# External DVD burner USB

## jrembold

Hiya,

I've been looking for the answer to this on for about two hours.

Trying to get me external burner to work:

dmesg: (the important part)

```
usb 1-4: new high speed USB device using ehci_hcd and address 2

scsi0 : SCSI emulation for USB Mass Storage devices

usb-storage: device found at 2

usb-storage: waiting for device to settle before scanning

  Vendor: Memorex   Model: DVD+/-RW True8Xn  Rev: 1.G1

  Type:   CD-ROM                             ANSI SCSI revision: 00

Attached scsi generic sg0 at scsi0, channel 0, id 0, lun 0,  type 5

usb-storage: device scan complete

usb 1-4: USB disconnect, address 2

usb 1-4: new high speed USB device using ehci_hcd and address 3

scsi1 : SCSI emulation for USB Mass Storage devices

usb-storage: device found at 3

usb-storage: waiting for device to settle before scanning

  Vendor: Memorex   Model: DVD+/-RW True8Xn  Rev: 1.G1

  Type:   CD-ROM                             ANSI SCSI revision: 00

Attached scsi generic sg0 at scsi1, channel 0, id 0, lun 0,  type 5

usb-storage: device scan complete
```

fstab:

```
/dev/hda1               /boot           ext3            noauto,noatime  1 2

/dev/hda3               /               ext3            noatime         0 1

/dev/hda2               none            swap            sw              0 0

/dev/hdc                /mnt/cdrom      auto            noauto,user,ro  0 0

#/dev/fd0               /mnt/floppy     auto            noauto          0 0

usbfs                   /proc/bus/usb   usbfs           devgid=14,devmode=0660  0 0

# NOTE: The next line is critical for boot!

none                    /proc           proc            defaults        0 0

none                    /dev/shm        tmpfs           defaults        0 0

/dev/sda2               /mnt/ipod       vfat            nosuid,user,rw,noauto   0 0

/dev/sda1               /mnt/dvdrw      auto            defaults,user,noauto,ro,exec    0 0

```

I'm totally at a loss.

Also, Nero can't find my internal cdr-w to burn regular cds.  I'm thinking that too has to do with fstab.

jrembold

----------

## morodoch

 *Quote:*   

> /dev/sda2               /mnt/ipod       vfat            nosuid,user,rw,noauto   0 0
> 
> /dev/sda1               /mnt/dvdrw      auto            defaults,user,noauto,ro,exec    0 0 

 

I'd expect your dvd drive to show up as the whole device (/dev/sda or /dev/sdb) and your ipod to show up as a partition on the other one (/dev/sdb1 or /dev/sda1).

----------

## jrembold

so, instead of sda1, change it to sda or sdb?

jrembold

----------

## jrembold

i tried it with no dice.  next part of the question, why doesn't nero recognize my internal cdr-w burner?

jrembold

----------

## morodoch

SCSI devices and USB storage devices are given devices /dev/sda, /dev/sdb, /dev/sdc, /dev/sd... in the order they're discovered, I think.

While /dev/sd<some letter> refers to the whole device, /dev/sd<some letter><some number> refers to a partition on the device.

DVD / CD drives present the whole disc at once, so you use the /dev/sd<some letter> device, where hard drives have partitions, so you use /dev/sd<some letter><some number>.

Now the only difficulty left is working out which letters and numbers to use   :Shocked: 

If you have other devices on you machine, it may be /dev/sdd and /dev/sde (for example); I guess a bit of trial and error may be in order.

The other thing that you'll need to look out for is permissions - you'll need to be in the appropriate groups to access the devices unless you're running as root (not generally recommended, but you might want to try it to see if it's a permissions thing).

----------

## dsd

"sd" devices are scsi disk devices. cdroms dont fall into this category.

you need to enable SCSI cdrom in your kernel config, and then you'll get a node such as /dev/scd0 (or /dev/sr0 ?) which is mountable

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## morodoch

 *Quote:*   

> "sd" devices are scsi disk devices. cdroms dont fall into this category. 

 

Good point!

I think to record, you'll actually end up with /dev/sg devices ("scsi generic") - one for each of your /dev/sr device. In fact, thinking about it, you probably need to also include the scsi generic device driver in your kernel.

