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Old 01-22-2006, 06:47 PM   #1
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DVD writes bad data to disk when growisofs is executed from script

I used to perform backups to a cdrom, with a script that I wrote in python. My source code repository soon became to large to use a cdrom for backups, so I bought an external usb dvd writer(Memorex dual format dvd recorder), in the hopes that all I would have to do was change the backup media location in my script. Boy, was I naive! For months I have been trying to figure out why the same command that I type from the command line creates a perfectly readable dvd, but when I place the same command in a script and execute it through a system call I get an unreadable dvd. I thought the issue might be a python issue, so I wrote a shell script to do the same thing, and I had the same problem. Here is the command:

growisofs -dvd-compat -use-the-force-luke=tty -Z /dev/scd0 image.iso

*-use-the-force-luke -->I created a dvd using the gnome gui and this is one of the options that I saw when I typed ps -jx while the dvd was burning. I thought maybe I wasn't using the correct switches so I added this one.

OS: Fedora Core 3
Kernel: 2.6.9-1.667smp
mkisofs: 2.01 (i686-pc-linux-gnu) *This covers growisofs as well
Obviously, the dvd writer is being recognized...
Initializing USB Mass Storage driver...
scsi2 : SCSI emulation for USB Mass Storage devices
Vendor: Memorex Model: DVD+/-DLRWN16 D2 Rev: 2.AB
Type: CD-ROM ANSI SCSI revision: 02

def writeISO(isoPath, backupDevice):
cmd = 'growisofs -dvd-compat -use-the-force-luke=tty -Z %s %s' %\
(backupDevice, isoPath)

writeISO ()
cmd="growisofs -dvd-compat -use-the-force-luke=tty -Z $backupDevice $destPath"

Any ideas?
Old 01-23-2006, 01:43 PM   #2
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Further clarification

Basically, if I copy files to the Nautalis CD/DVD GUI in Fedora Core 3 and select create DVD I can produce readable isos. The gui makes the iso and burns the dvd all in one shot. However, if I type the same commands that I see by running ps when nautalis is creating the dvd I get a dvd that appears to be blank.
Old 03-25-2006, 11:29 AM   #3
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My previous post got trashed, I think, so this will be shorter.

growisofs will not overwrite an existing iso file system on a dvd if
one is running it from a non-interactive shell. It will overwrite an isofs
if you are running from an interactive shell. You also need to add some
mkisofs arguments, as growisofs is essentially a frontend to mkisofs.
The 'use-the-force-luke' flag can take a number of options, but the 'tty'
one overcomes the behavior described above. Here is the command line I userun out of cron nightly:

/usr/bin/growisofs -use-the-force-luke=tty -R -J $1 -Z $DVDRW_DRIVE

$1 is the file or directory to be backed up. -R and -J are options to mkisofs(8).

Options to use with the use-the-force-luke flag can be found in the growisofs
source code. I would put in the URL here, but that trashed my previous post,
so just google for it.

Old 03-25-2006, 11:32 AM   #4
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Further clarification on growisofs: re: my previous post,
I am using growisofs v5.21 on Fedora Core 4, on a generic brand USB dvdrw drive.
Old 04-17-2006, 05:30 PM   #5
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Thank you

I will give this a try and let you know how this works out.


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