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Excessive SCSI logging under Ubuntu

March 18, 2008 By: webmaster Category: Tech Problems, Ubuntu

For some natty reason, my 64bit Ubuntu 8.04 server sometimes insists that a SCSI logging level of infinite detail is good for my health. Which means my messages, syslog and kern.log files get 50-100 lines like this per second:
Mar 18 23:52:25 home kernel: [ 8661.700076] scsi_add_timer: scmd: ffff81004da8a700, time: 7500, (ffffffff88123ed0)
Mar 18 23:52:25 home kernel: [ 8661.700117] scsi_delete_timer: scmd: ffff81004da8a000, rtn: 1
If you too are suffering from this then do the following: 1. First, stop it right now by starting a shell and typing:
sudo sysctl -w dev.scsi.logging_level=0
2. To make sure it doesn't start up again after a reboot then edit the file /etc/sysctl.conf and add this line anywhere in the file:
dev.scsi.logging_level = 0
And you should be all set.

Legacy NVidia Ubuntu woes

March 11, 2008 By: webmaster Category: Technology, Ubuntu

Somewhere along the line, NVidia got a lot stricter in their monitor handling. If you used to be able to run X at high resolutions but all you can get after an upgrade is something like 1024x768 then it is likely that you have been caught by the clock check bug. You typically get lines like these in your Xorg log (/var/log/Xorg.0.log):
(WW) NVIDIA(0): No valid modes for "1920x1200"; removing.
(WW) NVIDIA(0): No valid modes for "1600x1200"; removing.
To get the X server to tell you exactly why it's removing those two modes, try starting X with -logverbose 6 as arguments, and it will log something like this instead:

    (II) NVIDIA(0): Validating Mode "1600x1200":
    (II) NVIDIA(0): 1600 x 1200 @ 60 Hz
    (II) NVIDIA(0): For use as DFP backend.
    (II) NVIDIA(0): Mode Source: EDID
    (II) NVIDIA(0): Pixel Clock : 162.00 MHz
    (II) NVIDIA(0): HRes, HSyncStart : 1600, 1664
    (II) NVIDIA(0): HSyncEnd, HTotal : 1856, 2160
    (II) NVIDIA(0): VRes, VSyncStart : 1200, 1201
    (II) NVIDIA(0): VSyncEnd, VTotal : 1204, 1250
    (II) NVIDIA(0): H/V Polarity : +/+
    (WW) NVIDIA(0): Mode is rejected: PixelClock (162.0 MHz) too high for
    (WW) NVIDIA(0): Display Device (Max: 150.0 MHz).
If this used to work for you, and all you did was upgrade Ubuntu (or some other distro), then edit your /etc/X11/xorg.conf file and add the line
Option         "ModeValidation" "NoMaxPClkCheck"
inside either the Screen or the Device group. Restart X and it should start up in a higher mode again. For more interesting options to set, try looking at the NVidia X driver documentation. Leave a comment if you're lost and I'll try to guide you through the tricky parts.

Ubuntu Hardy upgrade woes

February 20, 2008 By: webmaster Category: Tech Problems, Technology

This week, two showstoppers appeared in the Ubuntu Hardy upgrade system. First one was a botched upgrade of a language package under OpenOffice and the other was a problem related to Python/APT/dpkg.
First one looked like this:
Reading package lists... Done
Building dependency tree       
Reading state information... Done
You might want to run `apt-get -f install' to correct these.
The following packages have unmet dependencies:
  language-support-writing-en: Depends: openoffice.org-hyphenation-en-us but it is not installed
E: Unmet dependencies. Try using -f.
The easy fix out of this one is to start up System->Administration->Synaptics Package Manager and uninstall "openoffice.org-hyphenation". This will trigger a removal of about 85 packages including OpenOffice itself. When that is done, use the same Package Manager to install OpenOffice again and in goes the 85 packages again.
The second one looked like this:
Setting up python-apt (0.7.4ubuntu5) ...
Traceback (most recent call last):
  File "/usr/bin/pycentral", line 1593, in 
    main()
  File "/usr/bin/pycentral", line 1587, in main
    rv = action.run(global_options)
  File "/usr/bin/pycentral", line 982, in run
    self.pkg.byte_compile(bc_option, self.options.exclude)
  File "/usr/bin/pycentral", line 624, in byte_compile
    rt.byte_compile(files, bc_option, exclude_regex)
AttributeError: 'NoneType' object has no attribute 'byte_compile'
dpkg: error processing python-apt (--configure):
 subprocess post-installation script returned error exit status 1
This has now been fixed, and a new python-central should be available at the repositories. I hacked my python-apt to bypass this before the official fix was out, but all you should have to do is update/upgrade as normal and everything will be fine.

Ubuntu Feisty Fawn

January 27, 2007 By: webmaster Category: Technology, Ubuntu

So you want to be a hero. Well, at least you want to be able to run the latest and greatest Ubuntu version. Perhaps you're a Gentoo convert like me, who miss being able to update your system at least four times a day. Just to get that fix. It's like going 10 minutes without getting an email, you send one to yourself just to see if the system is working...

Ubuntu Feisty Fawn 

Aaaanyway, there is really nothing to it. Edit your /etc/apt/sources.list and change all references to edgy to feisty. I.e. replace edgy with feisty throughout the file. Then run apt-get update and  update-manager -c, both as root. You may have to say yes to one or two "are you sure you're willing to destroy your system"-questions, but what the hey. After that, you'll be the proud owner of a bleeding Ubuntu system and you'll be able to do an apt-get update as often as you wish and more or less be guaranteed to get an update every time. Upgrade bliss.

Keeping time in Ubuntu

January 17, 2007 By: webmaster Category: Technology, Tutorials, Ubuntu

For some strange reason, none of my Ubuntu 6.10 installations have included NTP (Network Time Protocol) by default. No idea why, but here is how you make sure the clock your Ubuntu box is staying in sync with the rest of the world if the same thing happens to you.

 # sudo apt-get install ntp-server

This is technically it, but the stock installation does not adjust your time right away if it is way out of sync. So we just do this to make sure we're correct from the start:

# /etc/init.d/ntp-server stop
# ntpdate -s pool.ntp.org
# /etc/init.d/ntp-server start

There, you're in sync and will stay in sync from now on.

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Growing RAID5 sets in Ubuntu

January 10, 2007 By: webmaster Category: Technology, Tutorials, Ubuntu

Growing RAID5 sets under Linux by adding new disks on the fly has been possible for some time now. However, the kernel that comes default with Ubuntu 6.10 does not appear to contain all the needed support to do this. So if you need to do this, as I did, you first need to boot a newer kernel than the one available. I picked 2.6.19 and compiled it using these instructions. That took about five commands in total to do, so I won't repeat those instructions here. Note however, that I had to specifically add support for both RAID5 and my various SATA-cards to the kernel configuration (the make menuconfig part of the instructions). Your mileage may vary.

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