luv-main September 2014

luv-main@luv.asn.au

37 participants
27 discussions

Re: Root filesystem unexpectedly remounted in read-only

by Peter Ross

From: "Tim Connors" <tim.w.connors(a)gmail.com> > On Fri, 19 Sep 2014, Craig Sanders wrote: >> On Thu, Sep 18, 2014 at 10:48:00AM +0200, Michele Bert wrote: >> > 1) Can bad block appear on a virtual disk too? Even if it is >> > eventually just a flat file in the host filesystem? >> > 2) Are those bad blocks related to real bad blocks on the physical >> > host file system? > vmware will tend to drop disk paths well before linux would have a problem > with them, in the name of High Availability. Whilst Linux would just log > a 120s hangcheck timer alert to the syslog if the disk didn't answer in > 120 seconds, vmware might respond to the same disk outage by I have seen the same with Oracle VirtualBox. The "disk" was an ordinary file. The write timed out so Linux (the same Ubuntu 12.04) perceived it as a disk failure and remounted read-only. There were no physical hardware errors involved. It caught me by surprise when it happened and it took a little bit until I understood what's going on. The system just behaved weird (it was only one of three virtual disks so the system worked partially) I have a nagios/Icinga script checking the expected mounts since then. It compares the mounts with a mount "snapshot" written in a file after installation. Regards Peter

8 years, 6 months

Hilbert Curves In Python

by David Zuccaro

Hi, I have been learning python and I have recently written a little program that creates Hilbert curves which I submit to this list for critique and review: # Hilbert Curve # David Zuccaro # 18/09/2014 import sys import pygame import math class cursor: def __init__(self, a): # a should be a list of 2 numbers ie a point. self.a = a def line(self, a): # draw a line from he current position from the new position; update current position pygame.draw.lines(window, (255, 255, 255), True, [[self.a[0], self.a[1]], [self.a[0] + a[0], self.a[1] + a[1]]], 1) self.a[0] = self.a[0] + a[0] self.a[1] = self.a[1] + a[1] def hilbert(self, kind, order): row = ((1,0,0,2), (0,1,1,3), (3,2,2,0), (2,3,3,1)) # hilbert curve definition table 0 = A 1 = B ... dir = ((0,3,2), (3,0,1), (1,2,3), (2,1,0)) # definition of A, B, C, D orient = ((0,-1), (-1,0), (0,1), (1,0)) # definition of up, left, down, right dist = 30 # length of segment if order > 0: for j in range(4): self.hilbert(row[kind][j], order - 1) # keep on hilberting until order = 0 if j < 3: self.line([x * dist for x in orient[dir[kind][j]]]) #this was the previous code but I thought it would be cleaner if # more abstruse to do this all in one line ^ # if dir[kind][j] == 0: # self.line(0, -dist) #up # if dir[kind][j] == 1: # self.line(-dist, 0) #left # if dir[kind][j] == 2: # self.line(0,dist) #down # if dir[kind][j] == 3: # self.line(dist, 0) #right pygame.init() #create the screen window = pygame.display.set_mode((1900, 1000)) david = cursor([10,970]) # starting point increasing y moves down screen david.hilbert(0, 5) # create a fifth order hilbert curve #draw it to the screen pygame.display.flip() #input handling (somewhat boilerplate code): while True: for event in pygame.event.get(): if event.type == pygame.QUIT: sys.exit(0) #end Output is here: http://members.optuszoo.com.au/~david.zuccaro/hilbert2.png https://en.wikipedia.org/wiki/Hilbert_curve

8 years, 6 months

Root filesystem unexpectedly remounted in read-only

by Michele Bert

Hello. I am working on an Ubuntu 12.04, virtualized by a VMWare server, usually through a remote desktop protocol (see xrdp) or a simple ssh connection. This machine which is rebooted very rarely (basically only when there is an updates which needs a reboot to be applied). This morning, when I've reconnected to rdp session, I found that the root was mounted readonly (visible from the /proc/mount, becouse /etc/mtab was not up to update). After a reboot, and a filesystem check all seems to work, but it was quite a curious situation! Searching on the web I found that it happens tipically when kernel finds bad blocks on the disk, but since it's a virtual disk, I have some question. 1) Can bad block appear on a virtual disk too? Even if it is eventually just a flat file in the host filesystem? 2) Are those bad blocks related to real bad blocks on the physical host file system? Thanks in advance for any answer. -- Mick

