udev doesn't create the /dev/cdrom symlinks

[Stefan Monnier <monnier@iro.umontreal.ca>]

My old trusty Thinkpad X30 has a problem: the CDRW/DVDR device that's
plugged into the ultrabay only appears as /dev/hdb (or even /dev/hdc
sometimes), but not as /dev/cdrom.

I've been using Debian testing on it for 3 years now with much joy.  I don't
often use the CD device, but I do remember it appearing as /dev/cdrom some
time in the past.
Also my desktop Debian testing system has its CD device appearing as
/dev/cdrom just fine.

I looked at the rules files in /etc/udev/rules.d but couldn't quite
understand how/when the z25-persistent-cd.rules (which is properly filled on
my desktop but not on my Thinkpad) is supposed to be built.

How would I start debugging this?


        Stefan