devfs newbie: dissapearing or somtimes not created cdrom

[C R Johnson <iamcliff@xxxxxxxxxxxxx>]

I am using the SGI xfs kernel 2.4.2-SGI_XFS_1.0smp with devfs.

If I boot with a cdrom in the drive, the system comes up with the drive 
mounted and working.
If I boot without a cdrom in the drive, I get no entry in /dev/cdroms, 
and hence no working cdrom.
Likewise if I unmount a cdrom after booting and leave the drive empty 
for a number of hours, the device /dev/cdroms/....
vanishes and I am once again without my cdrom drive.

What do I have to do to either keep the device from dissapearing or how 
do I (re-)create it in the event it does not exist.
This does not seem to be in the FAQ.

Thanks for a clue,

Cliff