One of my Slackware systems has two optical drives: Blu-Ray and DVD:
/dev/sr0 and /dev/sr1. In 14.2 as well as current, if neither are used
for awhile, some of the udev symlinks to /dev/sr0 disappear. This
becomes maddening (as in WTF?) when I'm trying to run my qemu VMs and
I get the error:

Could not open '/dev/dvd': No such file or directory

Taking a peek shows:

$ ls -l /dev/dv*
lrwxrwxrwx 1 root root 3 Mar 14 14:32 /dev/dvd1 -> sr1
lrwxrwxrwx 1 root root 3 Mar 14 14:32 /dev/dvdr1 -> sr1
lrwxrwxrwx 1 root root 3 Mar 14 14:32 /dev/dvdrw1 -> sr1
lrwxrwxrwx 1 root root 3 Mar 14 14:32 /dev/dvdwriter1 -> sr1

instead of the expected list:

$ ls -l /dev/dv*
lrwxrwxrwx 1 root root 3 Mar 19 19:00 /dev/dvd -> sr0
lrwxrwxrwx 1 root root 3 Mar 19 19:00 /dev/dvd0 -> sr0
lrwxrwxrwx 1 root root 3 Mar 19 19:00 /dev/dvd1 -> sr1
lrwxrwxrwx 1 root root 3 Mar 19 19:00 /dev/dvdr -> sr0
lrwxrwxrwx 1 root root 3 Mar 19 19:00 /dev/dvdr0 -> sr0
lrwxrwxrwx 1 root root 3 Mar 19 19:00 /dev/dvdr1 -> sr1
lrwxrwxrwx 1 root root 3 Mar 19 19:00 /dev/dvdrw -> sr0
lrwxrwxrwx 1 root root 3 Mar 19 19:00 /dev/dvdrw0 -> sr0
lrwxrwxrwx 1 root root 3 Mar 19 19:00 /dev/dvdrw1 -> sr1
lrwxrwxrwx 1 root root 3 Mar 19 19:00 /dev/dvdwriter -> sr0
lrwxrwxrwx 1 root root 3 Mar 19 19:00 /dev/dvdwriter0 -> sr0
lrwxrwxrwx 1 root root 3 Mar 19 19:00 /dev/dvdwriter1 -> sr1

Rebooting or reloading the udev rules (as root) restores the expected
symlinks:

# udevadm control --reload-rules && udevadm trigger

I suppose I could just tell qemu to look at /dev/sr0, but where's the
fun in that?