udftools for Debian =================== Kernel support for packet writing --------------------------------- Packet writing is a technique by which a writable medium (typically a CD or DVD) can be used just like a USB stick or a directory on the hard disc: Files and directories can be created/renamed/removed freely, and no separate "burning" step is necessary to write the data to the medium. Packet writing is possible both with write-once media (CD-R, DVD+R, DVD-R) and rewritable media (CD-RW, DVD+RW, DVD-RW). Obviously, with write-once media the free space on the filesystem will not increase if you delete files. In order to do packet writing under Debian Linux, your kernel needs both support for UDF (Universal Disc Format) filesystems and for packet writing. This is the case for kernels later than about 2.6.10. For earlier kernels, you may have to apply patches from Peter Osterlund . That site also has patches for udftools to make them work with recent kernels - they have been applied to this package. This package tries to support both old-style packet writing (kernel <2.6.8), and the newer variant (>=2.6.10), with and without udev. Use a recent 2.6 kernel for optimal results! Formatting and using a UDF DVD-RW or CD-RW for packet writing ------------------------------------------------------------- The commands differ depending on whether you are using DVD or CD media. 1) Edit /etc/default/udftools and add your drive for packet writing. For example, if your CD/DVD writer is /dev/hdc and you want it available as the default /dev/pktcdvd/0, then use the setting "DEVICES=/dev/hdc". Execute "/etc/init.d/udftools start" afterwards to register the device. If the device name /dev/hdc differs on your system, adjust the following commands as appropriate. 2) Prepare the medium in restricted overwrite mode: DVD-RW: dvd+rw-format -force /dev/hdc CD-RW: Do nothing, skip this step! 3) Write an empty session spanning the whole medium. It seems that without this step, any attempt to create the UDF filesystem will fail. DVD-RW: growisofs -Z /dev/hdc=/dev/zero CD-RW: cdrwtool -d /dev/hdc -q 4) Format the packet device in UDF format. DVD-RW: mkudffs --udfrev=0x0150 --spartable=2 --media-type=dvdrw /dev/pktcdvd/0 CD-RW: mkudffs --udfrev=0x0150 --spartable=2 --media-type=cdrw /dev/pktcdvd/0 The parameters require some more explanation: For --udfrev, use either 0x0150 for UDF version 1.50, or 0x0201 for UDF version 2.01. The version decision has mostly to do with compatibility: - Windows 98/ME can read up to v1.02 - Windows 2000, Mac OS 9, Linux 2.4 can read up to v1.50 - Windows 2003/XP can read up to v2.01 - Linux 2.6 can read up to v2.60 For normal data, UDF 1.50 is OK. UDF 2.00 and 2.01 introduce additional functionality for streaming audio/video. Possible values for --media-type are: hd dvdram dvdrw worm mo cdrw cdr. Use the one appropriate for your medium/device. 5) Mount the disc. The "noatime" option is important: It will reduce the amount of writes to the device and thus increase its lifetime. You may first have to create the mount directory using "mkdir /media/dvd0": mount -t udf -o rw,noatime /dev/pktcdvd/0 /media/dvd0 The "sync" mount option might also be useful, but will typically cause an increased number of write accesses to the medium. From now on, the root user can access the filesystem under /media/dvd0 using read and write operations. 6) If regular users should also have write access, modify the permissions as follows _while the filesystem is mounted_: chgrp plugdev /media/dvd0 # Set group ownership to "plugdev" chmod g+rwx /media/dvd0 # Give full read/write access to group Now all users who should have access to the disc need to be added to the "plugdev" group using "adduser plugdev". To also allow these users to mount and unmount/eject the medium, you can use either of these two routes: - Install the "pmount" package and add the device to the list of allowed devices using "echo /dev/pktcdvd/0 >>/etc/pmount.allow". All members of the group "plugdev" will then be able to mount the disc using "pmount /dev/pktcdvd/0 dvd0" and unmount it using "pumount /media/dvd0". - Add a line like the following to /etc/fstab: /dev/pktcdvd/0 /media/dvd0 udf rw,noatime,users,noauto 0 0 This will enable _all_ users to mount the disc using "mount /media/dvd0" and unmount it with "umount /media/dvd0". However, with the permissions from step 5) above, only the members of group "plugdev" ought to be able to write to it. Support for UDF filesystems --------------------------- UDF (not packet writing) support in Linux 2.4 and later kernels is sufficient to read from and write to UDF filesystems. For example, you can create a regular file, "format" it using mkudffs, and then loop-mount it. To do this, execute the following commands as root: (After "count=", supply the required size in MB of the filesystem.) dd if=/dev/zero of=udfimage bs=1M count=10 mkudffs udfimage mkdir udfmnt mount -o loop -t udf udfimage udfmnt You need Linux 2.4+ with UDF read *and* write support enabled. Now you can copy data to the "udfmnt" directory. After an "umount udfmnt", the file "udfimage" could theoretically be written to a CD-R(W) or DVD-R(W). In practice, you will not want to do that, as the whole point of using UDF is to do packet writing. -- Richard Atterer Wed, 22 Nov 2006 23:38:16 +0100