Ubuntu udev Hacks


...or, Kernel 2.6: Adventures in User-space

From apt-cache show udev :

"udev is a collection of tools and a daemon to manage events received from the kernel and deal with them in user-space. Primarily this involves creating and removing device nodes in /dev when hardware is discovered or removed from the system."

All is well and good, except udev does some configuration on the installation of that package.

  • If you have problems with hardware detection on a new sysetm after restoring (from ghost or pqimgctr images), it's worth running apt-get --reinstall install udev to see if that fixes the problems.

Again from apt-cache show udev :

Events are received via kernel netlink messaged and processed according to rules in /etc/udev/rules.d, altering the name of the device node, creating additional symlinks or calling other tools and programs including those to load kernel modules and initialise the device."

One neat (?) feature I just discovered is /etc/iftab. It is used by udev to programatically force a particular interface to use a particular name, based on the interface's MAC address, which might not otherwise happen by default.

But on an image restore, /etc/iftab had the wrong MAC address forced to eth0, meaning the new machine's only ethernet card was eth1. This explains why.

  • apt-get --reinstall install udev fixed it, as also did emptying/commenting out /etc/iftab .

-- DanielAllen - 15 Aug 2006

Topic revision: r2 - 2008-02-19 - MikeGore
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