Eject disk from dvd drive
Open xterm

root@slitaz: udevadm monitor

Insert dvd in drive
My output in xterm:
KERNEL[1291412461.006695] change /devices/pci0000:00/0000:00:1f.2/host1/target1:0:0/1:0:0:0 (scsi)
KERNEL[1291412461.006896] change /devices/pci0000:00/0000:00:1f.2/host1/target1:0:0/1:0:0:0/block/sr0 (block)
UDEV [1291412461.007870] change /devices/pci0000:00/0000:00:1f.2/host1/target1:0:0/1:0:0:0 (scsi)
UDEV [1291412462.318934] change /devices/pci0000:00/0000:00:1f.2/host1/target1:0:0/1:0:0:0/block/sr0 (block)

This indicates /dev/sr0 is the dvd drive

tux@slitaz: mplayer dvd://1 -dvd-device  /dev/sr0

tux can play dvd if he is a member of cdrom group

mplayer,vlc,etc. have /dev/dvd ,/dev/dvdrw, /dev/cdrom , /dev/cdrw hardcoded into the program this can be configured in the gui of some programs. I discovered /etc/udev/rules.d/70-persistent-cd.rules will make symlinks on boot with these names to pci-0000:00:1f.2-scsi-1:0:0:0 (/dev/sr0)with 777 permissions

tux@slitaz:~$ sudo cat /etc/udev/rules.d/70-persistent-cd.rules
# This file was automatically generated by the /lib/udev/write_cd_rules
# program, run by the cd-aliases-generator.rules rules file.
#
# You can modify it, as long as you keep each rule on a single
# line, and set the $GENERATED variable.

# CDDVDW_SH-S223F (pci-0000:00:1f.2-scsi-1:0:0:0)
SUBSYSTEM=="block", ENV{ID_CDROM}=="?*", ENV{ID_PATH}=="pci-0000:00:1f.2-scsi-1:0:0:0", SYMLINK+="cdrom", ENV{GENERATED}="1"
SUBSYSTEM=="block", ENV{ID_CDROM}=="?*", ENV{ID_PATH}=="pci-0000:00:1f.2-scsi-1:0:0:0", SYMLINK+="cdrw", ENV{GENERATED}="1"
SUBSYSTEM=="block", ENV{ID_CDROM}=="?*", ENV{ID_PATH}=="pci-0000:00:1f.2-scsi-1:0:0:0", SYMLINK+="dvd", ENV{GENERATED}="1"
SUBSYSTEM=="block", ENV{ID_CDROM}=="?*", ENV{ID_PATH}=="pci-0000:00:1f.2-scsi-1:0:0:0", SYMLINK+="dvdrw", ENV{GENERATED}="1"

This file stopped working correctly when I plugged the dvd drive into a different sata port on the motherboard. UDEV thought I had 2 drives installed,link names were appended with 1 (/dev/dvd1)which didn't work.On my frugal install I delete the 70-persistent-cd.rules file and did a tazusb writefs lzma so it wouldn't reappear on reboot. When I rebooted a new file was regenerated by the system that made the correct symlinks to /dev/sr0.

... and people wonder why Linux isn't all that popular as a mass-consumption desktop operating system!I have over 30 years experience in the IT industry and almost all of the above is completely meaningless to me. How is the "ordinary man in the street" supposed to cope when he has a problem with a Linux-based system?

Anyway, I opened a terminal and typed "udevadm monitor", got the couple of lines of useful info, then the cursor sat at the start of the next line. Inserted DVD, drive spun up, then ... nothing. Damaged DVD? Tried another ... exactly the same. Nothing wrong with the DVD drive as I can boot into SliTaz from it quite happily (although my current installation is on the hard drive).

What do I try now?

On Googling the problem yesterday I came across reference elsewhere to the etc/udev/rules.d/70-persistent-cd.rules file, but it doesn't exist on my machine. Where does it come from? Can I just create it with a text editor? The other files in that folder look as though they were auto-generated -- how? By what?

There *is* a 75-cd-aliases-generator.rules file, the contents of which are ...

# these rules generate rules for the /dev/{cdrom,dvd,...} symlinks

# the "path" of usb/ieee1394 devices changes frequently, use "id"
ACTION=="add", SUBSYSTEM=="block", SUBSYSTEMS=="usb|ieee1394", ENV{ID_CDROM}=="?*", ENV{GENERATED}!="?*", \
  PROGRAM="write_cd_rules by-id", SYMLINK+="%c", GOTO="persistent_cd_end"

ACTION=="add", SUBSYSTEM=="block", ENV{ID_CDROM}=="?*", ENV{GENERATED}!="?*", PROGRAM="write_cd_rules", SYMLINK+="%c"

LABEL="persistent_cd_end" 

What's that all about? Any use to me?

My more fundamental question is: How do you Linux gurus get to learn about this stuff? I've bought umpteen "Introduction to Linux" books but half of them stop somewhere around, "Linux is really great. Here are some command-line programs." and the other half start by assuming you've already used Linux for ten years and have a PhD in rocket science. There's nothing for the guy like me who knows WIndows really well, and is trying to find some logic to Linux's apparent total randomness. I really don't like feeling so helpless and having to ask elementary questions on boards like this, but I haven't found a middle way. Can anyone point me to somewhere suitable? At the moment I'm really, really disheartened ... when I found SliTaz I thought "Great! Here's a Linux distro that seems different from all the rest -- not bloatware, not total geekery, clean and functional but easy to use." Unfortunately, I'm finding that it's great until I run into problems, and then it's back into the Linux desert again. Right now, I can't wait until I get my XP installation disk back and I can return to familiar territory where everything just works. Sorry ...

Excellent! :)
The quote I love so much:
Linux is user friendly... It's just picky about who it becomes friends with.

@xmfclick, try smplayer (tazpkg get-install smplayer). smplayer provides a nice gui for mplayer, is very easy to use and rich with features. I ran into the same issues with dvd playing and after messing around with mplayer/vlc/etc. found smplayer to be the best.

Addln tip: When using smplayer, in the Open menu, if you run into issues using the default "DVD from drive" option, simply open pcmanfm, click on the DVD drive. This will mount the contents of the drive into /media/cdrom. Then in smplayer, use the option "DVD from folder" and it works perfectly.

Slitaz, while small and powerful, is definitely not the easiest to use distro out there. If you are new to Linux you might want to try something like Ubuntu or PCLinuxOS. They are a lot more user friendly.

SliTaz is optimised for performance and lightness not for ease of use and that's I like it. This small problems make me think more and discover the wonderful world of Linux. Another distro optimized for ease of use is Mandriva Linux one live. It has even a graphical control center like in windows - mcc. You can manage all your system from a GUI there.

Slitaz points my DVD and CD writer to the same shortcut named cdrom...

If you want powerful and easy Linuxes, try PCLinuxOS and Mint Linux. Both are super powerful, comes with VLC, codecs, flash, firefox, et al pre-installed and if you use Compiz effects and PlayOnLinux (with Wine), it blows Windows out of the water... but go back to Windows if you want to ;)