cdfs, cddb - optical disc (CD, DVD, BD) track reader and writer file
SYNOPSIScdfs [ -d sddev ] [ -m mtpt ]
grep aux/cddb /mnt/cd/ctl | rc
aux/cddb [ -DTt ] [ -s server ] query diskid ntracks track0id ...
Cdfs serves a one and a half level directory mounted at mtpt (default
/mnt/cd) that provides access to the tracks on discs placed in the disc
reader or writer named by sddev (default /dev/sdD0, see sd(3)). Any
MMC-compliant compact disc (CD), DVD, or Blu-ray disc (BD) drive should
work. On DVDs and BDs, access to data tracks only is implemented.
The top level directory contains one file per disc track. The files
are named cNNN, where c is a type character (a for audio tracks and d
for data tracks) and NNN is the track number.
If the device can write discs and contains a writable disc, the top-
level directory also contains an empty directory wd and, for CDs only,
an empty directory wa. Files created in these directories appear in
the top-level directory as new data or audio tracks, respectively,
regardless of name.
At any time, any number of tracks may be open for reading or a single
track may be open for writing. Writing a disc track is a quasi-real-
time operation: the disc writer should be kept saturated with new data
to avoid buffer underruns, but modern drives will be told to cope with
underruns transparently. To ensure saturation, copying from a file
system stored on local disk or memory is recommended.
BD-R discs are `formatted' upon first use, for sequential writing with
spare sectors for hardware defect management, so BD drives should not
report errors when writing BD-R discs; any such errors may be a sign
that the laser of an old drive is fading.
To fixate a disc (close a recordable disc by writing its permanent ta‐
ble of contents), simply remove the wa or wd directory. The directory
removed selects whether the disc is fixated as an audio or data disc;
since each track carries its own type information, very few readers
care which fixation type was used. Rewritable discs do not require
The top level directory also contains a ctl file, into which control
messages may be echoed. The current control messages are:
format Format the rewritable disc (-RW or -RE) in the drive before ini‐
blank Blank the entire rewritable disc in the drive.
Blank only the table of contents on the rewritable disc in the
eject Eject the disc in the drive.
ingest Ingest a disc into the drive.
Set the reading and writing speed to use, in units of
1,000-bytes-per-second. A value of requests the optimal speed
for the current drive and disc. CD speed is 154; DVD speed is
1350; BD speed is 4608. Drives may round down the speed to one
they support. To set reading and writing speeds separately,
prefix the speeds with read or write, as in speed write 8192 or
speed read 16384 write 8192. Note that most drives reset the
reading and writing speed each time a new disc is inserted.
Reading the ctl file yields information about the drive. If the drive
contains an audio CD, the first line will be an aux/cddb command that
can be run to query an internet CD database to get a table of contents.
Subsequent lines contain the current and maximum reading and writing
speeds. Additional lines may further describe the current disc.
Aux/cddb takes 4 optional arguments. The -s option makes aux/cddb use
server for the query instead of The -D option causes the raw database
response from the server to be dumped to standard output. The -t
option causes the time of each track to be appended to the normal out‐
put. -T is like -t but prints a final line with the total time.
Backup to a BD-R disc:
tar cf /mnt/cd/wd/x /n/boot
Copy the audio tracks from a CD:
cp /mnt/cd/a* /tmp/songs
Copy the tracks onto a blank CD inserted in the drive, and then fixate
the disk as an audio CD.
cp /tmp/songs/* /mnt/cd/wa
SEE ALSOpump(1), sd(3), 9660srv (in dossrv(4)), mk9660(8)
optical disc interface standards, notably Multi-Media Commands
Fixating a BD-R disc records only the first track in the disc's TOC.
Any other tracks are still there and their data accessible via sd(3).
There's no need to fixate data discs, except to prevent adding new
Closing a just-written DVD-R track can take minutes while the drive
burns the unused part of the track reservation (for the whole disc).
Thus only a single DVD-R track can be written on a DVD-R disc; use
other media if you need more than one track per disc.
There are too many combinations of optical media, each with unique
quirks, approximately the cross-product of these tuples: (CD DVD- DVD+
BD), (-ROM -R -RW), (single-layer dual-layer), plus oddities like DVD-
RAM. Triple- and quad-layer BD drives and discs are starting to
Only MMC-compliant disc readers and writers are supported, but it would
be easy to add support for early CD writers if desired.
Cdfs can take some seconds to figure out that it has a BD in the drive
and how many layers are on the disc.