jun '20

10 Jun '20

Rust has been of interest to some; there are a number of upcoming conferences, pretty well all being operated online. Some free, some definitely not. https://blog.rust-lang.org/2020/06/10/event-lineup-update.html There are fewer conferences evident for the Go language community; what's upcoming seems to be in way further flung locations... https://confs.tech/golang PyCon 2020 was back in April; I'm not sure how much of the material has been published as video streams and such... -- When confronted by a difficult problem, solve it by reducing it to the question, "How would the Lone Ranger handle this?"

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GPU Programming Questions or Figuring out the GPU Space Ideas
by Nicholas Krause 10 Jun '20

10 Jun '20

Greetings, Since GPU programming keeps coming it may be of use to try one of three things, I can help out with two of them but the other I'm unfortunately of little help. Sorry if this rather long. The ones I can help with are: 1. I've a contact in the LLVM backend/Mesa team out in Germany if I recall the location, who can answer questions depending on what they are from both the AMD side, LLVM and Mesa side. If people give me a list of questions I can try and get 2-5 answered. 2. In my notes from the LLVM talk in December I mentioned what a backend is for compilers. In general its the tuning for each CPU/GPU specific optimizations. The LLVM backends have one for AMD GPUs called AMPGPU or something similar. I can poke around it and see if there is anything in terms of interesting differences between that and the standard backends for microprocessors. From memory, GPUs use kernels in hardware and its mentioned in the ISA docs linked in etherpad what those are. Not sure about about what optimizations the back end makes around those. It may give people an idea of what is entailed in getting out something like SysCL or other GPU programming libraries,implementations and frameworks. Not to mention some of the challenges with it. The other one that may be of more help is trying to find something who works on the LLVM GPU backends or Mesa directly locally in the GTA. They would be much better at answering the current state of the GPU programming space then me. Unfortunately I'm of little help here but that's who I would try to find locally. Due to the fragmentation issues that may be the best idea, as all of the GPU programming implementations seem to be in one of or mostly focused on one of three areas: 1. Pipeline optimizations in rendering i.e. Vulcan or Metal mostly video games or other things that want stable pipelines rather than ones that are dynamic in nature for performance reasons. 2. AI a or other HPC computing seems SysCL, Cuda and maybe TensorFlow are here 3. GPU Offloading in terms of second tier specific computation Sometimes they overlap. Frankly I've not sure a) what people want and b) which are of the most use are going forward being the most implemented since last I checked. Maybe that helps people figure out the GPU space better a little as it's always seem to me to be overly complex than it really had to either due to fragmentation, or other things as Hugh pointed out, Nick -- Fundamentally an organism has conscious mental states if and only if there is something that it is like to be that organism--something it is like for the organism. - Thomas Nagel

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