[Discuss] Fedora 28 Doesn't See External DVD Drive on USB Port

[Anderson, Charles R]

I'll also point out that CD/DVD devices are usually named /dev/sr0
/dev/sr1 etc. where the "sr" stands for "SCSI ROM" and the numbers 0,
1, etc. are not partitions, but actual different physical drives.
Older systems may use /dev/scd0, /dev/scd1, etc.

So in my request for output, you should also post this:

dmesg | grep 'sr[0-9]'

On Sat, Dec 29, 2018 at 11:51:24PM -0500, David Kramer wrote:
> I doubt the solution to that other person's problem is the same one you
> are having, but it's possible.  Let me explain it in more detail,
> because it actually has nothing to do with external DVD drives
> specifically, which is muddying the waters.
> 
> These days, most storage devices emulate the old SCSI (Small Computer
> System Interface) standard at the API level. That is, the hardware is
> different, but the commands that an OS or BIOS would send to an old SCSI
> drive.  That's why the devices are named /dev/sda, dev/sdb, etc.  The
> devices are named in order as they are discovered, so the main drive is
> /dev/sda, and if you have a second disk it would be /dev/sdb.
> 
> Partitions are named by appending the partition number to the device
> they are on.  The first partition on the first device is /dev/sda1, and
> the second partition would be /dev/sda2.
> 
> Let's say you plug in a thumb drive after that.  That would be the third
> disk, so it would be /dev/sdc.   If you then plugged in your external
> DVD drive, it would probably be /dev/sdd.  That all works pretty well.
> 
> Here's the problem: Let's say you have some configuration file, whatever
> it is, that refers to a disk, because you have a second hard drive in
> your computer.  let's call it /dev/sdb.  Now let's say you plug in your
> external DVD player and it comes up as /dev/sdc, and all is right with
> the world.
> 
> BUT: If you remove that second drive from your computer and there is no
> longer a /dev/sdb, and you do not update that configuration file, then
> when you add your external DVD player, it will come up as /dev/sdb
> instead.  That configuration file is telling your computer that /dev/sdb
> is something else.  And there we have the problem.
> 
> Now this file in particular, /etc/fstab (and you need to use sudo to
> edit it) tells the computer what each drive is for and how to mount it
> and to where.  It is a BAD file to have incorrect information in for
> that reason, and that is the problem described in your mail.  I doubt
> that's your problem, but if you send us the contents of that file, we
> may be able to confirm.
> 
> Some good news: There IS a better way. Partitions can also be identified
> by user-specified labels, and that eliminates the whole
> who-got-connected-first problem. It also lets you set up rules, like
> automatically mounting THIS particular external USB device, but not this
> other one.
> 
> Hope that helps.
> 
> 
> On 12/29/18 10:12 PM, Nancy Allison wrote:
> > Thank you, Dan.
> >
> > You've provided some details that I can follow, but I am not well enough
> > grounded to know how I would use them. (For example, I have no idea where
> > fstab lives or how I get to it.) If I can find someone to help me out
> > painstakingly, with a generous donation of their time and effort, I (they,
> > really) can undoubtedly fix the problem. I may wait until the next
> > InstallFest for help.
> >
> > But this leaves me wondering, can it really be that everyone using Fedora
> > 28 struggles along with this same problem that obviously affects plenty of
> > people? CDs and DVDs are not used as much as they once were, but they are
> > still in use. If you google "fedora 28 doesn't recognize external dvd
> > drive" you get people struggling with this back in 2010 and 2011. Is this
> > what Fedora is like -- everyone struggles with problems individually? And
> > you really have to have a lot of technical knowledge to deal with these
> > problems as they come up. Maybe Fedora is just too tecchie for me, but it
> > seems as if Ubuntu was, too, when I used it before Fedora. Maybe Red Hat is
> > easier for a non-technical person to handle?
> >
> > Just thinking out loud. Thanks for the additional info.
> >
> > On Sat, Dec 29, 2018 at 7:12 PM Dan Ritter <dsr at randomstring.org> wrote:
> >
> >> Nancy Allison wrote:
> >>> Hi, all.
> >>>
> >>> When I plug in my external disk drive into my Fedora 28 machine, it does
> >>> not show up in Nautilus.
> >>>
> >>> I go looking online, and, sure enough, this problem has occurred for
> >> plenty
> >>> of people for 5+ years over many releases of Fedora.
> >>>
> >>> I find a discussion in which someone evidently solved the problem. Here
> >> is
> >>> what the person reported:
> >>>
> >>> "NVM - found the cause. Old entry in fstab for a second swap not present
> >> on
> >>> sdb1 and first USB disks being assigned sdb. Cleaned that up and now all
> >>> drives plugging correctly.
> >>> Willtech ( Sep 23 '18 )"
> >>>
> >>> How do I apply this information? Where is fstab? When does a first swap
> >>> occur? When does a second swap occur? What does it mean to be assigned
> >> sdb?
> >>
> >> /etc/fstab consolidates mounting information.
> >>
> >> Each active line defines:
> >>
> >> <file system> <mount point>   <type>  <options>  <dump> <pass>
> >>
> >> For example:
> >>
> >> /dev/scd0   /media/cdrom0   ISO9660     ro      1   1
> >>
> >> device/partition name, then where you want it mounted, then the
> >> type of filesystem.
> >>
> >> If you have a single disk called /dev/sda, for instance, you
> >> might see your external CD show up as /dev/sdb. If there's
> >> already a /dev/sdb listed in the file, that will conflict.
> >>
> >> Hope that helps.
> >>
> >> -dsr-