8 years, 6 months

Getting the Linux console to ignore a usb remote control?

by Paul Dwerryhouse

Hi all, I'm connected an mceusb remote control to a Raspberry Pi and plan to use it to control my audio system. I'm directly reading data from /dev/input/event0, which is all well and good (can't be bothered with lirc, it's too much trouble). The one catch to this is that the mceusb remote appears to the system as a keyboard, so while I'm pressing keys, they will be also going to the system console, and I can see from syslog that these keypresses are going to /bin/login (obviously): Sep 16 07:22:47 tart login[31297]: FAILED LOGIN (1) on '/dev/tty1' FOR 'UNKNOWN', Authentication failure This is less than ideal, so can anyone think of any way to stop the usb remote from being seen as a keyboard, or to get the system to ignore it? I'm not running X on the system, it's just a console-based. Cheers, Paul -- Paul Dwerryhouse paul(a)dwerryhouse.com.au

8 years, 6 months

Re: Trouble booting up Ubuntu 14.04 Live CD in Laptop with UEFI

by Douglas Ray

... On 15/09/14 6:03 AM, Wen Lin wrote: > With further googling, I came across this URL: UEFI Installing - Tips > http://ubuntuforums.org/showthread.php?t=2147295 > > It has lots of tips about all things Ubuntu install/dual-boot under > UEFI, secure boot, etc. One section, titled: *Black Screen/ Video Modes* Thanks for passing on the research! cheers, Douglas

8 years, 6 months

Re: MIME weirdness? [was: Trouble booting up Ubuntu 14.04 Live CD in Laptop with UEFI]

by Erik Christiansen

On 15.09.14 10:38, Trent W. Buck wrote: > Wen Lin <vwenlin(a)gmail.com> writes: > > > This usually required with AMD or nVidia > > <200b>, suggested kernel parameters: > > <200b>in place of quiet splash > > <200b>, adding<200b> > > > > acpi_osi=Linux acpi_backlight=vendor > > > > <200b>And it worked after that! > > I read this list via gmane, and the above looks weird there: > http://article.gmane.org/gmane.org.user-groups.linux.luv.general/4108 > > It looks the same in my newsreader. > > At first I thought there were inline multipart MIME objects > (e.g. between "parameters:" and "in place of"), but what looks like an > underscore in Emacs is apparently a ZERO WIDTH SPACE (0x200B, or  > in the HTML link above). Looking at the post in mutt, a whole bunch of those "=E2=80=8B"¹ whatsits occur in both the text/plain and text/html components of the message. Curiously, they are invisible in mutts pager, but five of them appear (in a highlight colour) as "<200b>" in the quoted text above, in vim as I compose this reply. To render them at your end, I've converted each to its 6 character rendering here. There seems to be one immediately before or after every newline terminating a non-blank line - almost. One blank line seems to have caused the whatsit on the "acpi_osi=" line to occur early. My guess is that the text was generated with some sort of M$ product. (So perhaps, as in daily life now, we should be alarmed but not alert.) Erik ¹ That's "= E 2 = 8 0 = 8 B", without spaces, in case mail agents perform contortions on it. -- At the Victorian [era] version of the X Factor, the talent show format was stripped right back to its bare bones. Just six contestants and a stage, each and every man singing his heart out to impress the judges. While carrying a pig. http://www.bbc.com/news/blogs-magazine-monitor-28982145-

