January 2020 - luv-main

Re: Weird boot issue
by Craig Sanders 13 Jan '20

13 Jan '20

On Sun, Jan 12, 2020 at 04:20:42PM +1100, pushin.linux wrote: > > -------- Original message --------From: Craig Sanders via luv-main <luv-main(a)luv.asn.au> Date: 11/1/20 2:12 pm (GMT+10:00) To: luv-main(a)luv.asn.au Subject: Re: Weird boot issue On Fri, Jan 10, 2020 at 05:01:57PM +1100, pushin.linux wrote:> Hi all,I am in a great dilemma, when rebooting after agreeing to a> software update, did not check the packges involved, but running Ubuntu> 18.04, I was confronted with this:>> GRUB version 2.02> Minimal BASH-like line editing is supported.>> For the first word, TAB lists possible command completions. Anywhere else> TAB lists possible device or file completions.>> grub> _ ( flashing cursor)> Don't know what to do here.There's an old (2014) but still pretty good tutorial here:https://www.linux.com/tutorials/how-rescue-non-booting-grub-2-linux/see also:https://help.ubuntu.com/community/Grub2/TroubleshootingAlternatively, you could boot with a rescue CD or USB stick, and examine thedrives and partitions with fdisk or gdisk or similar in order to identify theroot filesystem (and the /boot filesystem if it's separate from the root fs).Then mount the root fs as, say, "/mnt", /boot as "/mnt/boot" (if separate),and optionally other filesystems (you probably won't need other partitionsmounted for the rescue operation).Then bind-mount the pseudo-filesystems /dev, /proc, and /sys under /mnt.These are needed for update-grub to work. Here's a quick way to do that: for i in proc dev sys ; do mount -o bind "/$i" "/mnt/$i" ; doneRun "chroot /mnt" to get a shell where /mnt is treated as the root fs.Then you can edit your /etc/default/grub (if needed - e.g. make sure that theline "GRUB_DISABLE_LINUX_UUID=true" is commented out), and run "update-grub".Finally, exit the chroot, unmount the partitions you mounted (in roughlyreverse order to the order you mounted them - e.g. "umount /mnt/dev" beforetrying to "umount /mnt"), and reboot. something like this should work: for i in proc dev sys boot / ; do umount "/mnt/$i" ; doneDue to paranoia and ancient & long-obsolete habit, I like to run "sync" tomanually flush all buffers to disk before rebooting. e.g. "sync ; shutdown -rnow". It's harmless and useless when doing a clean reboot with "shutdown",but may prevent or reduce fs corruption if you have to do a forced reboot(e.g. with "reboot -f") or power-cycle.> I am running an ssd as sda, sdb and sdc are in a btrfs RAID array. Puzzled> by this behaviour.I don't know if this is related to your boot problem or not, but this is thewrong way to think about drives in linux.Drives MAY (and often do) retain the same device names (/dev/sda, /dev/sdb,/dev/sdc etc) when you reboot a machine, but you can NOT rely on that beingthe case.These device names are NOT guaranteed to survive across reboots. In fact, itis has been documented for many years that these device names are not constantor reliable.Storage devices may get different device names for a variety of reasons,including (but not limited to): drives (including USB drives) being added orremoved, new kernel version, module load order, minor timing differences fordrives spinning up or being detected by the kernel, and more.This is why you should always configure grub and /etc/fstab to use UUIDs orLABELs rather than hard-coding /dev/sdXn device names.craig--craig sanders <cas(a)taz.net.au>_______________________________________________luv-main mailing listluv-main@luv.asn.auhttps://lists.luv.asn.au/cgi-bin/mailman/listinfo/luv-mainHi Craig,I am wading through the first option "how to rescue..."I have found rootgrub> ls (hd0,3)/@/ @/homeand ran this ...ls (hd0,3)/@/dev/ run/ boot/ a whole lot of stuff ... inc vmlinuz and home/ and root/grub> ls @/boot/# whole lot of stuff including vmlinuz-4.15.0-74-genericI cant seem to get the syntax right in line 2 for the location of the kernelLine one worked OK, but should I be using root=/dev/sda3 ?I am writing this with one finger on a tablet. I can't read that mess. i'm not even going to try deciphering it. Also, this should be sent to the mailing list, not to me personally. so I'm replying back to the list. craig

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Weird boot issue
by pushin.linux 12 Jan '20

12 Jan '20

Hi all,I am in a great dilemma, when rebooting after agreeing to a software update, did not check the packges involved, but running Ubuntu 18.04, I was confronted with this: GNU GRUB version 2.02Minimal BASH-like line editing is supported. For the first word, TAB listspossible command completions. Anywhere else TAB listspossible device or file completions.grub> _ ( flashing cursor)Don't know what to do here.I am running an ssd as sda, sdb and sdc are in a btrfs RAID array.Puzzled by this behaviour.Any help appreciatedAndrew GreigSent from Samsung tablet.

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Links: file I/O into pipe I/O with /dev/fd, Hot Chips RISC-V tute video
by Rodney Brown 06 Jan '20

06 Jan '20

https://www.spinellis.gr/blog/20191214/ Convert file I/O into pipe I/O with /dev/fd Some Unix commands read data from files or write data to files, without offering an obvious way to use them as part of a pipeline. How can you write a program to interact with such a command in a streaming fashion? This would allow your program and the command run concurrently, without the storage and I/O overhead of a temporary file. You could create and use a named pipe, but this is a clunky solution, requiring you to create and destroy a unique underlying file name. Here's a better approach. Modern Unix systems offer a virtual device directory named /dev/fd/. The files in it correspond to the file descriptors of each process. ... https://www.youtube.com/watch?v=nPXdbm9lc3A Hot Chips Tutorial2: RISC-V 2019-08-18 This tutorial provides an introduction to the RISC-V open ISA, the software development ecosystem built around it, and two open-source cores that have been created to use it. Overview of the RISC-V ISA Krste Asanovic, UC Berkeley Overview of RISC-V SW Ecosystem Bunnaroath Sou, SiFive Overview of Open Source Cores I: Rocket/BOOM Howard Mao and Jerry Zhao, UC Berkeley Overview of Open Source Cores II: Pulp Fabian Schuiki, ETH Zurich

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BlueHackers crowd-funding free psychology services at LCA and other conferences
by Arjen Lentz 01 Jan '20

01 Jan '20

Hi all, and a happy new year! BlueHackers has in the past arranged for a free counsellor/psychologist at several conferences (LCA, OSDC). Given the popularity and great reception of this service, we want to make this a regular thing and try to get this service available at every conference possible – well, at least Australian open source and related events. Right now we’re trying to arrange for the service to be available at LCA2020 at the Gold Coast, we have excellent local psychologists already, and the LCA organisers are working on some of the logistical aspects. Meanwhile, we need to get the funds organised. Fortunately this has never been a problem with BlueHackers, people know this is important stuff. We can make a real difference. (BlueHackers hasn’t yet completed its transition from OSDClub project to Linux Australia subcommittee, so this fundraiser is running in my personal name. Well, you know who I (Arjen) am, so I hope you’re ok all with that.) We have a little over a week until LCA2020 starts, let’s make this happen! Thanks. You can donate via MyCause: https://www.mycause.com.au/page/219883/bluehackers-funding-free-psychology-… please donate and help spread the word. https://bluehackers.org/2020/01/01/bluehackers-crowd-funding-free-psycholog… Twitter @BlueHackersOrg Regards, Arjen.

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