September 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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some USB sticks are slow!
by D. Hugh Redelmeier 02 Oct '19

02 Oct '19

I bought some inexpensive SanDisk Cruzer Glide 16GB USB sticks from Walmart last year. Cheap. Today I copied the CentOS 8 installation image onto one. time sudo dd if=CentOS-8-x86_64-1905-dvd1.iso of=/dev/sdg oflag=direct bs=16M (I used a USB 3 port on my dessktop.) It seemed to take a long time, so I did this to see if anything was happening (the dd process' PID was 29047): sudo kill -s USER1 29047 Yes, there was progress, but not as much as I would expect. The final statistics were: 425+1 records in 425+1 records out 7135559680 bytes (7.1 GB, 6.6 GiB) copied, 1560.63 s, 4.6 MB/s real 26m4.152s user 0m0.072s sys 0m4.706s This amounts to about 4.56 MB/s. That's even less than the poor Average Sustained Write Speed 7.64 MB/s reported here: <https://usb.userbenchmark.com/SpeedTest/2718/SanDisk-Cruzer-Glide> Note: this stick hasn't been written to often. It should not be near the end of its life (that could slow down a flash device).

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IPv6 only WiFi hotspot
by Val Kulkov 28 Sep '19

28 Sep '19

I found myself connected to an IPv6-only WiFi hotspot a couple of weeks ago. In a small town in Greece. At first, I could not understand why I was getting DNS errors for so many sites. Then it occurred to me to check my connection with ifconfig, and voila: I had an IPv6 address, but no IPv4. In short: - Google, Wikipedia, Facebook worked fine - Expedia, Travelocity, Hotels.com, Flighthub, TripAdvisor, Travelzoo were not accessible - many sites found through Google were not accessible I am guessing that some Internet providers in Greece probably charge less for a service that does not involve allocating an IPv4 address for a downstream link. Still, considering that setting up an IPv6-to-IPv4 tunnel is relatively easy, I do not understand what stops these providers from setting up such a tunnel and using it for all of their downstream links who would be assigned an IPv4 address from a private address space. I also fail to understand why major travel sites such as Expedia are not yet IPv6-enabled. This makes no sense to me, especially considering that travelers are more likely than other categories of people to find themselves in an unusual hotspot with no access to public IPv4 address space.

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Re: [GTALUG] Was: Linux kernel 5.3 - Now: SPF and Anti Forgery
by Stewart C. Russell 23 Sep '19

23 Sep '19

On 2019-09-20 8:55 a.m., ac via talk wrote: > > Your sent email, came in marked as SPAM, and I wondered why... Don't forget: we had to implement Reply-To munging, otherwise mailing list messages were going out with incorrect DKIM information. Yes, about now someone usually quotes Chip Rosenthal's decade+ out-of-date article, but you either mess with headers or roughly ⅔ of your list recipients don't get e-mail. Most of them don't even get to see it as spam, either, as gmail et al quietly eat messages with bad DKIM information. cheers, Stewart

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August 2019 meeting videos
by Alex Volkov 22 Sep '19

22 Sep '19

Hello everyone, Here are the videos from our August 2019 lightning talks as a playlist -- https://www.youtube.com/playlist?list=PLUgE6dqIXiEuYoN9o1Jf0Zb2WLqKYHiHY Here are individual lightning talks: Art of Open Source with Dan Tapper -- https://www.youtube.com/watch?v=nS43PZm7pGo Recent Developments in Open-Source Assistive Technology with Stewart Russell -- https://www.youtube.com/watch?v=CyG76wo0JcU GPU computing in Debian with Alex Volkov -- https://www.youtube.com/watch?v=eMu7ynAwECY Our corporate (=tiny) Synology Data Centre with Ron Grimes -- https://www.youtube.com/watch?v=zSqiZwpLdQ4 JPEG with Seneca Cunningham -- https://www.youtube.com/watch?v=sbK8EE6D4YU Alex.

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480GB SSD for $60?
by William Park 22 Sep '19

22 Sep '19

What's going on in SSD market? https://www.canadacomputers.com/product_info.php?cPath=179_1088&item_id=139… -- William Park <opengeometry(a)yahoo.ca>

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Custom build: Which case?
by William Park 21 Sep '19

21 Sep '19

I built all of my computers, last one being a basic i3-4170. There is one part that I was never satisfied with, and that is "computer case". Selections at Canada Computers and Newegg are disappointing. If you were building a full-tower computer, which case would you buy? And where? -- William Park <opengeometry(a)yahoo.ca>

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Finding Old Memory
by Ivan Avery Frey 20 Sep '19

20 Sep '19

I'm looking for 2 GB single DDR 400 unbuffered ECC memory. Does anybody have such memory? Thanks, Ivan.

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Linux kernel 5.3.0
by William Park 20 Sep '19

20 Sep '19

I just tried kernel 5.3.0, and it's noticeably faster in opening windows. Not sure about overall throughput, though. -- William Park <opengeometry(a)yahoo.ca>

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