8 years, 6 months

Re: Trouble booting up Ubuntu 14.04 Live CD in Laptop with UEFI

by Daniel J Jitnah

Hi Wen Good to hear.!! I never heard of that Linux boot parameter before - will definitely remember that! As a matter of fact, I did my first installation of first Ubuntu on a brand new Windows 8 laptop last night! Oh I hate that!!! But still your experience (Wen) was more traumatic!! I am now convinced that this UEFI stuff is all a plot to make Linux (or anything else) hard to install on a machine with Windows 8+ preinstalled!!! It should never be that hard!! I have to say it was easier than your (Wen's ) case in the end but still wasted too much time - while pre-UEFI I could easily claim to be able to install Ubuntu (or most distros) with 30 mins ... now it is taking at least 3-4 hrs ... and 80% of the time is just figuring out how to boot the thing reliably to complete the installation!. My case was a ASUS X551 Series. For those interested it works very well once Ubuntu is installed - cheap sub $400 machine (at Center Com, bit more expensive elsewhere with slightly different CPU option), 4 core Pentium CPU, 4 gb ram, 500 hd, 15.6 screen, *intel* graphics, very basic model - but I rate as good value for someone wanting a basic machine for basic word processing, email etc. Surprisingly light to carry around. As a matter of fact my own 13 inch screen also ASUS of similar specs and chassis/case construction but 1 yr old is noticeably heavier. The Intel graphics meant no graphic issue. Biggest issue was to figure how to boot from a USB!!.. It took me 3 hrs of searching the internet, playing with bios option etc to try to boot from USB...and I am disappointed to have to say ... I could not find out how to do that! Whatever I tried, it always booted into Windows 8, even to the extent of disabling the boot device in the bios, it defaulted to re-activating it to boot somehow. But booting from a CD actually worked!!! However, at first with Secure boot on the installation crashed with a kernel panic somewhere during the installation process. And this was inconsistent, as on 2 or 3 attempts it seemed to crash at different stages of the installation. Its possible that when I restarted after a crash, it sees that some files had already been installed and therefore it did not do a full restart, and hence the crash appeared to be at a different stage, but I am not sure about that? But after disabling secure boot, it all just worked fine and completed and after a post install reboot, everthing worked perfectly! Got to say here that Windows 8 was wiped out completely. There was no attempt to do a dual boot at all. Reading the various posts, it appears to be the inconsistency of experience by people that is the problem. I can see why many people would just not bother. It is NOT simply a matter of disabling secure boot in the bios. There seem to be always many things else that need to be fiddle with and each manufacturer now seems to add their own obscure bios option or rename one with a different name just to confuse all. As a comparison, about 1 year ago, I did an install on another ASUS laptop (mine) with Win 7 preinstalled but it has UEFI/secure boot on. It was just a matter of disabling secure boot and on it went smoothly. Your link below (http://ubuntuforums.org/showthread.php?t=2147295), just shows what it mess it can be now!!!! I had assumed that booting off USB was a given on all machine these days, and only required a bios change at most, but it seems that it not the case anymore. The machine above (ASUS X551 series) does not seem to have an option to enable usb boot?? (However a particular web post referred to a particular option and even had a screen shot, but that screen was different to the one I had - it was a X551ca (or va?) - you'd think its also a X551 series machine - even here there seem to be inconsistencies) Daniel On 15/09/14 06:03, Wen Lin wrote: > Hi, > > Finally, got a fix to my dual-boot problem! > > With further googling, I came across this URL: UEFI Installing - Tips > http://ubuntuforums.org/showthread.php?t=2147295 > > It has lots of tips about all things Ubuntu install/dual-boot under > UEFI, secure boot, etc. One section, titled: *Black Screen/ Video Modes* > This usually required with AMD or nVidia > , suggested kernel parameters: > in place of quiet splash > , adding > > acpi_osi=Linux acpi_backlight=vendor > > And it worked after that! > > Subsequent to that, I was able to boot the Ubuntu 14.04 64-bit LiveCD > from the Win 8.1 laptop, with secureboot disabled, but stayed in UEFI. > Installation after that also went without any problem. After that, I > was able to boot into either the Ubuntu, or the Win 8.1, and back, no > worries, even with cold boot. > > I did try to re-enable the Secure Boot, but then I wasn't able to boot > into Win 8.1 after that. So looks like I will need to stick with > secure boot disabled from now on. > > It would seem this solution is an obscure one - I only just came > across it by chance. And don't quite understand what it does either - > just that it worked! > > Thanks Daniel and Douglas for your tips and suggestions. Much > appreciated! Also share my experience here so next time others who > try can waste less time. :-) > > > Wen > > > > > On Mon, Sep 8, 2014 at 12:11 AM, Douglas Ray <dougray(a)cpan.org > <mailto:dougray@cpan.org>> wrote: > > > > On 7/09/14 11:59 PM, Douglas Ray wrote: > > Hi Wen Lin, > > did you try "vbeinfo" at the GRUB prompt? > > ... there's also > http://lists.gnu.org/mailman/listinfo/help-grub > > > cheers > > Douglas > > > > On 6/09/14 5:14 PM, Wen Lin