July 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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Running Dell branded Nvidia gtx 1060 in non-dell system
by Alex Volkov 03 Oct '19

03 Oct '19

Hey everyone, I'm looking to buy used Nvidia GeForce GXT 1060 to run some ML tutorials. I got a good deal on Dell OEM one. Are there any pitfalls in running one in a non-dell system? More specifically nothing even close to that i.e amd fx CPU and AMD 970 chipset. Alex. -- Sent from my Android device with K-9 Mail. Please excuse my brevity.

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Raspberry Pi 4
by Stewart Russell 04 Sep '19

04 Sep '19

More RAM, proper USB 3 and fast Ethernet, better processor, and dual HDMI output (incl 4K @ 60Hz): https://www.raspberrypi.org/products/raspberry-pi-4-model-b/

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nvme SSD: critical medium error, dev nvme0n1
by Stewart C. Russell 11 Aug '19

11 Aug '19

I'm guessing this is bad, right? [Mon Jul 29 12:59:48 2019] print_req_error: critical medium error, dev nvme0n1, sector 296089600 flags 80700 [Mon Jul 29 12:59:48 2019] print_req_error: critical medium error, dev nvme0n1, sector 296089744 flags 0 Is it an oh-shit-get-yerself-a-new-drive-NOW thing, or …? Drive is a 2+ year old Intel 512 GB SSD. Not entirely sure what the right diagnostics are for SSDs. Filesystem is showing clean but touching certain known-bad files triggers the error in the system log. Dunno if these nvme stats are useful: Smart Log for NVME device:nvme0 namespace-id:ffffffff critical_warning : 0 temperature : 25 C available_spare : 85% available_spare_threshold : 10% percentage_used : 1% data_units_read : 10,349,479 data_units_written : 10,098,299 host_read_commands : 183,018,841 host_write_commands : 136,702,227 controller_busy_time : 1,342 power_cycles : 201 power_on_hours : 15,722 unsafe_shutdowns : 10 media_errors : 803 num_err_log_entries : 844 Warning Temperature Time : 0 Critical Composite Temperature Time : 0 Thermal Management T1 Trans Count : 0 Thermal Management T2 Trans Count : 0 Thermal Management T1 Total Time : 0 Thermal Management T2 Total Time : 0 Any suggestions, please, for: * what I should be looking for in stats (nvme smart-log-add doesn't give me anything at all, so no wear-levelling stats) * a decent brand to replace it with. I'm likely okay with a SATA SSD. cheers, Stewart

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Which JSON parser in C?
by William Park 26 Jul '19

26 Jul '19

Hi all, I'm looking for JSON Parser in C. Right now, I'm eyeing JSON-GLIB, mainly because I'm sort of familiar with Glib when I was dealing with GTK+. Is there other parsers that you or others you know are actively using? And, why that and not others? I'm aware of the list on json.org. But, I'm a newbie and it would take me months to go through all that. -- William Park <opengeometry(a)yahoo.ca>

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June 2019 meeting video
by Alex Volkov 24 Jul '19

24 Jul '19

Hello everyone, The video of June talk, MyRocks 101 with Peter Sylvester, is now available here -- https://youtu.be/uJ3hctg0b-c Alex.

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Extracting data from JSON file
by William Park 24 Jul '19

24 Jul '19

How do you extract data from JSON file? For XML file, "xmlstarlet" is the tool you try first. Is there similar tool for JSON format? I tried "jq" today, but its syntax is a bit weird from first look. -- William Park <opengeometry(a)yahoo.ca>

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Request for demo on Firefox's Web Developer capabilities
by William Park 23 Jul '19

23 Jul '19

Hi all, For network tracing of something that is initiated by browser, I recently discovered Firefox's Web Developer > Network which is more immediate and convenient than Wireshark's Analyze > TCP Follow. But, I'm not a "web developer" and don't know what most other tabs mean or where to use them. So, I would like to see a quick demo or tutorial of Firefox's Web Developer capabilities, say 20 minutes max. If you can cover other browser's debugging capabilities, that would be a bonus. -- William Park <opengeometry(a)yahoo.ca>

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July 2019 meeting videos
by Alex Volkov 22 Jul '19

22 Jul '19

Hello everyone, Here are the videos from our July 2019 lightning talks as a playlist -- https://www.youtube.com/playlist?list=PLUgE6dqIXiEvuJAvXnyKu-9MOJ_BFf5vQ Here's individual lightning talk video urls: OpenStreetMap: what it is, why we care with Jarek Piórkowski -- https://youtu.be/ZZeGjh6g6nU Sleepy Head and OSCAR with Seneca Cunningham -- https://youtu.be/DgYA2RZduUo Pycon Canada 2019 announcement with Elaine Wong -- https://youtu.be/hjwbFyPudtE <https://studio.youtube.com/channel/UCM4tvQ_GLEJiJ1OKzW81Bew/videos> Taskwarrior with Tomas Babej -- https://youtu.be/gCat4d634YA Alex.

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Recommendations for useful laptop suitable for Ubuntu
by Alex Beamish 18 Jul '19

18 Jul '19

Greetings, My Windows 10 laptop died pretty close to its fifth birthday, so I'm planning on replacing it with a Linux laptop. I've used it for conference calls (hosting the Toronto Perlmongers meeings), and some light Libre Office work, so I need something better than a Bare Bones laptop, but not as wicked as a big fat gamer's rig. Refurbished is OK, and pre-loaded with Linux is also fine. Budget is perhaps $600-$800. Thanks! -- Alex Beamish Software Developer / https://ca.linkedin.com/in/alex-beamish-5111ba3 Speaker Wrangler / Toronto Perlmongers / http://to.pm.org/ Baritone, Operations Manager / Toronto Northern Lights, 2013 Champions / www.northernlightschorus.com

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