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## dsd

yes, you'll also get sg devices (and if you look in the first post you can see that this is already happening) however these are unmountable and (probably) unncessary for standard cdrom usage

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## morodoch

OK, but from what I remember the last time I used a real SCSI drive, you used the /dev/sr devices to mount and the /dev/sg devices to write - I don't know if the modern desktop tools do this handling for you.

So from the original post:

 *Quote:*   

> /dev/sda2               /mnt/ipod       vfat            nosuid,user,rw,noauto   0 0
> 
> /dev/sda1               /mnt/dvdrw      auto            defaults,user,noauto,ro,exec    0 0 

 

I still think this looks wrong - one of these ought to be then /dev/sr0, and the other /dev/sda1 (or 2?).

As far as recording goes, nero ought to point to /dev/sg0.

If this is all happening, I guess the most likely cause of any problems is permissions. Are you in the cdrom and cdrw groups?

----------

## drphibes

I have a Memorex external usb dvd/cd burner.   I use udev-70-r1 (latest stable).  udev creates /dev/sr0 for me and these symlinks:

```
lrwxrwxrwx  1 root root         3 Dec 16 12:26 cdrom1 -> sr0

lrwxrwxrwx  1 root root         3 Dec 16 12:26 cdrw -> sr0

lrwxrwxrwx  1 root root         3 Dec 16 12:26 dvd -> sr0

lrwxrwxrwx  1 root root         3 Dec 16 12:26 dvdrw -> sr0

brw-rw----  1 root cdrw   11,   0 Dec 16 12:26 sr0

```

The only custom udev rule I use is one to put sr0 into group cdrw:

```
# put cd rw-capable devices into group cdrw

ENV{ID_CDROM_CD_RW}=="?*",  GROUP="cdrw"
```

I also have generic scsi support in the kernel too for the /dev/sgX devices.

The only fstab entry I have for it is this noauto entry:

```
/dev/dvd      /mnt/dvd           iso9660      noauto,user,ro                        0 0
```

which I use to mount iso's.

Works with no problems at all.

----------

## jrembold

 *drphibes wrote:*   

> I have a Memorex external usb dvd/cd burner.   I use udev-70-r1 (latest stable).  udev creates /dev/sr0 for me and these symlinks:
> 
> ```
> lrwxrwxrwx  1 root root         3 Dec 16 12:26 cdrom1 -> sr0
> 
> ...

 

How do I do these?  I'm still learning... I feel like a small child.

jrembold

----------

## jrembold

OK, I got it to work in NERO.  It's nice, however, I still can't mount the DVD drive.

Here's my fstab that worked:

```
/dev/sg0                /mnt/dvd        iso9660         user,noauto,ro  0 0

```

I get 

```
mount: /dev/sg0 is not a block device
```

I also cannot access my cdrom like I used to.

jrembold

----------

## drphibes

there are many different contexts in which such a dvd/cd burner/player can be used.   depending on the context, you may or may not need to actually mount the drive.   also, the generic scsi devices /dev/sg0 is used only in special (rare) situations, such as for cdrecord.   it gets a little complicated for someone totally new to linux to understand.   you only need to mount a dvd if it contains a filesystem that's appropriate for mounting.   when you try to mount an iso9660 dvd, you are mounting a _data_ dvd that contains an iso9660 filesystem you wish to latch onto your filesystem for browsing files.   film dvd's, on the other hand, contain no mountable filesystems per se.   in this case, you simply need a symlink, /dev/dvd, to your dvd device (/dev/sr not /dev/sg) and the video player (mplayer, xine, etc) "knows" how to read the data on the dvd device.   again, you do not mount video dvd's, only data dvd's.

to review, you should have an /dev/sr0 device for this external usb burner.  if you don't, you need to find out why.  one likely reason may be that you do not have  the block device SR config'd in your kernel.  make sure, under SCSI Device Support, you have configured SCSI CDROM support.  I set it to 'm' for module (sr_mod).   The entry on your /usr/src/linux/.config would be:  CONFIG_BLK_DEV_SR=m.    The command 'lsmod' will show you which modules are loaded.  If you do not see sr_mod, type 'modprobe sr_mod' as root to load the module.  At that point, udev will create /dev/sr0 and several symlinks for you.

Remember, avoid the generic scsi device, you only need that for cdrecord and don't try to mount video dvd's.

----------