wrote: > >> Hi, > >> > >> I've been trying for weeks to install Ubuntu 14.04 onto my > friend's new > >> Toshiba laptop with the new UEFI secure boot built-in. So far, > no luck! > >> I can't even boot it up with the Ubuntu Live CD, regardless of > >> SecureBoot enabled or disabled. > >> > >> First, some info and what I had done so far: > >> > >> Laptop: Toshiba Satellite C50D-A > >> (My friend bought from JB Hifi for $480 - not a high-end machine) > >> CPU: AMD E1-1200 APU with Radeon HD Graphic 1.4 GHz 64-bit > >> Memory: 4 GB > >> HD: 500 GB > >> Display adapter: AMD Radeon HD 7310 Graphic > >> OS: Windows 8 (I had since upgraded it to Win 8.1) > >> > >> I had: > >> - Created a Win System Recovery image (using Win 8.1 built-in > standard > >> tool) to a USB flash disk. > >> - Also used Win 8.1 built-in tool to shrink the C: drive to 255 GB, > >> leaving me the other half of the disk for my Ubuntu install. > >> > >> I had no problem F2 at startup into the laptop's BIOS to change > stuff like: > >> - Boot sequence > >> - Enable/Disable SecureBoot > >> - Swap between UEFI Boot & CSM Boot (or Legacy mode) > >> > >> I had googled around quite a lot, and had tried several different > >> approaches suggested, to no avail. > >> > >> Most of the forum sites/blogs suggest disable SecureBoot, some > said no > >> need - as newer Distro like Ubuntu 14.04 nowadays have no problem > >> booting with SecureBoot on. > >> > >> I tried both approaches, but the Live CD first could only display a > >> text-based version of GRUB 2 boot menu, with "Try Ubuntu" & > "Install > >> Ubuntu" among the menu options (rather than the Ubuntu's usual > graphical > >> one). Then when I selected either the "Try" or "Install" > options, it > >> went into a total blank screen, and a moment later, everything > stop - I > >> tried waiting for it, sometimes hours, but it never come back! > >> > >> To try to see some messages, I used 'e' in the Grub menu to get > into an > >> editing mode: > >> set gfxpayload=keep > >> linux /casper/vmlinuz.efi file=/... boot=casper > quiet splash -- > >> initrd /casper/initrd.lz > >> > >> To edit the kernel boot up parameters - generally involved > replacing the > >> "quiet splash" with parameters like "nomodeset", "vga=radeon", > >> "vga=792", etc - all to no avail. But this time I could see > some boot > >> up messages splashing out, and then stopped at certain point: > >> E.g. > >> - [drm] Initialized radeon 1.34.0 ... > >> - ahci 0000:00:11:0: flags: 64bit ncq ... > >> - r8169 Gigabit Ethernet driver ... > >> - fb: conflicting fb hw usage radeondrmfb vs EFI VGA - removing > generic > >> driver > >> - ACPI: Video Device [VGA] (multi-head: yes rom: no post: no) > >> > >> In general, it would seem the different boot parameters could > only vary > >> in at most several boot steps, but none of them managed to go > all the > >> way to successfully boot into Ubuntu Live. > >> > >> I had also tried other Distros: Ubuntu 13.10 64-bit & Linux Mint 15 > >> Cinnamon 64-bit - no different. I even tried an Ubuntu 12.04 > 32-bit CD > >> - but it boot straight into the Windows 8.1 instead. > >> > >> Another thing to point out: I had also tried the CSM Boot > option (in > >> place of the default UEFI). When in this mode, the whole > "SecureBoot" > >> feature disappeared, and I managed to boot into Ubuntu 14.04 > Live CD, > >> all the local programs, WiFi, Internet, the lots, all worked as > normal! > >> I had not tried installing Ubuntu from there. Just as well! As > >> attempt to boot back to Win 8.1 failed - the error message > basically was > >> saying that the Win 8.1 is not there anymore! I could only > boot back to > >> Win 8.1 normally after I had reverted back to UEFI Boot mode. > >> > >> As you can see, no joy at all! :-( > >> > >> So my question: Is it a UEFI/SecureBoot problem, or an AMD Radeon > >> display adapter problem? If it's a display adapter problem, > then why I > >> could boot into Ubuntu when not in UEFI mode? If it's a UEFI > problem, > >> then why couldn't I boot into Ubuntu with the SecureBoot > disabled (said > >> so by all the related forums & blogs I had visited so far - i.e. > >> secureboot off - no problem)? > >> > >> I was pondering, if all else failed, to just install Ubuntu > 14.04 into > >> the partition I had freed up, while in CSM mode. If this > worked, then I > >> could persuade my friend to just stick to Ubuntu, and > occasionally if > >> wanting to go to Wn 8.1, change back to UEFI before doing so. > While > >> this may work (painfully), my friend might one day decide not > to go back > >> to Ubuntu, and my efforts would be wasted. Worst still, installing > >> Ubuntu in CSM mode may render the Win 8.1 unbootable, and I > don't think > >> my friend want that! > >> > >> Any suggestions, comments, or experience in such dual boot > adventure > >> would be welcomed! > >> > >> Thanks in advance. > >> > >> Wen > >> > >> > >> > >> _______________________________________________ > >> luv-main mailing list > >> luv-main(a)luv.asn.au <mailto:luv-main@luv.asn.au> > >> http://lists.luv.asn.au/listinfo/luv-main > >> > > _______________________________________________ > > luv-main mailing list > > luv-main(a)luv.asn.au <mailto:luv-main@luv.asn.au> > > http://lists.luv.asn.au/listinfo/luv-main > > > > > _______________________________________________ > luv-main mailing list > luv-main(a)luv.asn.au <mailto:luv-main@luv.asn.au> > http://lists.luv.asn.au/listinfo/luv-main > > > > > _______________________________________________ > luv-main mailing list > luv-main(a)luv.asn.au > http://lists.luv.asn.au/listinfo/luv-main

