November 2019 - 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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Call for proposals for January 2020 lightning talks
by Alex Volkov 19 Nov '19

19 Nov '19

Hello Everyone, We're planning to have lightning talks at our January 14, 2020 meeting. If you would like to give a lightning talk, please email speakers(a)gtalug.org. I've put up an event page on gettogether -- https://gettogether.community/events/3158/lightning-talks/ and I will post it on the website after our December talk. Alex.

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[GTALUG-Announce] Meeting on Tuesday, December 10 at 07:30 PM
by hi＠gtalug.org 19 Nov '19

19 Nov '19

<https://gtalug.org/meeting/2019-12/> # LLVM with Nicolas Krause Nicolas will give a presentation on the basics and structure of LLVM followed by a discussion with D. Hugh Redelmeier and Q&A. ## Location George Vari Engineering and Computing Centre 245 Church Street, Room 203 Ryerson University <https://goo.gl/maps/16oJ2> <https://www.openstreetmap.org/way/23447525> ## Schedule * 6:00 pm - Please discuss on the general mailing list (i.e. <talk(a)gtalug.org>) where you want to go for dinner. * 7:30 pm - Meeting and presentation. * 9:00 pm - After each meeting, a group of GTALUGers move to The Imperial Pub (54 Dundas St East) for refreshments and more socialising. # 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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alternatives to gmail working well in Ubintu?
by Karen Lewellen 16 Nov '19

16 Nov '19

Hi folks, I was going to just ask for alternatives to consider, but want to keep the Linux element here as I mainly use a Ubuntu shell. Now that google is making it profoundly difficult reaching basic html in low graphics environments, I may need a new home. I prefer reading on the web for this account, especially as I use it largely for research needing to follow article links and work with file attachments. Any solid ideas? Thanks, Karen

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TPL is looking for a Developer
by Giles Orr 14 Nov '19

14 Nov '19

https://tpl-main.cdn.prismic.io/tpl-main/df71ffbe-1bd3-4492-9772-0e81653415… The pay may not be great, but the job has good benefits and is pretty much guaranteed 9-5 (or 10-6 or whatever you prefer within reason), no extra hours. And it's a good team of people that I'm happy to work with. Please forward this to anyone you think might be interested. Contact me off-list if you have questions. -- Giles https://www.gilesorr.com/ gilesorr(a)gmail.com

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bug in Intel processors (Skylake and later)
by D. Hugh Redelmeier 14 Nov '19

14 Nov '19

Intel has found a bug in these processors. <https://www.phoronix.com/scan.php?page=article&item=intel-jcc-microcode&num…> The bug must be commonly triggered because I've noticed no reports. Their fix is to patch the microcode in such a way as to turn off one of their accelerations for any conditional jump that ends on or crosses a 32 byte boundary. They claim that this microcode patch will slow down programs somewhere in the range 0-4%. Furthermore, Intel has released changes to GAS (GCC's assembler) that try to avoid the slowed down JCC by adding padding to the program. This too will slow down the program, but less. They have not released changes for the LLVM assembler. Nor for other things that generate x86-64 code. I wondered if the program changes would slow down AMD processors. Apparently not: <https://www.phoronix.com/scan.php?page=news_item&px=AMD-With-Intel-JCC-Asse…> It surely will have increased program size.

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[GTALUG-Announce] Meeting on Tuesday, November 12 at 07:30 PM
by hi＠gtalug.org 12 Nov '19

12 Nov '19

<https://gtalug.org/meeting/2019-11/> # taskwarrior with Tomas Babej Tomas will give a tutorial on taskwarrior -- an open-source, command-line cross platform time and task management tool ## Location George Vari Engineering and Computing Centre 245 Church Street, Room 203 Ryerson University <https://goo.gl/maps/16oJ2> <https://www.openstreetmap.org/way/23447525> ## Schedule * 6:00 pm - Please discuss on the general mailing list (i.e. <talk(a)gtalug.org>) where you want to go for dinner. * 7:30 pm - Meeting and presentation. * 9:00 pm - After each meeting, a group of GTALUGers move to The Imperial Pub (54 Dundas St East) for refreshments and more socialising. # 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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Hardcore sed foo
by Giles Orr 12 Nov '19

12 Nov '19

I've tinkered with Bash prompts for a lot of years. That's where this problem originates, but it can be considered just as a thought experiment if you prefer. We have the directory we're in, for example: /Users/gorr/.bashprompt/really/deep/directory/structure/even/deeper (I keep my prompts in ~/.bashprompt/ , and a very long directory name is often a cause of breakage, so I keep one around to break them ...) I want to shorten the directory name to just the first letters: export newPWD=$(echo ${PWD} | sed -e "s@${HOME}@~@" -e 's@ $/.$[^/]*@\1@g') echo $newPWD ~/./r/d/d/s/e/d This does '~' replacement for $HOME and then substitutes the first letter of each directory for the full directory name. Here's the question: if the first letter of the directory name is a dot '.', can sed then capture one character more so that the output would become: ~/.b/r/d/d/s/e/d I think this would be pretty easy with Bash and a loop, but that's a lot of processing so I'd rather not go down that road. I suspect sed is capable of this, but I haven't delved deeply enough into the tool to even know where to start. This may in fact be a regex problem more than a sed problem - either way I'm kind of stumped. I'm open to simpler implementations using other (standard system) tools as well. -- Giles https://www.gilesorr.com/ gilesorr(a)gmail.com

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TekSavvy or Rogers blocking apt user agent
by Jamon Camisso 07 Nov '19

07 Nov '19

Well this is a new low: https://askubuntu.com/questions/1185612/apt-get-stuck-on-waiting-for-header… Mind-boggling that it is/was even an issue at an ISP & HTTP level. Either they have a giant whitelist of browser agents to maintain, or a blacklist to update and added apt to it. In either case, they're looking at HTTP traffic and acting on it directly. Still an issue for anyone? Jamon

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Semiaccurate: misleading Intel messaging
by D. Hugh Redelmeier 06 Nov '19

06 Nov '19

Semiaccurate is a site that mostly discusses technical details of new chips. Very insightful and opinionated. And sometimes wrong (hence the name). Yesterday they published scathing article on Intel's messaging. I thought it was well-worth reading. Note: they want you to subscribe (not cheap) so most articles have a free part and a subscribers-only part. This one seems to be all free. <https://semiaccurate.com/2019/11/05/intel-messaging-hits-a-new-low/> A similar site which I follow is <https://www.linleygroup.com/> They publish the venerable Microprocessor Report. What sites do you find valuable for chip news?

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