I was on Debian Lenny and needed to get to CUPS 1.4.2 or above which required an upgrade to Debian Squeeze. During the apt-get dist-upgrade, I ran into this snag:
Preparing to replace udev 0.125-7+lenny3 (using .../archives/udev_151-3_i386.deb) ...
Since release 150, udev requires that support for the CONFIG_SYSFS_DEPRECATED
feature is disabled in the running kernel.
Please upgrade your kernel before or while upgrading udev.
AT YOUR OWN RISK, you can force the installation of this version of udev
WHICH DOES NOT WORK WITH YOUR RUNNING KERNEL AND WILL BREAK YOUR SYSTEM
AT THE NEXT REBOOT by creating the /etc/udev/kernel-upgrade file.
There is always a safer way to upgrade, do not try this unless you
understand what you are doing!
dpkg: error processing /var/cache/apt/archives/udev_151-3_i386.deb (--unpack):
subprocess new pre-installation script returned error exit status 1
No matter what I tried, including trying to use various calls to aptitude, it refused to let me get past it. I even tried doing what it said to do by upgrading the kernel, but it still kept coming back with that error message.
I ended up giving in and just downloading the Debian 5.0.4 Network Install CD ISO's and reloading it from scratch. So, this post is to warn others that the Debian dist-upgrade from Lenny to Squeeze is broken by udev.