Category Archives: Linux

Intel wifi led blinking AGAIN on Ubuntu 12.04

I previously posted about this on previous versions of Ubuntu, but despite updating the instructions for 11.10 the instructions are once again obsolete. It seems Intel changes the name of its wifi kernel module every release…

On my Dell E4300 with “Intel Corporation WiFi Link 5100” (as reported by lspci), the module name is now “iwlwifi”. This means the kernel options you add to /etc/modprobe.d should be against this module rather than iwlcore (11.04) or iwlagn (11.10).

So the instructions once again:

$ sudo -i
# echo 'options iwlwifi led_mode=1' >> /etc/modprobe.d/wlan.conf
# modprobe -r iwlwifi && modprobe iwlwifi

Bear in mind that the second line removes the wifi kernel module temporarily which will disconnect your wifi. It should automatically reconnect, if not reboot.

Slow desktop performance on Ubuntu 11.10 with nvidia graphics cards

11.10 has been a bit of a mixed bag. On the plus side it has Gnome 3, giving me a practical (and in my opinion superior) alternative to Unity. On the minus side I had upgrade glitches on both my work and personal machines, and they were unrelated issues! Might be wise to wipe and reinstall for this one (you did separate your home partition when you installed didn’t you :)).

Anyway after getting it working on my work PC (which has an 8400GS), the desktop was quite laggy in both Unity and Gnome3. It was still usable but I didn’t realise how bad it was until I went home and noticed how much smoother my laptop was, with its lowly 2009-era Intel integrated graphics…

The solution was to install the latest 285.05 Nvidia driver, but trust me when I tell you that you do not want the hassle of using the Nvidia installer from the Nvidia website.

It is much simpler to use the X Updates ppa.

So assuming you already have the default binary Nvidia driver installed and activated (nvidia-current), the quick command line solution to your performance woes should hopefully be:

sudo -i
add-apt-repository ppa:ubuntu-x-swat/x-updates
apt-get update && apt-get upgrade
reboot

You should notice an update for the nvidia-current package being installed.

That wasn’t too bad was it? :)

How not to troubleshoot an unexplained server reboot

We asked our provider to investigate why one of our servers rebooted last night. In the process they accidentally rebooted it again… this is root’s bash_history just before it happened, note line 971:

  954  2011-08-17_15:10:39 sar -q
  955  2011-08-17_15:10:59 sar -q|less
  956  2011-08-17_15:11:09 sar -r|less
  957  2011-08-17_15:11:24 last -x|less
  958  2011-08-17_15:11:49 history |grep -i shutd
  959  2011-08-17_15:11:21 history
  960  2011-08-17_15:11:32 date
  961  2011-08-17_15:13:52 cd /var/log/
  962  2011-08-17_15:13:53 ls
  963  2011-08-17_15:13:54 ls -lah
  964  2011-08-17_15:13:58 less audit/
  965  2011-08-17_15:14:04 less audit/audit.log
  966  2011-08-17_15:14:25 less secure
  967  2011-08-17_15:15:15 grep -v nagios secure | less
  968  2011-08-17_15:16:11 dmesg
  969  2011-08-17_15:17:57 sar -r
  970  2011-08-17_15:18:19 dmesg
  971  2011-08-17_15:18:30 dmesg | reboot
  972  2011-08-17_16:20:20 [LOGOUT]: xxxx     pts/2        2011-08-17 15:27 (xxx.xxx.xxx.xxx)

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Stopping the Intel WiFi LED from blinking in Ubuntu

My Dell E4300 has an Intel 5100 wifi card and the led blinks constantly. I still don’t understand how Intel can consider blinking the wifi LED during data transfer to be a sensible default. For most people it blinks non-stop which is both uninformative and irritating.

Fortunately blogger Alex Cabal found a solution for Karmic, and his updated solution also works for Natty/11.04. It describes opening a text editor and pasting a couple of lines, however I’m much lazier so here’s the one-line version:

echo 'options iwlcore led_mode=1' >> /etc/modprobe.d/wlan.conf

Of course, the command above must be run as root (sudo -i), for some reason sudo gave me access denied. You also need to reboot… or you could just unload and reload the module:

modprobe -r iwlagn && modprobe iwlagn

The double ampersand just executes the next command if the previous one succeeded (exit status 0).

Update

As of Ubuntu 11.10 (kernel 3.0.0) the option has to be applied to the iwlagn module, options for iwlcore are ignored. Thus the full solution now becomes:

sudo -i
echo 'options iwlagn led_mode=1' >> /etc/modprobe.d/wlan.conf
modprobe -r iwlagn && modprobe iwlagn

Keyboard layout switching to USA in Ubuntu 11.04

I recently upgraded the keyboard in my Dell E4300 from a standard USA model to a backlit UK model. All went great however I noticed that the keyboard layout kept switching back to the USA layout. It seemed to happen after every reboot, and also randomly in the middle of the session.

There’s even a bug in launchpad about it which I commented on: https://bugs.launchpad.net/ubuntu/+bug/762111

There were two factors causing the layout to switch and the USA layout to be reinstated.

Firstly when logging in the session was set to the USA layout. To fix this logout, select your user name and then look for the keyboard symbol down the bottom of the screen.

The second feature causing seemingly random switches during sessions was the “Separate layout for each window” option in Keyboard Preferences (Keyboard Preferences is in system settings and the option is on the layout tab).

If you deactivate this, remove the USA layout, apply system wide and make sure the GDM session is set to the correct layout on login you shouldn’t have any more problems with randomly switching keyboard layouts!

Getting the most out of Terminator

Terminator in action

Terminator is a must-have tool for Linux administrators. It’s a terminal emulator that supports multiple terminals via tabs, but also by dividing up its window with horizontal and vertical splits.

The user documentation is a bit sparse, in fact what you see in the man page is what you get. In this post I’ll take you through the features that I think make Terminator the best terminal emulator around.
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Setting up a secure Ubuntu LAMP server

Disclaimer: This article is provided for your information only, and simply following this guide will not make your server “secure”. As the server administrator you are ultimately responsible for its security!

Intro

Having recently been through the process of setting up a few Ubuntu LAMP (Linux, Apache, MySQL, PHP) servers lately I thought I’d make an article out of my notes and provide a starters guide to setting up the LAMP stack on Ubuntu.

It goes without saying that the only truly secure computer is one with no network connection, no ports or input devices and is locked in a bank vault, but such a machine is not terribly useful. Regretfully, compromises must be made to allow functionality! Besides presuming insecurity, there are a lot of things you can do to make your server more secure and keep out the vast majority of would-be hackers running port scans, meta-exploit scripts and dictionary attacks.
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A quick look at Unity in Ubuntu 11.04

I usually jump on the latest Ubuntu release before it hits the final release stage, but this time it was with a bit more trepidation than usual. You see they’ve replaced the shell with a completely new one – Unity. And to say that not everyone likes it would be a minor understatement.

The good news is that Unity is undoubtedly a step forward in practical user interface terms. The classic Gnome panel is really showing its age, and doesn’t lend itself to wide screen formats due to having panels on both the top and bottom of the screen. SUSE addressed this by created a start menu like launcher, but it was always a bit clunky and barely an improvement over Windows XP.

So how is Unity different? It is perhaps more informative to talk about how it is similar…
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