Root/Documentation/cdrom/packet-writing.txt

1Getting started quick
2---------------------
3
4- Select packet support in the block device section and UDF support in
5  the file system section.
6
7- Compile and install kernel and modules, reboot.
8
9- You need the udftools package (pktsetup, mkudffs, cdrwtool).
10  Download from http://sourceforge.net/projects/linux-udf/
11
12- Grab a new CD-RW disc and format it (assuming CD-RW is hdc, substitute
13  as appropriate):
14    # cdrwtool -d /dev/hdc -q
15
16- Setup your writer
17    # pktsetup dev_name /dev/hdc
18
19- Now you can mount /dev/pktcdvd/dev_name and copy files to it. Enjoy!
20    # mount /dev/pktcdvd/dev_name /cdrom -t udf -o rw,noatime
21
22
23Packet writing for DVD-RW media
24-------------------------------
25
26DVD-RW discs can be written to much like CD-RW discs if they are in
27the so called "restricted overwrite" mode. To put a disc in restricted
28overwrite mode, run:
29
30    # dvd+rw-format /dev/hdc
31
32You can then use the disc the same way you would use a CD-RW disc:
33
34    # pktsetup dev_name /dev/hdc
35    # mount /dev/pktcdvd/dev_name /cdrom -t udf -o rw,noatime
36
37
38Packet writing for DVD+RW media
39-------------------------------
40
41According to the DVD+RW specification, a drive supporting DVD+RW discs
42shall implement "true random writes with 2KB granularity", which means
43that it should be possible to put any filesystem with a block size >=
442KB on such a disc. For example, it should be possible to do:
45
46    # dvd+rw-format /dev/hdc (only needed if the disc has never
47                                been formatted)
48    # mkudffs /dev/hdc
49    # mount /dev/hdc /cdrom -t udf -o rw,noatime
50
51However, some drives don't follow the specification and expect the
52host to perform aligned writes at 32KB boundaries. Other drives do
53follow the specification, but suffer bad performance problems if the
54writes are not 32KB aligned.
55
56Both problems can be solved by using the pktcdvd driver, which always
57generates aligned writes.
58
59    # dvd+rw-format /dev/hdc
60    # pktsetup dev_name /dev/hdc
61    # mkudffs /dev/pktcdvd/dev_name
62    # mount /dev/pktcdvd/dev_name /cdrom -t udf -o rw,noatime
63
64
65Packet writing for DVD-RAM media
66--------------------------------
67
68DVD-RAM discs are random writable, so using the pktcdvd driver is not
69necessary. However, using the pktcdvd driver can improve performance
70in the same way it does for DVD+RW media.
71
72
73Notes
74-----
75
76- CD-RW media can usually not be overwritten more than about 1000
77  times, so to avoid unnecessary wear on the media, you should always
78  use the noatime mount option.
79
80- Defect management (ie automatic remapping of bad sectors) has not
81  been implemented yet, so you are likely to get at least some
82  filesystem corruption if the disc wears out.
83
84- Since the pktcdvd driver makes the disc appear as a regular block
85  device with a 2KB block size, you can put any filesystem you like on
86  the disc. For example, run:
87
88    # /sbin/mke2fs /dev/pktcdvd/dev_name
89
90  to create an ext2 filesystem on the disc.
91
92
93Using the pktcdvd sysfs interface
94---------------------------------
95
96Since Linux 2.6.20, the pktcdvd module has a sysfs interface
97and can be controlled by it. For example the "pktcdvd" tool uses
98this interface. (see http://tom.ist-im-web.de/download/pktcdvd )
99
100"pktcdvd" works similar to "pktsetup", e.g.:
101
102    # pktcdvd -a dev_name /dev/hdc
103    # mkudffs /dev/pktcdvd/dev_name
104    # mount -t udf -o rw,noatime /dev/pktcdvd/dev_name /dvdram
105    # cp files /dvdram
106    # umount /dvdram
107    # pktcdvd -r dev_name
108
109
110For a description of the sysfs interface look into the file:
111
112  Documentation/ABI/testing/sysfs-block-pktcdvd
113
114
115Using the pktcdvd debugfs interface
116-----------------------------------
117
118To read pktcdvd device infos in human readable form, do:
119
120    # cat /sys/kernel/debug/pktcdvd/pktcdvd[0-7]/info
121
122For a description of the debugfs interface look into the file:
123
124  Documentation/ABI/testing/debugfs-pktcdvd
125
126
127
128Links
129-----
130
131See http://fy.chalmers.se/~appro/linux/DVD+RW/ for more information
132about DVD writing.
133

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