Dvd and Cd

cd

finding the cd drive

cdrecord -scanbus You get a list like :

scsibus2:
    2,0,0   200) 'ATA     ' 'SAMSUNG HD502IJ ' '1AA0' Disk
    2,1,0   201) *
    2,2,0   202) *
    2,3,0   203) *
    2,4,0   204) *
    2,5,0   205) *
    2,6,0   206) *
    2,7,0   207) *
scsibus4:
    4,0,0   400) 'LITE-ON ' 'DVD SOHD-167T   ' '9S19' Removable CD-ROM
    4,1,0   401) 'LITE-ON ' 'LTR-12101B      ' 'LS38' Removable CD-ROM
    4,2,0   402) *
    4,3,0   403) *
    4,4,0   404) *
    4,5,0   405) *
    4,6,0   406) *
    4,7,0   407) *

Decide on the one you want to use and remember the number.

Burning the image

So burning it to 'LITE-ON' 'LTR-12101B' would mean :

cdrecord -v dev=4,1,0 WXPVOL_EN.iso

dvd

ripping dvd

dd if=/dev/cdrom of=/path/to/cdcopy.iso

Or find out what the dvd device is, on power you need :

dd if=/dev/sr0 of=/path/to/cdcopy.iso

burning (copying) dvd's

This is an ultrashort description of how to burn dvd's on linux: install growisofs

apt-get install dvd+rw-tools

get the data from the dvd as a whole

cat /dev/hda > big.iso

burning the image

growisofs -Z /dev/cdrom=big.iso

If you want to burn a '''directory''':

growisofs -Z /dev/dvd -R -J /dir/file-name

Note that a command like this :

growisofs -Z /dev/dvd -R -J big.iso

Will not burn the image to disk but will make a dvd with big.iso on it as the only file

multi session

An easy way to make more use of a dvd's capacity for instance for backup is to incrementally write multiple sessions to the dvd.

You can actually mount the dvd and make it behave like a normal filesystem. For instance if you write file a in session 1 and file b in session 2 you get both of them in the same directory. Even deletion is possible, though i did not try it.

In my case i actually rather have all copies of the backups available so putting them in different directories with a file stamp works just as well.

starting

The first session is special, and should be started like this.

growisofs -Z /dev/sr0 -R -J /var/lib/aide

This burns the files inside the aide directory to the root of the cdrom, it does NOT create the aide directory as well.

mount /media/cdrom
ls /media/cdrom
# output :
aide.conf.autogenerated  aide.db  aide.db.new

more sessions

After that you can add sessions with -M (multi ?)

growisofs -M /dev/sr0 -R -J /var/lib/tripwire

Now you have a disk with two sessions, and two alternatives to mounting the dvd. You can steer that with the session mount option. In /etc/fstab

/dev/sr0        /media/cdrom0   udf,iso9660 user,noauto,ro,session=0     0       0
# umount /media/cdrom
# mount /media/cdrom
# ls /media/cdrom
# aide.conf.autogenerated  aide.db  aide.db.new

So this gives the state at session 0, only aide files are visible.

/dev/sr0        /media/cdrom0   udf,iso9660 user,noauto,ro,session=0     0       0
# umount /media/cdrom
# mount /media/cdrom
# ls /media/cdrom
# aide.conf.autogenerated  aide.db.new  colatic.twd.bak
# aide.db                  colatic.twd  report

As you see, now both sessions appear in the same directory.

It seems only session 0 can be retrieved like this. All other sessions are merged into one after that no matter what you fill in session=[1-x]

examining sessions

You can get a lot of info by installing and using dvd+rw-tools :

apt-get install dvd+rw-tools
dvd+rw-mediainfo

This will list all written tracks and where they reside. It is important to find out if you can isolate a single track or at least a snapshot from earlier. This because a compromised system may be used to destroy the dvd attached and we still end up with no backup.

To get any session you want use this method :

dvd+rw-mediainfo | grep Start
Track Start Address:   0*2KB
Track Start Address:   93952*2KB
Track Start Address:   102736*2KB
Track Start Address:   109088*2KB
Track Start Address:   115440*2KB
Track Start Address:   121792*2KB

Now you will have to guess which one, or just try multiple times. Take the address and mount your section with this commandline :

mkdir dvd
mount -o sbsector=102736 /dev/sr0 dvd

You will now have the correct 'snapshot' up to that point, not the separate write done. I added the aide configuration files only once in the very first session, and these files will be present in all mounts !! Still this suffices for me, and i will do daily backups to be able to fixate this dvd as soon as possible.

These commands do not work on CD media only DVD. You could try similar operations with wodim and or xorriso.