8 years, 6 months

Performance surprise: partitions - raw vs. on top of ZFS

by Peter Ross

Hi all, I am doing some research about "the best way" to give a partition to Oracle. I found this surprising and you may too, it is quite amusing: http://jrs-s.net/2013/05/17/kvm-io-benchmarking/ But here’s the big surprise – if we set up a ZVOL, then format it with ext4 and put a .qcow2 on top of that… it performs as well, and in some cases better than, the raw zvol itself did! As odd as it sounds, this leaves qcow2-on-ext4-on-zvol as one of our best performing overall storage methods, with the most convenient options for management. It sounds like it’d be a horrible Rube Goldberg, but it performs like best-in-breed. Who’d’a thunk it? According to the benchmark you have this layering: - qcow2 (virtual disk) as a file on an - ext4 filesystem formatted on a - zvol created on a - raw partition performing better than a raw partition! But - zvol created on a - raw partition is "not worth the hassle". Any thoughts and experiences? I want to give a disk via iSCSI to Oracle (Avi knows more;-) and look for the best setup. The iSCSI target is FreeBSD which can export files as block devices or zvols or raw disks or mirrored disks or other exotic GEOM devices on top of raw disks. According to the benchmark above, a file exported as a blockdevice on top of a zvol could be better than an exported disk.. Could this be true? Regards Peter

8 years, 6 months

kickstart post-installation script issues

by Bill

Hi There, I have a problem to run the kickstart post-installation script on Red Hat/CentOS. The script is quite simple as follows: %post --log=/root/ks-post.log mkdir /home/tmp cd /root wget -nH http://192.168.1.10/afile -P /root/ %end Basically, I tried to make a directory /home/tmp, and cd to /root and copy a file called "afile" to /root. The log file "ks-post.log" was created correctly, but the /home/tmp was create with a question mark at the end: /home/tmp? The file "afile" was copied to /root/? The log file showed the following error message: cd /root^M No such file or directory I have tried "--nochroot" option and prepend every directory name with /mnt/sysimage/, but I have still got the same issues. Cd to /home/tmp showed cd /home/tmp^M/ Thanks in advance for any help. Cheers, Bill

8 years, 6 months

Shutting down to runlevel 1

by Carl Turney

Hi All, (Thanks for the suggestions for my wifi problems.) Anyone: Any suggestions about the new versions of Ubuntu and Mint crashing when trying to shift from multi-user mode down to single-user mode? (Note: Am NOT talking about booting into runlevel 1.) Systems consistently crash when I give any of these commands (in Ubuntu 14.04.1 and Mint 17)... init 1 telinit 1 shutdown now ... in spite of documentation saying I can do those very things. Am giving them AFTER logging out of any GUI session, and Ctrl-Alt-F1-ing into a REAL TTY CLI. Thanks again, Carl

8 years, 6 months

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luv-main September 2014