nutmeg's blog

What I hated about my sqeeeze upgrade experience - udev

Rant follows.

I have upgraded my PC to squeeze this weekend. While this generally worked fine, udev (version 160-1) made my day. As usual I had not read the release notes previously and was hit by

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

dpkg to the rescue:

dpkg -i /var/cache/apt/archives/linux-base_2.6.32-21_all.deb 
dpkg -i /var/cache/apt/archives/linux-image-2.6.32-5-amd64_2.6.32-21_i386.deb  /var/cache/apt/archives/linux-image-2.6-amd64_2.6.32+28_i386.deb 
reboot

Afterwards the upgrade succeded. (For reference: The correct solution would probably have been to run apt-get install linux-image-2.6-amd64 and rebooting, before starting the dist-upgrade.)

udev was not finished with me, though, the syntax for udev rules has changed again. ("NAME="%k" is ignored, because it breaks kernel supplied names", "SYSFS{}= will be removed in a future udev version, please use ATTR{}=", "BUS= will be removed in a future udev version, please use SUBSYSTEM=", etc.) So I started googling and rewriting my custom rules for USB-sticks and USB cardreader. After many reboots (the only way to test these rules nowadays), thing were still not working.

My cardreader is not an exotic but a common one, i.e. it does not report media changes. (The guide for writing udev rules shares this opinion.) Previously I had:

BUS=="scsi", KERNEL=="sd*", SYSFS{model}=="Compact Flash",SYSFS{vendor}=="Generic-",NAME{all_partitions}="cardreader/cf"

which caused udev to generate /dev/cardreader/cf1, /dev/cardreader/cf2, etc. on bootup (without media present), enabling me to configure /etc/fstab to allow mounting of /dev/cardreader/cf1 without superuser privileges. After googling I ended up with this new rule:

SUBSYSTEMS=="scsi", KERNEL=="sd*", DRIVERS=="sd", ATTRS{vendor}=="Generic-", ATTRS{model}=="SD/MMC          ", SYMLINK+="cardreader/sd%n", OPTIONS+="all_partitions"

and while I get ...

argenau:~# ls -l /dev/cardreader/sd
lrwxrwxrwx 1 root root 6 Sep 19 14:42 /dev/cardreader/sd -> ../sdd

... there is still no /dev/cardreader/sd1 (unless I insert a card and run fdisk -l /dev/cardreader/sd as superuser). Looks like OPTIONS+="all_partitions" is ignored. And indeed I find this in udev's changelog:

udev 152
[...]
The option "all_partitions" was removed from udev. This should not be needed for usual hardware. Udev can not safely make assumptions about non-existing partition major/minor numbers, and therefore no longer provide this unreliable and unsafe option.

Joy. Thanks udev for telling me consumer devices have been fixed overnight, USB cardreaders have suddenly started reporting media change events.